[1080241] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[6732c094] | 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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[1080241] | 4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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| 7 |
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| 8 | <sect1 id="unpacking">
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[82c65b7] | 9 | <?dbhtml filename="notes-on-building.html"?>
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[1080241] | 10 |
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| 11 |
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| 12 | <title>Notes on Building Software</title>
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| 13 |
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| 14 | <para>Those people who have built an LFS system may be aware
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[ec64d28] | 15 | of the general principles of downloading and unpacking software. Some
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| 16 | of that information is repeated here for those new to building
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[1080241] | 17 | their own software.</para>
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| 18 |
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| 19 | <para>Each set of installation instructions contains a URL from which you
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[ec64d28] | 20 | can download the package. The patches; however, are stored on the LFS
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| 21 | servers and are available via HTTP. These are referenced as needed in the
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| 22 | installation instructions.</para>
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[1080241] | 23 |
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| 24 | <para>While you can keep the source files anywhere you like, we assume that
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| 25 | you have unpacked the package and changed into the directory created by the
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| 26 | unpacking process (the 'build' directory). We also assume you have
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| 27 | uncompressed any required patches and they are in the directory immediately
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| 28 | above the 'build' directory.</para>
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| 29 |
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| 30 | <para>We can not emphasize strongly enough that you should start from a
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| 31 | <emphasis>clean source tree</emphasis> each time. This means that if
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| 32 | you have had an error during configuration or compilation, it's usually
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| 33 | best to delete the source tree and
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| 34 | re-unpack it <emphasis>before</emphasis> trying again. This obviously
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| 35 | doesn't apply if you're an advanced user used to hacking
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| 36 | <filename>Makefile</filename>s and C code, but if in doubt, start from a
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| 37 | clean tree.</para>
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| 38 |
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| 39 | <sect2>
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| 40 | <title>Building Software as an Unprivileged (non-root) User</title>
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| 41 |
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| 42 | <para>The golden rule of Unix System Administration is to use your
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| 43 | superpowers only when necessary. Hence, BLFS recommends that you
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| 44 | build software as an unprivileged user and only become the
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| 45 | <systemitem class='username'>root</systemitem> user when installing the
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| 46 | software. This philosophy is followed in all the packages in this book.
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| 47 | Unless otherwise specified, all instructions should be executed as an
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| 48 | unprivileged user. The book will advise you on instructions that need
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| 49 | <systemitem class='username'>root</systemitem> privileges.</para>
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| 50 |
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| 51 | </sect2>
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| 52 |
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| 53 | <sect2>
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| 54 | <title>Unpacking the Software</title>
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| 55 |
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| 56 | <para>If a file is in <filename class='extension'>.tar</filename> format
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| 57 | and compressed, it is unpacked by running one of the following
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| 58 | commands:</para>
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| 59 |
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| 60 | <screen><userinput>tar -xvf filename.tar.gz
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| 61 | tar -xvf filename.tgz
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| 62 | tar -xvf filename.tar.Z
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| 63 | tar -xvf filename.tar.bz2</userinput></screen>
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| 64 |
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| 65 | <note>
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| 66 | <para>You may omit using the <option>v</option> parameter in the commands
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| 67 | shown above and below if you wish to suppress the verbose listing of all
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| 68 | the files in the archive as they are extracted. This can help speed up the
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| 69 | extraction as well as make any errors produced during the extraction
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| 70 | more obvious to you.</para>
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| 71 | </note>
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| 72 |
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| 73 | <para>You can also use a slightly different method:</para>
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| 74 |
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| 75 | <screen><userinput>bzcat filename.tar.bz2 | tar -xv</userinput></screen>
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| 76 |
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| 77 | <para>Finally, you sometimes need to be able to unpack patches which are
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| 78 | generally not in <filename class='extension'>.tar</filename> format. The
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[4d3e5f1] | 79 | best way to do this is to copy the patch file to the parent of the 'build'
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[1080241] | 80 | directory and then run one of the following commands depending on whether
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| 81 | the file is a <filename class='extension'>.gz</filename> or <filename
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| 82 | class='extension'>.bz2</filename> file:</para>
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| 83 |
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| 84 | <screen><userinput>gunzip -v patchname.gz
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| 85 | bunzip2 -v patchname.bz2</userinput></screen>
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| 86 |
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| 87 | </sect2>
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| 88 |
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| 89 | <sect2>
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[6333296] | 90 | <title>Verifying File Integrity</title>
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[1080241] | 91 |
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[6333296] | 92 | <para>Generally, to verify that the downloaded file is complete,
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[1080241] | 93 | many package maintainers also distribute md5sums of the files. To verify the
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| 94 | md5sum of the downloaded files, download both the file and the
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| 95 | corresponding md5sum file to the same directory (preferably from different
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| 96 | on-line locations), and (assuming <filename>file.md5sum</filename> is the
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| 97 | md5sum file downloaded) run the following command:</para>
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| 98 |
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| 99 | <screen><userinput>md5sum -c file.md5sum</userinput></screen>
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| 100 |
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| 101 | <para>If there are any errors, they will be reported. Note that the BLFS
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| 102 | book includes md5sums for all the source files also. To use the BLFS
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| 103 | supplied md5sums, you can create a <filename>file.md5sum</filename> (place
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| 104 | the md5sum data and the exact name of the downloaded file on the same
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| 105 | line of a file, separated by white space) and run the command shown above.
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| 106 | Alternately, simply run the command shown below and compare the output
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| 107 | to the md5sum data shown in the BLFS book.</para>
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| 108 |
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[57b11363] | 109 | <screen><userinput>md5sum <replaceable><name_of_downloaded_file></replaceable></userinput></screen>
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[1080241] | 110 |
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[6333296] | 111 | <para>MD5 is not cryptographically secure, so the md5sums are only
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[97ba425] | 112 | provided for detecting unmalicious changes to the file content. For
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| 113 | example, an error or truncation introduced during network transfer, or
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| 114 | a <quote>stealth</quote> update to the package from the upstream
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| 115 | (updating the content of a released tarball instead of making a new
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| 116 | release properly).</para>
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| 117 |
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| 118 | <para>There is no <quote>100%</quote> secure way to make
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[6333296] | 119 | sure the genuity of the source files. Assuming the upstream is managing
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| 120 | their website correctly (the private key is not leaked and the domain is
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| 121 | not hijacked), and the trust anchors have been set up correctly using
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| 122 | <xref linkend="make-ca"/> on the BLFS system, we can reasonably trust
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| 123 | download URLs to the upstream official website
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| 124 | <emphasis role="bold">with https protocol</emphasis>. Note that
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| 125 | BLFS book itself is published on a website with https, so you should
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| 126 | already have some confidence in https protocol or you wouldn't trust the
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| 127 | book content.</para>
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| 128 |
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| 129 | <para>If the package is downloaded from an unofficial location (for
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| 130 | example a local mirror), checksums generated by cryptographically secure
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| 131 | digest algorithms (for example SHA256) can be used to verify the
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| 132 | genuity of the package. Download the checksum file from the upstream
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| 133 | <emphasis role="bold">official</emphasis> website (or somewhere
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| 134 | <emphasis role="bold">you can trust</emphasis>) and compare the
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[2c87187] | 135 | checksum of the package from unofficial location with it. For example,
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[6333296] | 136 | SHA256 checksum can be checked with the command:</para>
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| 137 |
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| 138 | <note>
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| 139 | <para>If the checksum and the package are downloaded from the same
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| 140 | untrusted location, you won't gain security enhancement by verifying
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| 141 | the package with the checksum. The attacker can fake the checksum as
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| 142 | well as compromising the package itself.</para>
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| 143 | </note>
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| 144 |
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| 145 | <screen><userinput>sha256sum -c <replaceable>file</replaceable>.sha256sum</userinput></screen>
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| 146 |
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| 147 | <para>If <xref linkend="gnupg2"/> is installed, you can also verify the
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| 148 | genuity of the package with a GPG signature. Import the upstream GPG
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| 149 | public key with:</para>
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| 150 |
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| 151 | <screen><userinput>gpg --recv-key <replaceable>keyID</replaceable></userinput></screen>
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| 152 |
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| 153 | <para><replaceable>keyID</replaceable> should be replaced with the key ID
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| 154 | from somewhere <emphasis role="bold">you can trust</emphasis> (for
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| 155 | example, copy it from the upstream official website using https). Now
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| 156 | you can verify the signature with:</para>
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| 157 |
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| 158 | <screen><userinput>gpg --recv-key <replaceable>file</replaceable>.sig <replaceable>file</replaceable></userinput></screen>
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| 159 |
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| 160 | <para>The advantage of <application>GnuPG</application> signature is,
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| 161 | once you imported a public key which can be trusted, you can download
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| 162 | both the package and its signature from the same unofficial location and
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| 163 | verify them with the public key. So you won't need to connect to the
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| 164 | official upstream website to retrieve a checksum for each new release.
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| 165 | You only need to update the public key if it's expired or revoked.
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| 166 | </para>
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| 167 |
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[1080241] | 168 | </sect2>
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| 169 |
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| 170 | <sect2>
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| 171 | <title>Creating Log Files During Installation</title>
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| 172 |
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| 173 | <para>For larger packages, it is convenient to create log files instead of
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| 174 | staring at the screen hoping to catch a particular error or warning. Log
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| 175 | files are also useful for debugging and keeping records. The following
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| 176 | command allows you to create an installation log. Replace
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[57b11363] | 177 | <replaceable><command></replaceable> with the command you intend to execute.</para>
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[1080241] | 178 |
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[57b11363] | 179 | <screen><userinput>( <replaceable><command></replaceable> 2>&1 | tee compile.log && exit $PIPESTATUS )</userinput></screen>
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[1080241] | 180 |
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| 181 | <para><option>2>&1</option> redirects error messages to the same
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| 182 | location as standard output. The <command>tee</command> command allows
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| 183 | viewing of the output while logging the results to a file. The parentheses
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| 184 | around the command run the entire command in a subshell and finally the
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| 185 | <command>exit $PIPESTATUS</command> command ensures the result of the
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[57b11363] | 186 | <replaceable><command></replaceable> is returned as the result and not the
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[1080241] | 187 | result of the <command>tee</command> command.</para>
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| 188 |
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| 189 | </sect2>
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| 190 |
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[82c65b7] | 191 | <sect2 id="parallel-builds" xreflabel="Using Multiple Processors">
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| 192 | <title>Using Multiple Processors</title>
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| 193 |
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| 194 | <para>For many modern systems with multiple processors (or cores) the
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| 195 | compilation time for a package can be reduced by performing a "parallel
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| 196 | make" by either setting an environment variable or telling the make program
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| 197 | how many processors are available. For instance, a Core2Duo can support two
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| 198 | simultaneous processes with: </para>
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| 199 |
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| 200 | <screen><userinput>export MAKEFLAGS='-j2'</userinput></screen>
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| 201 |
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| 202 | <para>or just building with:</para>
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| 203 |
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| 204 | <screen><userinput>make -j2</userinput></screen>
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| 205 |
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[a334dd2a] | 206 | <para>
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| 207 | If you have applied the optional <command>sed</command> when building
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| 208 | <application>ninja</application> in LFS, you can use:
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| 209 | </para>
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| 210 |
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| 211 | <screen><userinput>export NINJAJOBS=2</userinput></screen>
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| 212 |
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| 213 | <para>
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| 214 | when a package uses <command>ninja</command>, or just:
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| 215 | </para>
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| 216 |
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| 217 | <screen><userinput>ninja -j2</userinput></screen>
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| 218 |
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| 219 | <para>
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| 220 | but for ninja, the default number of jobs is <N>+2, where <N>
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| 221 | is the number of processors available, so that using the above commands
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| 222 | is rather for limiting the number of jobs (see below for why this could
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| 223 | be necessary).
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| 224 | </para>
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| 225 |
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[82c65b7] | 226 | <para>Generally the number of processes should not exceed the number of
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| 227 | cores supported by the CPU. To list the processors on your
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| 228 | system, issue: <userinput>grep processor /proc/cpuinfo</userinput>.
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| 229 | </para>
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| 230 |
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[a334dd2a] | 231 | <para>In some cases, using multiple processes may result in a 'race'
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[82c65b7] | 232 | condition where the success of the build depends on the order of the
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| 233 | commands run by the <command>make</command> program. For instance, if an
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[ea20da9] | 234 | executable needs File A and File B, attempting to link the program before
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[82c65b7] | 235 | one of the dependent components is available will result in a failure.
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| 236 | This condition usually arises because the upstream developer has not
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[30203c2c] | 237 | properly designated all the prerequisites needed to accomplish a step in the
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[82c65b7] | 238 | Makefile.</para>
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| 239 |
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| 240 | <para>If this occurs, the best way to proceed is to drop back to a
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| 241 | single processor build. Adding '-j1' to a make command will override
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[a334dd2a] | 242 | the similar setting in the <envar>MAKEFLAGS</envar> environment
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| 243 | variable.</para>
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[82c65b7] | 244 |
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[e58667e] | 245 | <note><para>When running the package tests or the install portion of the
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| 246 | package build process, we do not recommend using an option greater than
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| 247 | '-j1' unless specified otherwise. The installation procedures or checks
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| 248 | have not been validated using parallel procedures and may fail with issues
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| 249 | that are difficult to debug.</para></note>
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| 250 |
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[a334dd2a] | 251 | <important>
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| 252 | <para>
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| 253 | Another problem may occur with modern CPU's, which have a lot of cores.
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| 254 | Each job started consumes memory, and if the sum of the needed
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| 255 | memory for each job exceeds the available memory, you may encounter
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| 256 | either an OOM (Out of Memory) kernel interrupt or intense swapping
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| 257 | that will slow the build beyond reasonable limits.
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| 258 | </para>
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| 259 |
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| 260 | <para>
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| 261 | Some compilations with <command>g++</command> may consume up to 2.5 GB
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| 262 | of memory, so to be safe, you should restrict the number of jobs
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| 263 | to (Total Memory in GB)/2.5, at least for big packages such as LLVM,
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| 264 | WebKitGtk, QtWebEngine, or libreoffice.
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| 265 | </para>
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| 266 | </important>
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[82c65b7] | 267 | </sect2>
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| 268 |
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[1080241] | 269 | <sect2 id="automating-builds" xreflabel="Automated Building Procedures">
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| 270 | <title>Automated Building Procedures</title>
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| 271 |
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| 272 | <para>There are times when automating the building of a package can come in
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| 273 | handy. Everyone has their own reasons for wanting to automate building,
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| 274 | and everyone goes about it in their own way. Creating
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| 275 | <filename>Makefile</filename>s, <application>Bash</application> scripts,
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| 276 | <application>Perl</application> scripts or simply a list of commands used
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| 277 | to cut and paste are just some of the methods you can use to automate
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| 278 | building BLFS packages. Detailing how and providing examples of the many
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| 279 | ways you can automate the building of packages is beyond the scope of this
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| 280 | section. This section will expose you to using file redirection and the
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| 281 | <command>yes</command> command to help provide ideas on how to automate
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| 282 | your builds.</para>
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| 283 |
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| 284 | <bridgehead renderas="sect3">File Redirection to Automate Input</bridgehead>
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| 285 |
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| 286 | <para>You will find times throughout your BLFS journey when you will come
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| 287 | across a package that has a command prompting you for information. This
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| 288 | information might be configuration details, a directory path, or a response
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| 289 | to a license agreement. This can present a challenge to automate the
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| 290 | building of that package. Occasionally, you will be prompted for different
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| 291 | information in a series of questions. One method to automate this type of
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| 292 | scenario requires putting the desired responses in a file and using
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| 293 | redirection so that the program uses the data in the file as the answers to
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| 294 | the questions.</para>
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| 295 |
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| 296 | <para>Building the <application>CUPS</application> package is a good
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| 297 | example of how redirecting a file as input to prompts can help you automate
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| 298 | the build. If you run the test suite, you are asked to respond to a series
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| 299 | of questions regarding the type of test to run and if you have any
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| 300 | auxiliary programs the test can use. You can create a file with your
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| 301 | responses, one response per line, and use a command similar to the
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| 302 | one shown below to automate running the test suite:</para>
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| 303 |
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| 304 | <screen><userinput>make check < ../cups-1.1.23-testsuite_parms</userinput></screen>
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| 305 |
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| 306 | <para>This effectively makes the test suite use the responses in the file
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[4677cbc] | 307 | as the input to the questions. Occasionally you may end up doing a bit of
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| 308 | trial and error determining the exact format of your input file for some
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| 309 | things, but once figured out and documented you can use this to automate
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| 310 | building the package.</para>
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[1080241] | 311 |
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| 312 | <bridgehead renderas="sect3">Using <command>yes</command> to Automate
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| 313 | Input</bridgehead>
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| 314 |
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| 315 | <para>Sometimes you will only need to provide one response, or provide the
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| 316 | same response to many prompts. For these instances, the
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| 317 | <command>yes</command> command works really well. The
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| 318 | <command>yes</command> command can be used to provide a response (the same
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| 319 | one) to one or more instances of questions. It can be used to simulate
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| 320 | pressing just the <keycap>Enter</keycap> key, entering the
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| 321 | <keycap>Y</keycap> key or entering a string of text. Perhaps the easiest
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| 322 | way to show its use is in an example.</para>
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| 323 |
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| 324 | <para>First, create a short <application>Bash</application> script by
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| 325 | entering the following commands:</para>
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| 326 |
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[4677cbc] | 327 | <screen><userinput>cat > blfs-yes-test1 << "EOF"
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[1080241] | 328 | <literal>#!/bin/bash
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| 329 |
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[4677cbc] | 330 | echo -n -e "\n\nPlease type something (or nothing) and press Enter ---> "
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[1080241] | 331 |
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| 332 | read A_STRING
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| 333 |
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| 334 | if test "$A_STRING" = ""; then A_STRING="Just the Enter key was pressed"
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| 335 | else A_STRING="You entered '$A_STRING'"
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| 336 | fi
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| 337 |
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[4677cbc] | 338 | echo -e "\n\n$A_STRING\n\n"</literal>
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[1080241] | 339 | EOF
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[4677cbc] | 340 | chmod 755 blfs-yes-test1</userinput></screen>
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[1080241] | 341 |
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[4677cbc] | 342 | <para>Now run the script by issuing <command>./blfs-yes-test1</command> from
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[1080241] | 343 | the command line. It will wait for a response, which can be anything (or
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| 344 | nothing) followed by the <keycap>Enter</keycap> key. After entering
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| 345 | something, the result will be echoed to the screen. Now use the
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| 346 | <command>yes</command> command to automate the entering of a
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| 347 | response:</para>
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| 348 |
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[4677cbc] | 349 | <screen><userinput>yes | ./blfs-yes-test1</userinput></screen>
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[1080241] | 350 |
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| 351 | <para>Notice that piping <command>yes</command> by itself to the script
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| 352 | results in <keycap>y</keycap> being passed to the script. Now try it with a
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| 353 | string of text:</para>
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| 354 |
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[4677cbc] | 355 | <screen><userinput>yes 'This is some text' | ./blfs-yes-test1</userinput></screen>
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[1080241] | 356 |
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| 357 | <para>The exact string was used as the response to the script. Finally,
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| 358 | try it using an empty (null) string:</para>
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| 359 |
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[4677cbc] | 360 | <screen><userinput>yes '' | ./blfs-yes-test1</userinput></screen>
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[1080241] | 361 |
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| 362 | <para>Notice this results in passing just the press of the
|
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| 363 | <keycap>Enter</keycap> key to the script. This is useful for times when the
|
---|
| 364 | default answer to the prompt is sufficient. This syntax is used in the
|
---|
| 365 | <xref linkend="net-tools-automate-example"/> instructions to accept all the
|
---|
| 366 | defaults to the many prompts during the configuration step. You may now
|
---|
| 367 | remove the test script, if desired.</para>
|
---|
| 368 |
|
---|
| 369 | <bridgehead renderas="sect3">File Redirection to Automate Output</bridgehead>
|
---|
| 370 |
|
---|
| 371 | <para>In order to automate the building of some packages, especially those
|
---|
| 372 | that require you to read a license agreement one page at a time, requires
|
---|
[6473e74] | 373 | using a method that avoids having to press a key to display each page.
|
---|
[1080241] | 374 | Redirecting the output to a file can be used in these instances to assist
|
---|
| 375 | with the automation. The previous section on this page touched on creating
|
---|
| 376 | log files of the build output. The redirection method shown there used the
|
---|
| 377 | <command>tee</command> command to redirect output to a file while also
|
---|
| 378 | displaying the output to the screen. Here, the output will only be sent to
|
---|
| 379 | a file.</para>
|
---|
| 380 |
|
---|
| 381 | <para>Again, the easiest way to demonstrate the technique is to show an
|
---|
| 382 | example. First, issue the command:</para>
|
---|
| 383 |
|
---|
| 384 | <screen><userinput>ls -l /usr/bin | more</userinput></screen>
|
---|
| 385 |
|
---|
| 386 | <para>Of course, you'll be required to view the output one page at a time
|
---|
| 387 | because the <command>more</command> filter was used. Now try the same
|
---|
| 388 | command, but this time redirect the output to a file. The special file
|
---|
| 389 | <filename>/dev/null</filename> can be used instead of the filename shown,
|
---|
| 390 | but you will have no log file to examine:</para>
|
---|
| 391 |
|
---|
| 392 | <screen><userinput>ls -l /usr/bin | more > redirect_test.log 2>&1</userinput></screen>
|
---|
| 393 |
|
---|
| 394 | <para>Notice that this time the command immediately returned to the shell
|
---|
[4677cbc] | 395 | prompt without having to page through the output. You may now remove the
|
---|
| 396 | log file.</para>
|
---|
| 397 |
|
---|
| 398 | <para>The last example will use the <command>yes</command> command in
|
---|
| 399 | combination with output redirection to bypass having to page through the
|
---|
| 400 | output and then provide a <keycap>y</keycap> to a prompt. This technique
|
---|
| 401 | could be used in instances when otherwise you would have to page through
|
---|
| 402 | the output of a file (such as a license agreement) and then answer the
|
---|
| 403 | question of <quote>do you accept the above?</quote>. For this example,
|
---|
| 404 | another short <application>Bash</application> script is required:</para>
|
---|
| 405 |
|
---|
| 406 | <screen><userinput>cat > blfs-yes-test2 << "EOF"
|
---|
[1080241] | 407 | <literal>#!/bin/bash
|
---|
| 408 |
|
---|
| 409 | ls -l /usr/bin | more
|
---|
| 410 |
|
---|
[4677cbc] | 411 | echo -n -e "\n\nDid you enjoy reading this? (y,n) "
|
---|
[1080241] | 412 |
|
---|
| 413 | read A_STRING
|
---|
| 414 |
|
---|
| 415 | if test "$A_STRING" = "y"; then A_STRING="You entered the 'y' key"
|
---|
| 416 | else A_STRING="You did NOT enter the 'y' key"
|
---|
| 417 | fi
|
---|
| 418 |
|
---|
[4677cbc] | 419 | echo -e "\n\n$A_STRING\n\n"</literal>
|
---|
[1080241] | 420 | EOF
|
---|
[4677cbc] | 421 | chmod 755 blfs-yes-test2</userinput></screen>
|
---|
[1080241] | 422 |
|
---|
| 423 | <para>This script can be used to simulate a program that requires you to
|
---|
| 424 | read a license agreement, then respond appropriately to accept the
|
---|
| 425 | agreement before the program will install anything. First, run the script
|
---|
| 426 | without any automation techniques by issuing
|
---|
[4677cbc] | 427 | <command>./blfs-yes-test2</command>.</para>
|
---|
[1080241] | 428 |
|
---|
| 429 | <para>Now issue the following command which uses two automation techniques,
|
---|
| 430 | making it suitable for use in an automated build script:</para>
|
---|
| 431 |
|
---|
[4677cbc] | 432 | <screen><userinput>yes | ./blfs-yes-test2 > blfs-yes-test2.log 2>&1</userinput></screen>
|
---|
[1080241] | 433 |
|
---|
[4677cbc] | 434 | <para>If desired, issue <command>tail blfs-yes-test2.log</command> to see
|
---|
[1080241] | 435 | the end of the paged output, and confirmation that <keycap>y</keycap> was
|
---|
| 436 | passed through to the script. Once satisfied that it works as it should,
|
---|
| 437 | you may remove the script and log file.</para>
|
---|
| 438 |
|
---|
| 439 | <para>Finally, keep in mind that there are many ways to automate and/or
|
---|
| 440 | script the build commands. There is not a single <quote>correct</quote> way
|
---|
| 441 | to do it. Your imagination is the only limit.</para>
|
---|
| 442 |
|
---|
| 443 | </sect2>
|
---|
| 444 |
|
---|
| 445 | <sect2>
|
---|
| 446 | <title>Dependencies</title>
|
---|
| 447 |
|
---|
| 448 | <para>For each package described, BLFS lists the known dependencies.
|
---|
| 449 | These are listed under several headings, whose meaning is as follows:</para>
|
---|
| 450 |
|
---|
| 451 | <itemizedlist>
|
---|
| 452 | <listitem>
|
---|
| 453 | <para><emphasis>Required</emphasis> means that the target package
|
---|
| 454 | cannot be correctly built without the dependency having first been
|
---|
| 455 | installed.</para>
|
---|
| 456 | </listitem>
|
---|
| 457 | <listitem>
|
---|
| 458 | <para><emphasis>Recommended</emphasis> means that BLFS strongly
|
---|
| 459 | suggests this package is installed first for a clean and trouble-free
|
---|
| 460 | build, that won't have issues either during the build process, or at
|
---|
[c7c1722] | 461 | run-time. The instructions in the book assume these packages are
|
---|
| 462 | installed. Some changes or workarounds may be required if these
|
---|
| 463 | packages are not installed.</para>
|
---|
[1080241] | 464 | </listitem>
|
---|
| 465 | <listitem>
|
---|
| 466 | <para><emphasis>Optional</emphasis> means that this package might be
|
---|
| 467 | installed for added functionality. Often BLFS will describe the
|
---|
| 468 | dependency to explain the added functionality that will result.</para>
|
---|
| 469 | </listitem>
|
---|
| 470 | </itemizedlist>
|
---|
| 471 |
|
---|
| 472 | </sect2>
|
---|
| 473 |
|
---|
[5d28d0d4] | 474 | <sect2 id="package_updates">
|
---|
| 475 | <title>Using the Most Current Package Sources</title>
|
---|
| 476 |
|
---|
| 477 | <para>On occasion you may run into a situation in the book when a package
|
---|
| 478 | will not build or work properly. Though the Editors attempt to ensure
|
---|
| 479 | that every package in the book builds and works properly, sometimes a
|
---|
| 480 | package has been overlooked or was not tested with this particular version
|
---|
| 481 | of BLFS.</para>
|
---|
| 482 |
|
---|
| 483 | <para>If you discover that a package will not build or work properly, you
|
---|
| 484 | should see if there is a more current version of the package. Typically
|
---|
| 485 | this means you go to the maintainer's web site and download the most current
|
---|
| 486 | tarball and attempt to build the package. If you cannot determine the
|
---|
| 487 | maintainer's web site by looking at the download URLs, use Google and query
|
---|
| 488 | the package's name. For example, in the Google search bar type:
|
---|
| 489 | 'package_name download' (omit the quotes) or something similar. Sometimes
|
---|
| 490 | typing: 'package_name home page' will result in you finding the
|
---|
| 491 | maintainer's web site.</para>
|
---|
| 492 |
|
---|
| 493 | </sect2>
|
---|
| 494 |
|
---|
[3c31062] | 495 | <sect2 id="stripping">
|
---|
| 496 | <title>Stripping One More Time</title>
|
---|
| 497 |
|
---|
[aade25df] | 498 | <para>
|
---|
[7f17762] | 499 | In LFS, stripping of debugging symbols and unneeded symbol table
|
---|
| 500 | entries was discussed a couple of times. When building BLFS packages,
|
---|
| 501 | there are generally no special instructions that discuss stripping
|
---|
| 502 | again. Stripping can be done while installing a package, or
|
---|
| 503 | afterwards.
|
---|
[70957a40] | 504 | </para>
|
---|
| 505 |
|
---|
| 506 | <bridgehead renderas="sect3" id="stripping-install">Stripping while Installing a Package</bridgehead>
|
---|
| 507 |
|
---|
| 508 | <para>
|
---|
| 509 | There are several ways to strip executables installed by a
|
---|
| 510 | package. They depend on the build system used (see below <link
|
---|
| 511 | linkend="buildsystems">the section about build systems</link>),
|
---|
| 512 | so only some
|
---|
| 513 | generalities can be listed here:
|
---|
| 514 | </para>
|
---|
| 515 |
|
---|
[7f17762] | 516 | <note>
|
---|
| 517 | <para>
|
---|
| 518 | The following methods using the feature of a building system
|
---|
| 519 | (autotools, meson, or cmake) will not strip static libraries if any
|
---|
| 520 | is installed. Fortunately there are not too many static libraries
|
---|
| 521 | in BLFS, and a static library can always be stripped safely by
|
---|
| 522 | running <command>strip --strip-unneeded</command> on it manually.
|
---|
| 523 | </para>
|
---|
| 524 | </note>
|
---|
| 525 |
|
---|
[70957a40] | 526 | <itemizedlist>
|
---|
| 527 | <listitem>
|
---|
| 528 | <para>
|
---|
| 529 | The packages using autotools usually have an
|
---|
| 530 | <parameter>install-strip</parameter> target in their generated
|
---|
| 531 | <filename>Makefile</filename> files. So installing stripped
|
---|
| 532 | executables is just a matter of using
|
---|
| 533 | <command>make install-strip</command> instead of
|
---|
| 534 | <command>make install</command>.
|
---|
| 535 | </para>
|
---|
| 536 | </listitem>
|
---|
| 537 | <listitem>
|
---|
| 538 | <para>
|
---|
| 539 | The packages using the meson build system can accept
|
---|
| 540 | <parameter>-Dstrip=true</parameter> when running
|
---|
[7f17762] | 541 | <command>meson</command>. If you've forgot to add this option
|
---|
| 542 | running the <command>meson</command>, you can also run
|
---|
| 543 | <command>meson install --strip</command> instead of
|
---|
| 544 | <command>ninja install</command>.
|
---|
[70957a40] | 545 | </para>
|
---|
| 546 | </listitem>
|
---|
| 547 | <listitem>
|
---|
| 548 | <para>
|
---|
| 549 | <command>cmake</command> generates
|
---|
| 550 | <parameter>install/strip</parameter> targets for both the
|
---|
| 551 | <parameter>Unix Makefiles</parameter> and
|
---|
| 552 | <parameter>Ninja</parameter> generators (the default is
|
---|
| 553 | <parameter>Unix Makefiles</parameter> on linux). So just run
|
---|
| 554 | <command>make install/strip</command> or
|
---|
| 555 | <command>ninja install/strip</command> instead of the
|
---|
| 556 | <command>install</command> counterparts.
|
---|
| 557 | </para>
|
---|
| 558 | </listitem>
|
---|
| 559 | <listitem>
|
---|
| 560 | <para>
|
---|
| 561 | Removing (or not generating) debug symbols can also be
|
---|
| 562 | achieved by removing the
|
---|
| 563 | <parameter>-g<something></parameter> options
|
---|
| 564 | in C/C++ calls. How to do that is very specific for each
|
---|
[7f17762] | 565 | package. And, it does not remove unneeded symbol table entries.
|
---|
| 566 | So it will not be explained in detail here. See also below
|
---|
[70957a40] | 567 | the paragraphs about optimization.
|
---|
| 568 | </para>
|
---|
| 569 | </listitem>
|
---|
| 570 | </itemizedlist>
|
---|
| 571 |
|
---|
| 572 | <bridgehead renderas="sect3" id="stripping-installed">Stripping Installed Executables</bridgehead>
|
---|
| 573 |
|
---|
| 574 | <para>
|
---|
[17fe56e1] | 575 | The <command>strip</command> utility changes files in place, which may
|
---|
| 576 | break anything using it if it is loaded in memory. Note that if a file is
|
---|
| 577 | in use but just removed from the disk (i.e. not overwritten nor
|
---|
| 578 | modified), this is not a problem since the kernel can use
|
---|
| 579 | <quote>deleted</quote> files. Look at <filename>/proc/*/maps</filename>
|
---|
| 580 | and it is likely that you'll see some <emphasis>(deleted)</emphasis>
|
---|
| 581 | entries. The <command>mv</command> just removes the destination file from
|
---|
| 582 | the directory but does not touch its content, so that it satisfies the
|
---|
| 583 | condition for the kernel to use the old (deleted) file. The script below
|
---|
[54d58907] | 584 | is just an example.
|
---|
[17fe56e1] | 585 | It should be run as the &root; user:
|
---|
[aade25df] | 586 | </para>
|
---|
[3c31062] | 587 |
|
---|
[d7bdf9f] | 588 | <screen><userinput>cat > /usr/sbin/strip-all.sh << "EOF"
|
---|
| 589 | <literal>#!/usr/bin/bash
|
---|
[17fe56e1] | 590 |
|
---|
| 591 | if [ $EUID -ne 0 ]; then
|
---|
| 592 | echo "Need to be root"
|
---|
| 593 | exit 1
|
---|
| 594 | fi
|
---|
| 595 |
|
---|
| 596 | { find /usr/lib -type f -name '*.so*' ! -name '*dbg'
|
---|
| 597 | find /usr/lib -type f -name '*.a'
|
---|
[cf799eb] | 598 | find /usr/{bin,sbin,libexec} -type f
|
---|
[17fe56e1] | 599 | } | while read file; do
|
---|
| 600 | if ! readelf -h $file >/dev/null 2>&1; then continue; fi
|
---|
[d7bdf9f] | 601 | if file $file | grep --quiet --invert-match 'not stripped'; then continue; fi
|
---|
[17fe56e1] | 602 |
|
---|
[cf799eb] | 603 | cp --preserve $file ${file}.tmp
|
---|
| 604 | strip --strip-unneeded ${file}.tmp
|
---|
| 605 | mv ${file}.tmp $file
|
---|
[17fe56e1] | 606 | done</literal>
|
---|
| 607 | EOF
|
---|
[d7bdf9f] | 608 | chmod 744 /usr/sbin/strip-all.sh</userinput></screen>
|
---|
[f3429309] | 609 |
|
---|
[aade25df] | 610 | <para>
|
---|
| 611 | If you install programs in other directories such as <filename
|
---|
| 612 | class="directory">/opt</filename> or <filename
|
---|
| 613 | class="directory">/usr/local</filename>, you may want to strip the files
|
---|
[17fe56e1] | 614 | there too. Just add other directories to scan in the compound list of
|
---|
| 615 | <command>find</command> commands between the braces.
|
---|
[aade25df] | 616 | </para>
|
---|
[3c31062] | 617 |
|
---|
[aade25df] | 618 | <para>
|
---|
| 619 | For more information on stripping, see <ulink
|
---|
[824ddcc] | 620 | url="https://www.technovelty.org/linux/stripping-shared-libraries.html"/>.
|
---|
[aade25df] | 621 | </para>
|
---|
[3c31062] | 622 |
|
---|
| 623 | </sect2>
|
---|
[70957a40] | 624 |
|
---|
[6f3460d2] | 625 | <!--
|
---|
[3c31062] | 626 | <sect2 id="libtool">
|
---|
| 627 | <title>Libtool files</title>
|
---|
| 628 |
|
---|
[aade25df] | 629 | <para>
|
---|
| 630 | One of the side effects of packages that use Autotools, including
|
---|
| 631 | libtool, is that they create many files with an .la extension. These
|
---|
| 632 | files are not needed in an LFS environment. If there are conflicts with
|
---|
| 633 | pkgconfig entries, they can actually prevent successful builds. You
|
---|
| 634 | may want to consider removing these files periodically:
|
---|
| 635 | </para>
|
---|
[3c31062] | 636 |
|
---|
[ba7bf15c] | 637 | <screen><userinput>find /lib /usr/lib -not -path "*Image*" -a -name \*.la -delete</userinput></screen>
|
---|
[16d0ef21] | 638 |
|
---|
[aade25df] | 639 | <para>
|
---|
| 640 | The above command removes all .la files with the exception of those that
|
---|
| 641 | have <quote>Image</quote> or <quote>openldap</quote> as a part of the
|
---|
| 642 | path. These .la files are used by the ImageMagick and openldap programs,
|
---|
| 643 | respectively. There may be other exceptions by packages not in BLFS.
|
---|
| 644 | </para>
|
---|
[16d0ef21] | 645 |
|
---|
[3c31062] | 646 | </sect2>
|
---|
[6f3460d2] | 647 | -->
|
---|
[ab8c10c8] | 648 | <sect2 id="buildsystems">
|
---|
| 649 | <title>Working with different build systems</title>
|
---|
| 650 |
|
---|
| 651 | <para>
|
---|
| 652 | There are now three different build systems in common use for
|
---|
| 653 | converting C or C++ source code into compiled programs or
|
---|
[367853f] | 654 | libraries and their details (particularly, finding out about available
|
---|
[ab8c10c8] | 655 | options and their default values) differ. It may be easiest to understand
|
---|
[367853f] | 656 | the issues caused by some choices (typically slow execution or
|
---|
[8fd509cb] | 657 | unexpected use of, or omission of, optimizatons) by starting with
|
---|
| 658 | the CFLAGS and CXXFLAGS environment variables. There are also some
|
---|
| 659 | programs which use rust.
|
---|
[ab8c10c8] | 660 | </para>
|
---|
| 661 |
|
---|
| 662 | <para>
|
---|
| 663 | Most LFS and BLFS builders are probably aware of the basics of CFLAGS
|
---|
| 664 | and CXXFLAGS for altering how a program is compiled. Typically, some
|
---|
[367853f] | 665 | form of optimization is used by upstream developers (-O2 or -O3),
|
---|
| 666 | sometimes with the creation of debug symbols (-g), as defaults.
|
---|
[ab8c10c8] | 667 | </para>
|
---|
| 668 |
|
---|
| 669 | <para>
|
---|
| 670 | If there are contradictory flags (e.g. multiple different -O values),
|
---|
| 671 | the <emphasis>last</emphasis> value will be used. Sometimes this means
|
---|
[367853f] | 672 | that flags specified in environment variables will be picked up before
|
---|
[ab8c10c8] | 673 | values hardcoded in the Makefile, and therefore ignored. For example,
|
---|
| 674 | where a user specifies '-O2' and that is followed by '-O3' the build will
|
---|
| 675 | use '-O3'.
|
---|
| 676 | </para>
|
---|
| 677 |
|
---|
| 678 | <para>
|
---|
| 679 | There are various other things which can be passed in CFLAGS or
|
---|
| 680 | CXXFLAGS, such as forcing compilation for a specific microarchitecture
|
---|
| 681 | (e.g. -march=amdfam10, -march=native) or specifying a specific standard
|
---|
| 682 | for C or C++ (-std=c++17 for example). But one thing which has now come
|
---|
| 683 | to light is that programmers might include debug assertions in their
|
---|
| 684 | code, expecting them to be disabled in releases by using -DNDEBUG.
|
---|
| 685 | Specifically, if <xref linkend="mesa"/> is built with these assertions
|
---|
| 686 | enabled, some activities such as loading levels of games can take
|
---|
| 687 | extremely long times, even on high-class video cards.
|
---|
| 688 | </para>
|
---|
| 689 |
|
---|
[367853f] | 690 | <bridgehead renderas="sect3" id="autotools-info">Autotools with Make</bridgehead>
|
---|
[ab8c10c8] | 691 |
|
---|
| 692 | <para>
|
---|
| 693 | This combination is often described as 'CMMI' (configure, make, make
|
---|
| 694 | install) and is used here to also cover the few packages which have a
|
---|
| 695 | configure script that is not generated by autotools.
|
---|
| 696 | </para>
|
---|
| 697 |
|
---|
| 698 | <para>
|
---|
[367853f] | 699 | Sometimes running <command>./configure --help</command> will produce
|
---|
[ab8c10c8] | 700 | useful options about switches which might be used. At other times,
|
---|
[367853f] | 701 | after looking at the output from configure you may need to look
|
---|
[ab8c10c8] | 702 | at the details of the script to find out what it was actually searching
|
---|
| 703 | for.
|
---|
| 704 | </para>
|
---|
| 705 |
|
---|
| 706 | <para>
|
---|
| 707 | Many configure scripts will pick up any CFLAGS or CXXFLAGS from the
|
---|
| 708 | environment, but CMMI packages vary about how these will be mixed with
|
---|
| 709 | any flags which would otherwise be used (<emphasis>variously</emphasis>:
|
---|
| 710 | ignored, used to replace the programmer's suggestion, used before the
|
---|
[367853f] | 711 | programmer's suggestion, or used after the programmer's suggestion).
|
---|
[ab8c10c8] | 712 | </para>
|
---|
| 713 |
|
---|
| 714 | <para>
|
---|
| 715 | In most CMMI packages, running 'make' will list each command and run
|
---|
| 716 | it, interspersed with any warnings. But some packages try to be 'silent'
|
---|
| 717 | and only show which file they are compiling or linking instead of showing
|
---|
| 718 | the command line. If you need to inspect the command, either because of
|
---|
| 719 | an error, or just to see what options and flags are being used, adding
|
---|
| 720 | 'V=1' to the make invocation may help.
|
---|
| 721 | </para>
|
---|
| 722 |
|
---|
[367853f] | 723 | <bridgehead renderas="sect3" id="cmake-info">CMake</bridgehead>
|
---|
[ab8c10c8] | 724 |
|
---|
| 725 | <para>
|
---|
| 726 | CMake works in a very different way, and it has two backends which can
|
---|
| 727 | be used on BLFS: 'make' and 'ninja'. The default backend is make, but
|
---|
| 728 | ninja can be faster on large packages with multiple processors. To
|
---|
[c0e4599e] | 729 | use ninja, specify '-G Ninja' in the cmake command. However, there are
|
---|
| 730 | some packages which create fatal errors in their ninja files but build
|
---|
| 731 | successfully using the default of Unix Makefiles.
|
---|
[ab8c10c8] | 732 | </para>
|
---|
| 733 |
|
---|
| 734 | <para>
|
---|
| 735 | The hardest part of using CMake is knowing what options you might wish
|
---|
| 736 | to specify. The only way to get a list of what the package knows about
|
---|
| 737 | is to run <command>cmake -LAH</command> and look at the output for that
|
---|
| 738 | default configuration.
|
---|
| 739 | </para>
|
---|
| 740 |
|
---|
| 741 | <para>
|
---|
| 742 | Perhaps the most-important thing about CMake is that it has a variety
|
---|
| 743 | of CMAKE_BUILD_TYPE values, and these affect the flags. The default
|
---|
| 744 | is that this is not set and no flags are generated. Any CFLAGS or
|
---|
[367853f] | 745 | CXXFLAGS in the environment will be used. If the programmer has coded
|
---|
[ab8c10c8] | 746 | any debug assertions, those will be enabled unless -DNDEBUG is used.
|
---|
| 747 | The following CMAKE_BUILD_TYPE values will generate the flags shown,
|
---|
| 748 | and these will come <emphasis>after</emphasis> any flags in the
|
---|
| 749 | environment and therefore take precedence.
|
---|
| 750 | </para>
|
---|
| 751 |
|
---|
[c6c57f7] | 752 | <informaltable align="center">
|
---|
| 753 | <tgroup cols="2">
|
---|
| 754 | <colspec colnum="1" align="center"/>
|
---|
| 755 | <colspec colnum="2" align="center"/>
|
---|
| 756 | <thead>
|
---|
| 757 | <row><entry>Value</entry><entry>Flags</entry></row>
|
---|
| 758 | </thead>
|
---|
| 759 | <tbody>
|
---|
| 760 | <row>
|
---|
| 761 | <entry>Debug</entry><entry><option>-g</option></entry>
|
---|
| 762 | </row>
|
---|
| 763 | <row>
|
---|
| 764 | <entry>Release</entry><entry><option>-O3 -DNDEBUG</option></entry>
|
---|
| 765 | </row>
|
---|
| 766 | <row>
|
---|
| 767 | <entry>RelWithDebInfo</entry><entry><option>-O2 -g -DNDEBUG</option></entry>
|
---|
| 768 | </row>
|
---|
| 769 | <row>
|
---|
| 770 | <entry>MinSizeRel</entry><entry><option>-Os -DNDEBUG</option></entry>
|
---|
| 771 | </row>
|
---|
| 772 | </tbody>
|
---|
| 773 | </tgroup>
|
---|
| 774 | </informaltable>
|
---|
[ab8c10c8] | 775 |
|
---|
| 776 | <para>
|
---|
| 777 | CMake tries to produce quiet builds. To see the details of the commands
|
---|
[c6c57f7] | 778 | which are being run, use <command>make VERBOSE=1</command> or
|
---|
| 779 | <command>ninja -v</command>.
|
---|
[ab8c10c8] | 780 | </para>
|
---|
[02743f9c] | 781 |
|
---|
| 782 | <para>
|
---|
| 783 | By default, CMake treats file installation differently from the other
|
---|
| 784 | build systems: if a file already exists and is not newer than a file
|
---|
| 785 | that would overwrite it, then the file is not installed. This may be
|
---|
| 786 | a problem if a user wants to record which file belongs to a package,
|
---|
| 787 | either using <envar>LD_PRELOAD</envar>, or by listing files newer
|
---|
| 788 | than a timestamp. The default can be changed by setting the variable
|
---|
| 789 | <envar>CMAKE_INSTALL_ALWAYS</envar> to 1 in the
|
---|
| 790 | <emphasis>environment</emphasis>, for example by
|
---|
| 791 | <command>export</command>'ing it.
|
---|
| 792 | </para>
|
---|
[ab8c10c8] | 793 |
|
---|
[367853f] | 794 | <bridgehead renderas="sect3" id="meson-info">Meson</bridgehead>
|
---|
[ab8c10c8] | 795 |
|
---|
| 796 | <para>
|
---|
| 797 | Meson has some similarities to CMake, but many differences. To get
|
---|
[f66b2ee] | 798 | details of the defines that you may wish to change you can look at
|
---|
| 799 | <filename>meson_options.txt</filename> which is usually in the
|
---|
| 800 | top-level directory.
|
---|
[ab8c10c8] | 801 | </para>
|
---|
| 802 |
|
---|
| 803 | <para>
|
---|
[f66b2ee] | 804 | If you have already configured the package by running
|
---|
| 805 | <command>meson</command> and now wish to change one or more settings,
|
---|
| 806 | you can either remove the build directory, recreate it, and use the
|
---|
| 807 | altered options, or within the build directory run <command>meson
|
---|
| 808 | configure</command>, e.g. to set an option:
|
---|
[ab8c10c8] | 809 | </para>
|
---|
| 810 |
|
---|
[f66b2ee] | 811 | <screen><userinput>meson configure -D<some_option>=true</userinput></screen>
|
---|
[ab8c10c8] | 812 |
|
---|
| 813 | <para>
|
---|
[f66b2ee] | 814 | If you do that, the file <filename>meson-private/cmd_line.txt</filename>
|
---|
| 815 | will show the <emphasis>last</emphasis> commands which were used.
|
---|
[ab8c10c8] | 816 | </para>
|
---|
| 817 |
|
---|
| 818 | <para>
|
---|
| 819 | Meson provides the following buildtype values, and the flags they enable
|
---|
| 820 | come <emphasis>after</emphasis> any flags supplied in the environment and
|
---|
| 821 | therefore take precedence.
|
---|
| 822 | </para>
|
---|
| 823 |
|
---|
| 824 | <itemizedlist>
|
---|
| 825 | <listitem>
|
---|
| 826 | <para>plain : no added flags. This is for distributors to supply their
|
---|
| 827 | own CLFAGS, CXXFLAGS and LDFLAGS. There is no obvious reason to use
|
---|
| 828 | this in BLFS.</para>
|
---|
| 829 | </listitem>
|
---|
| 830 | <listitem>
|
---|
[65877d86] | 831 | <para>debug : '-g' - this is the default if nothing is specified
|
---|
[8554ad2] | 832 | in either <filename>meson.build</filename> or the command line.
|
---|
[c98fc5b] | 833 | However it results large and slow binaries, so we should override
|
---|
| 834 | it in BLFS.</para>
|
---|
[ab8c10c8] | 835 | </listitem>
|
---|
| 836 | <listitem>
|
---|
[65877d86] | 837 | <para>debugoptimized : '-O2 -g' : this is the default specified in
|
---|
| 838 | <filename>meson.build</filename> of some packages.</para>
|
---|
[ab8c10c8] | 839 | </listitem>
|
---|
| 840 | <listitem>
|
---|
[8fd509cb] | 841 | <para>release : '-O3 -DNDEBUG' (but occasionally a package will force
|
---|
| 842 | -O2 here)</para>
|
---|
[ab8c10c8] | 843 | </listitem>
|
---|
| 844 | </itemizedlist>
|
---|
| 845 |
|
---|
| 846 | <para>
|
---|
[367853f] | 847 | Although the 'release' buildtype is described as enabling -DNDEBUG, and all
|
---|
[ab8c10c8] | 848 | CMake Release builds pass that, it has so far only been observed (in
|
---|
| 849 | verbose builds) for <xref linkend="mesa"/>. That suggests that it might
|
---|
| 850 | only be used when there are debug assertions present.
|
---|
| 851 | </para>
|
---|
| 852 |
|
---|
| 853 | <para>
|
---|
| 854 | The -DNDEBUG flag can also be provided by passing
|
---|
| 855 | <command>-Db_ndebug=true</command>.
|
---|
| 856 | </para>
|
---|
| 857 |
|
---|
| 858 | <para>
|
---|
| 859 | To see the details of the commands which are being run in a package using
|
---|
[367853f] | 860 | meson, use 'ninja -v'.
|
---|
[ab8c10c8] | 861 | </para>
|
---|
| 862 |
|
---|
[8fd509cb] | 863 | <bridgehead renderas="sect3" id="rust-info">Rustc and Cargo</bridgehead>
|
---|
| 864 |
|
---|
| 865 | <para>
|
---|
| 866 | Most released rustc programs are provided as crates (source tarballs)
|
---|
| 867 | which will query a server to check current versions of dependencies
|
---|
| 868 | and then download them as necessary. These packages are built using
|
---|
| 869 | <command>cargo --release</command>. In theory, you can manipulate the
|
---|
| 870 | RUSTFLAGS to change the optimize-level (default is 3, like -O3, e.g.
|
---|
| 871 | <literal>-Copt-level=3</literal>) or to force it to build for the
|
---|
| 872 | machine it is being compiled on, using
|
---|
| 873 | <literal>-Ctarget-cpu=native</literal> but in practice this seems to
|
---|
| 874 | make no significant difference.
|
---|
| 875 | </para>
|
---|
| 876 |
|
---|
| 877 | <para>
|
---|
| 878 | If you find an interesting rustc program which is only provided as
|
---|
| 879 | unpackaged source, you should at least specify
|
---|
| 880 | <literal>RUSTFLAGS=-Copt-level=2</literal> otherwise it will do an
|
---|
| 881 | unoptimized compile with debug info and run <emphasis>much</emphasis>
|
---|
| 882 | slower.
|
---|
| 883 | </para>
|
---|
| 884 |
|
---|
[5ce1bdb] | 885 | <para>
|
---|
| 886 | The rust developers seem to assume that everyone will compile on a
|
---|
| 887 | machine dedicated to producing builds, so by default all CPUs are used.
|
---|
| 888 | This can often be worked around, either by exporting
|
---|
| 889 | CARGO_BUILD_JOBS=<N> or passing --jobs <N> to cargo. For
|
---|
| 890 | compiling rustc itself, specifying --jobs <N> on invocations of
|
---|
| 891 | x.py (together with the <envar>CARGO_BUILD_JOBS</envar> environment
|
---|
| 892 | variable, which looks like a "belt and braces" approach but seems to be
|
---|
| 893 | necessary) mostly works. The exception is running the tests when building
|
---|
| 894 | rustc, some of them will nevertheless use all online CPUs, at least as of
|
---|
| 895 | rustc-1.42.0.
|
---|
| 896 | </para>
|
---|
| 897 |
|
---|
[8fd509cb] | 898 | </sect2>
|
---|
| 899 |
|
---|
| 900 | <sect2 id="optimizations">
|
---|
| 901 | <title>Optimizing the build</title>
|
---|
| 902 |
|
---|
| 903 | <para>
|
---|
| 904 | Many people will prefer to optimize compiles as they see fit, by providing
|
---|
| 905 | CFLAGS or CXXFLAGS. For an introduction to the options available with gcc
|
---|
| 906 | and g++ see <ulink
|
---|
| 907 | url="https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html"/> and <ulink
|
---|
| 908 | url="https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html"/>
|
---|
| 909 | and <command>info gcc</command>.
|
---|
| 910 |
|
---|
| 911 | </para>
|
---|
| 912 |
|
---|
| 913 | <para>
|
---|
| 914 | Some packages default to '-O2 -g', others to '-O3 -g', and if CFLAGS or
|
---|
| 915 | CXXFLAGS are supplied they might be added to the package's defaults,
|
---|
| 916 | replace the package's defaults, or even be ignored. There are details
|
---|
| 917 | on some desktop packages which were mostly current in April 2019 at
|
---|
[c9aa980] | 918 | <ulink url="https://www.linuxfromscratch.org/~ken/tuning/"/> - in
|
---|
[8fd509cb] | 919 | particular, README.txt, tuning-1-packages-and-notes.txt, and
|
---|
| 920 | tuning-notes-2B.txt. The particular thing to remember is that if you
|
---|
[7c93be03] | 921 | want to try some of the more interesting flags you may need to force
|
---|
[8fd509cb] | 922 | verbose builds to confirm what is being used.
|
---|
| 923 | </para>
|
---|
| 924 |
|
---|
| 925 | <para>
|
---|
| 926 | Clearly, if you are optimizing your own program you can spend time to
|
---|
| 927 | profile it and perhaps recode some of it if it is too slow. But for
|
---|
| 928 | building a whole system that approach is impractical. In general,
|
---|
| 929 | -O3 usually produces faster programs than -O2. Specifying
|
---|
| 930 | -march=native is also beneficial, but means that you cannot move the
|
---|
| 931 | binaries to an incompatible machine - this can also apply to newer
|
---|
| 932 | machines, not just to older machines. For example programs compiled for
|
---|
| 933 | 'amdfam10' run on old Phenoms, Kaveris, and Ryzens : but programs
|
---|
| 934 | compiled for a Kaveri will not run on a Ryzen because certain op-codes
|
---|
| 935 | are not present. Similarly, if you build for a Haswell not everything
|
---|
| 936 | will run on a SandyBridge.
|
---|
| 937 | </para>
|
---|
| 938 |
|
---|
| 939 | <para>
|
---|
| 940 | There are also various other options which some people claim are
|
---|
| 941 | beneficial. At worst, you get to recompile and test, and then
|
---|
| 942 | discover that in your usage the options do not provide a benefit.
|
---|
| 943 | </para>
|
---|
| 944 |
|
---|
| 945 | <para>
|
---|
| 946 | If building Perl or Python modules, or Qt packages which use qmake,
|
---|
| 947 | in general the CFLAGS and CXXFLAGS used are those which were used by
|
---|
| 948 | those 'parent' packages.
|
---|
| 949 | </para>
|
---|
| 950 |
|
---|
| 951 | </sect2>
|
---|
| 952 |
|
---|
| 953 | <sect2 id="hardening">
|
---|
| 954 | <title>Options for hardening the build</title>
|
---|
| 955 |
|
---|
| 956 | <para>
|
---|
| 957 | Even on desktop systems, there are still a lot of exploitable
|
---|
| 958 | vulnerabilities. For many of these, the attack comes via javascript
|
---|
[52249aa] | 959 | in a browser. Often, a series of vulnerabilities are used to gain
|
---|
[8fd509cb] | 960 | access to data (or sometimes to pwn, i.e. own, the machine and
|
---|
| 961 | install rootkits). Most commercial distros will apply various
|
---|
| 962 | hardening measures.
|
---|
| 963 | </para>
|
---|
| 964 |
|
---|
| 965 | <para>
|
---|
[5a95524] | 966 | In the past, there was Hardened LFS where gcc (a much older version)
|
---|
| 967 | was forced to use hardening (with options to turn some of it off on a
|
---|
[8d2373d8] | 968 | per-package basis). The current LFS and BLFS books are carrying
|
---|
[5a95524] | 969 | forward a part of its spirit by enabling PIE
|
---|
| 970 | (<option>-fPIE -pie</option>) and SSP
|
---|
| 971 | (<option>-fstack-protector-strong</option>) as the defaults
|
---|
| 972 | for GCC and clang. What is being covered here is different - first
|
---|
| 973 | you have to make sure that the package is indeed using your added
|
---|
| 974 | flags and not over-riding them.
|
---|
[8fd509cb] | 975 | </para>
|
---|
| 976 |
|
---|
| 977 | <para>
|
---|
[5a95524] | 978 | For hardening options which are reasonably cheap, there is some
|
---|
| 979 | discussion in the 'tuning' link above (occasionally, one or more
|
---|
| 980 | of these options might be inappropriate for a package). These
|
---|
| 981 | options are <option>-D_FORTIFY_SOURCE=2</option> and
|
---|
| 982 | (for C++) <option>-D_GLIBCXX_ASSERTIONS</option>. On modern
|
---|
| 983 | machines these should only have a little impact on how fast things
|
---|
| 984 | run, and often they will not be noticeable.
|
---|
[8fd509cb] | 985 | </para>
|
---|
| 986 |
|
---|
| 987 | <para>
|
---|
| 988 | The main distros use much more, such as RELRO (Relocation Read Only)
|
---|
[5a95524] | 989 | and perhaps <option>-fstack-clash-protection</option>. You may also
|
---|
| 990 | encounter the so-called <quote>userspace retpoline</quote>
|
---|
| 991 | (<option>-mindirect-branch=thunk</option> etc.) which
|
---|
[8fd509cb] | 992 | is the equivalent of the spectre mitigations applied to the linux
|
---|
[640313a] | 993 | kernel in late 2018. The kernel mitigations caused a lot of complaints
|
---|
[8fd509cb] | 994 | about lost performance, if you have a production server you might wish
|
---|
| 995 | to consider testing that, along with the other available options, to
|
---|
| 996 | see if performance is still sufficient.
|
---|
| 997 | </para>
|
---|
| 998 |
|
---|
| 999 | <para>
|
---|
| 1000 | Whilst gcc has many hardening options, clang/LLVM's strengths lie
|
---|
| 1001 | elsewhere. Some options which gcc provides are said to be less effective
|
---|
[bf5fb94] | 1002 | in clang/LLVM.
|
---|
[8fd509cb] | 1003 | </para>
|
---|
| 1004 |
|
---|
[ab8c10c8] | 1005 | </sect2>
|
---|
| 1006 |
|
---|
[1080241] | 1007 | </sect1>
|
---|