source: chapter07/createfiles.xml@ fcc02767

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Last change on this file since fcc02767 was fcc02767, checked in by Bruce Dubbs <bdubbs@…>, 18 months ago

Initial commit of alternative cross LFS

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../general.ent">
5 %general-entities;
6]>
7
8<sect1 id="ch-tools-createfiles">
9 <?dbhtml filename="createfiles.html"?>
10
11 <title>Creating Essential Files and Symlinks</title>
12
13 <indexterm zone="ch-tools-createfiles">
14 <primary sortas="e-/etc/passwd">/etc/passwd</primary>
15 </indexterm>
16
17 <indexterm zone="ch-tools-createfiles">
18 <primary sortas="e-/etc/group">/etc/group</primary>
19 </indexterm>
20
21 <indexterm zone="ch-tools-createfiles">
22 <primary sortas="e-/var/run/utmp">/var/run/utmp</primary>
23 </indexterm>
24
25 <indexterm zone="ch-tools-createfiles">
26 <primary sortas="e-/var/log/btmp">/var/log/btmp</primary>
27 </indexterm>
28
29 <indexterm zone="ch-tools-createfiles">
30 <primary sortas="e-/var/log/lastlog">/var/log/lastlog</primary>
31 </indexterm>
32
33 <indexterm zone="ch-tools-createfiles">
34 <primary sortas="e-/var/log/wtmp">/var/log/wtmp</primary>
35 </indexterm>
36
37 <para>Historically, Linux maintains a list of the mounted file systems in the
38 file <filename>/etc/mtab</filename>. Modern kernels maintain this list
39 internally and exposes it to the user via the <filename
40 class="directory">/proc</filename> filesystem. To satisfy utilities that
41 expect the presence of <filename>/etc/mtab</filename>, create the following
42 symbolic link:</para>
43
44<screen><userinput>ln -sv /proc/self/mounts /etc/mtab</userinput></screen>
45
46 <para>In order for user <systemitem class="username">root</systemitem> to be
47 able to login and for the name <quote>root</quote> to be recognized, there
48 must be relevant entries in the <filename>/etc/passwd</filename> and
49 <filename>/etc/group</filename> files.</para>
50
51 <para>Create the <filename>/etc/passwd</filename> file by running the following
52 command:</para>
53
54<screen revision="sysv"><userinput>cat &gt; /etc/passwd &lt;&lt; "EOF"
55<literal>root:x:0:0:root:/root:/bin/bash
56bin:x:1:1:bin:/dev/null:/bin/false
57daemon:x:6:6:Daemon User:/dev/null:/bin/false
58messagebus:x:18:18:D-Bus Message Daemon User:/var/run/dbus:/bin/false
59nobody:x:99:99:Unprivileged User:/dev/null:/bin/false</literal>
60EOF</userinput></screen>
61
62<screen revision="systemd"><userinput>cat &gt; /etc/passwd &lt;&lt; "EOF"
63<literal>root:x:0:0:root:/root:/bin/bash
64bin:x:1:1:bin:/dev/null:/bin/false
65daemon:x:6:6:Daemon User:/dev/null:/bin/false
66messagebus:x:18:18:D-Bus Message Daemon User:/var/run/dbus:/bin/false
67systemd-bus-proxy:x:72:72:systemd Bus Proxy:/:/bin/false
68systemd-journal-gateway:x:73:73:systemd Journal Gateway:/:/bin/false
69systemd-journal-remote:x:74:74:systemd Journal Remote:/:/bin/false
70systemd-journal-upload:x:75:75:systemd Journal Upload:/:/bin/false
71systemd-network:x:76:76:systemd Network Management:/:/bin/false
72systemd-resolve:x:77:77:systemd Resolver:/:/bin/false
73systemd-timesync:x:78:78:systemd Time Synchronization:/:/bin/false
74systemd-coredump:x:79:79:systemd Core Dumper:/:/bin/false
75nobody:x:99:99:Unprivileged User:/dev/null:/bin/false</literal>
76EOF</userinput></screen>
77
78 <para>The actual password for <systemitem class="username">root</systemitem>
79 (the <quote>x</quote> used here is just a placeholder) will be set later.</para>
80
81 <para>Create the <filename>/etc/group</filename> file by running the following
82 command:</para>
83
84<screen revision="sysv"><userinput>cat &gt; /etc/group &lt;&lt; "EOF"
85<literal>root:x:0:
86bin:x:1:daemon
87sys:x:2:
88kmem:x:3:
89tape:x:4:
90tty:x:5:
91daemon:x:6:
92floppy:x:7:
93disk:x:8:
94lp:x:9:
95dialout:x:10:
96audio:x:11:
97video:x:12:
98utmp:x:13:
99usb:x:14:
100cdrom:x:15:
101adm:x:16:
102messagebus:x:18:
103input:x:24:
104mail:x:34:
105kvm:x:61:
106wheel:x:97:
107nogroup:x:99:
108users:x:999:</literal>
109EOF</userinput></screen>
110
111<screen revision="systemd"><userinput>cat &gt; /etc/group &lt;&lt; "EOF"
112<literal>root:x:0:
113bin:x:1:daemon
114sys:x:2:
115kmem:x:3:
116tape:x:4:
117tty:x:5:
118daemon:x:6:
119floppy:x:7:
120disk:x:8:
121lp:x:9:
122dialout:x:10:
123audio:x:11:
124video:x:12:
125utmp:x:13:
126usb:x:14:
127cdrom:x:15:
128adm:x:16:
129messagebus:x:18:
130systemd-journal:x:23:
131input:x:24:
132mail:x:34:
133kvm:x:61:
134systemd-bus-proxy:x:72:
135systemd-journal-gateway:x:73:
136systemd-journal-remote:x:74:
137systemd-journal-upload:x:75:
138systemd-network:x:76:
139systemd-resolve:x:77:
140systemd-timesync:x:78:
141systemd-coredump:x:79:
142wheel:x:97:
143nogroup:x:99:
144users:x:999:</literal>
145EOF</userinput></screen>
146
147 <para>The created groups are not part of any standard&mdash;they are groups
148 decided on in part by the requirements of the Udev configuration in the next
149 chapter, and in part by common convention employed by a number of existing
150 Linux distributions. In addition, some test suites rely on specific users
151 or groups. The Linux Standard Base (LSB, available at <ulink
152 url="http://www.linuxbase.org"/>) recommends only that, besides the group
153 <systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0,
154 a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be
155 present. All other group names and GIDs can be chosen freely by the system
156 administrator since well-written programs do not depend on GID numbers, but
157 rather use the group's name.</para>
158
159 <para>Some tests in <xref linkend="chapter-building-system"/> need a regular
160 user. We add this user here and delete this account at the end of that
161 chapter.</para>
162
163<screen><userinput>echo "tester:x:$(ls -n $(tty) | cut -d" " -f3):101::/home/tester:/bin/bash" &gt;&gt; /etc/passwd
164echo "tester:x:101:" &gt;&gt; /etc/group
165install -o tester -d /home/tester</userinput></screen>
166
167 <para>To remove the <quote>I have no name!</quote> prompt, start a new
168 shell. Since the
169 <filename>/etc/passwd</filename> and <filename>/etc/group</filename>
170 files have been created, user name and group name resolution will now
171 work:</para>
172
173<screen role="nodump"><userinput>exec /bin/bash --login +h</userinput></screen>
174
175 <para>Note the use of the <parameter>+h</parameter> directive. This tells
176 <command>bash</command> not to use its internal path hashing. Without this
177 directive, <command>bash</command> would remember the paths to binaries it has
178 executed. To ensure the use of the newly compiled binaries as soon as they are
179 installed, the <parameter>+h</parameter> directive will be used for the duration
180 of this chapter.</para>
181
182 <para>The <command>login</command>, <command>agetty</command>, and
183 <command>init</command> programs (and others) use a number of log
184 files to record information such as who was logged into the system and
185 when. However, these programs will not write to the log files if they
186 do not already exist. Initialize the log files and give them
187 proper permissions:</para>
188
189<screen><userinput>touch /var/log/{btmp,lastlog,faillog,wtmp}
190chgrp -v utmp /var/log/lastlog
191chmod -v 664 /var/log/lastlog
192chmod -v 600 /var/log/btmp</userinput></screen>
193
194 <para>The <filename>/var/log/wtmp</filename> file records all logins and
195 logouts. The <filename>/var/log/lastlog</filename> file records when each
196 user last logged in. The <filename>/var/log/faillog</filename> file records
197 failed login attempts. The <filename>/var/log/btmp</filename> file records
198 the bad login attempts.</para>
199
200 <note><para>The <filename>/run/utmp</filename> file records the users that
201 are currently logged in. This file is created dynamically in the boot
202 scripts.</para></note>
203
204</sect1>
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