[a32a241] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[5632009] | 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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[a42ba00] | 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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[5632009] | 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="initramfs">
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| 9 | <?dbhtml filename="initramfs.html"?>
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| 10 |
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| 11 | <sect1info>
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| 12 | <othername>$LastChangedBy$</othername>
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| 13 | <date>$Date$</date>
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| 14 | </sect1info>
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| 15 |
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| 16 | <title>About initramfs</title>
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| 17 |
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| 18 | <para>The only purpose of an initramfs is to mount the root filesystem. The
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| 19 | initramfs is a complete set of directories that you would find on a normal
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| 20 | root filesystem. It is bundled into a single cpio archive and compressed
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| 21 | with one of several compression algorithms.</para>
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| 22 |
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| 23 | <para>At boot time, the boot loader loads the kernel and the initramfs image
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| 24 | into memory and starts the kernel. The kernel checks for the presence of the
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| 25 | initramfs and, if found, mounts it as / and runs /init. The init program is
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| 26 | typically a shell script. Note that the boot process takes longer, possibly
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[64cb61a] | 27 | significantly longer, if an initramfs is used.</para>
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[5632009] | 28 |
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| 29 | <para>For most distributions, kernel modules are the biggest reason to have an
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| 30 | initramfs. In a general distribution, there are many unknowns such as file
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| 31 | system types and disk layouts. In a way, this is the opposite of LFS where
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| 32 | the system capabilities and layout are known and a custom kernel is normally
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| 33 | built. In this situation, an initramfs is rarely needed.</para>
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| 34 |
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| 35 | <para>There are only four primary reasons to have an initramfs in the LFS
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| 36 | environment: loading the rootfs from a network, loading it from an LVM
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| 37 | logical volume, having an encrypted rootfs where a password is required, or
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| 38 | for the convenience of specifying the rootfs as a LABEL or UUID. Anything
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| 39 | else usually means that the kernel was not configured properly.</para>
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| 40 |
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| 41 | <sect2 id="initramfs-build">
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| 42 | <title>Building an initramfs</title>
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| 43 |
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| 44 | <para>If you do decide to build an initramfs, the following scripts
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| 45 | will provide a basis to do it. The scripts will allow specifying a
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| 46 | rootfs via partition UUID or partition LABEL or a rootfs on an
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| 47 | LVM logical volume. They do not support an encrypted root file system
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| 48 | or mounting the rootfs over a network card. For a more complete
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| 49 | capability see <ulink url="http://www.linuxfromscratch.org/hints/read.html">
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| 50 | the LFS Hints</ulink> or <ulink url="http://fedoraproject.org/wiki/Dracut">
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| 51 | dracut</ulink>.</para>
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| 52 |
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| 53 | <para>To install these scripts, run the following commands as the
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| 54 | <systemitem class="username">root</systemitem> user:</para>
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| 55 |
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| 56 | <screen role="root"><userinput>cat > /sbin/mkinitramfs << "EOF"
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| 57 | #!/bin/bash
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| 58 | # This file based in part on the mkinitrafms script for the LFS LiveCD
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| 59 | # written by Alexander E. Patrakov and Jeremy Huntwork.
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| 60 |
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| 61 | copy()
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| 62 | {
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| 63 | local file
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| 64 |
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| 65 | if [ "$2" == "lib" ]; then
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| 66 | file=$(PATH=/lib:/usr/lib type -p $1)
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| 67 | else
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| 68 | file=$(type -p $1)
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| 69 | fi
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| 70 |
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| 71 | if [ -n $file ] ; then
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| 72 | cp $file $WDIR/$2
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| 73 | else
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| 74 | echo "Missing required file: $1 for directory $2"
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| 75 | rm -rf $WDIR
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| 76 | exit 1
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| 77 | fi
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| 78 | }
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| 79 |
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| 80 | if [ -z $1 ] ; then
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| 81 | INITRAMFS_FILE=initrd.img-no-kmods
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| 82 | else
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| 83 | KERNEL_VERSION=$1
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| 84 | INITRAMFS_FILE=initrd.img-$KERNEL_VERSION
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| 85 | fi
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| 86 |
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| 87 | if [ -n "$KERNEL_VERSION" ] && [ ! -d "/lib/modules/$1" ] ; then
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| 88 | echo "No modules directory named $1"
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| 89 | exit 1
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| 90 | fi
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| 91 |
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| 92 | printf "Creating $INITRAMFS_FILE... "
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| 93 |
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[90c6607] | 94 | binfiles="sh cat cp dd killall ls mkdir mknod mount "
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[5632009] | 95 | binfiles="$binfiles umount sed sleep ln rm uname"
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| 96 |
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[90c6607] | 97 | sbinfiles="udevadm modprobe blkid switch_root"
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| 98 |
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[8253f9fc] | 99 | #Optional files and locations
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| 100 | for f in mdadm udevd; do
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| 101 | if [ -x /sbin/$f ] ; then sbinfiles="$sbinfiles $f"; fi
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| 102 | done
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[5632009] | 103 |
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| 104 | unsorted=$(mktemp /tmp/unsorted.XXXXXXXXXX)
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| 105 |
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| 106 | DATADIR=/usr/share/mkinitramfs
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| 107 | INITIN=init.in
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| 108 |
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| 109 | # Create a temporrary working directory
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| 110 | WDIR=$(mktemp -d /tmp/initrd-work.XXXXXXXXXX)
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| 111 |
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| 112 | # Create base directory structure
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| 113 | mkdir -p $WDIR/{bin,dev,lib/firmware,run,sbin,sys,proc}
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| 114 | mkdir -p $WDIR/etc/{modprobe.d,udev/rules.d}
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| 115 | touch $WDIR/etc/modprobe.d/modprobe.conf
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| 116 | ln -s lib $WDIR/lib64
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| 117 |
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| 118 | # Create necessary device nodes
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| 119 | mknod -m 640 $WDIR/dev/console c 5 1
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| 120 | mknod -m 664 $WDIR/dev/null c 1 3
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| 121 |
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| 122 | # Install the udev configuration files
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| 123 | cp /etc/udev/udev.conf $WDIR/etc/udev/udev.conf
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| 124 |
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| 125 | for file in $(find /etc/udev/rules.d/ -type f) ; do
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| 126 | cp $file $WDIR/etc/udev/rules.d
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| 127 | done
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| 128 |
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[a32a241] | 129 | # Install any firmware present
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| 130 | cp -a /lib/firmware $WDIR/lib
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| 131 |
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| 132 | # Copy the RAID configureation file if present
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[5632009] | 133 | if [ -f /etc/mdadm.conf ] ; then
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| 134 | cp /etc/mdadm.conf $WDIR/etc
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| 135 | fi
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| 136 |
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| 137 | # Install the init file
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| 138 | install -m0755 $DATADIR/$INITIN $WDIR/init
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| 139 |
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[ea8a884] | 140 | if [ -n "$KERNEL_VERSION" ] ; then
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| 141 | if [ -x /bin/kmod ] ; then
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| 142 | binfiles="$binfiles kmod"
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| 143 | else
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| 144 | binfiles="$binfiles lsmod"
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[64cb61a] | 145 | sbinfiles="$sbinfiles insmod"
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[ea8a884] | 146 | fi
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| 147 | fi
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| 148 |
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[5632009] | 149 | # Install basic binaries
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| 150 | for f in $binfiles ; do
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| 151 | ldd /bin/$f | sed "s/\t//" | cut -d " " -f1 >> $unsorted
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| 152 | copy $f bin
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| 153 | done
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| 154 |
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| 155 | # Add lvm if present
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| 156 | if [ -x /sbin/lvm ] ; then sbinfiles="$sbinfiles lvm"; fi
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| 157 |
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| 158 | for f in $sbinfiles ; do
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| 159 | ldd /sbin/$f | sed "s/\t//" | cut -d " " -f1 >> $unsorted
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| 160 | copy $f sbin
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| 161 | done
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| 162 |
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[8253f9fc] | 163 | # Add udevd libraries if not in /sbin
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| 164 | if [ -x /lib/udev/udevd ] ; then
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| 165 | ldd /lib/udev/udevd | sed "s/\t//" | cut -d " " -f1 >> $unsorted
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| 166 | fi
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| 167 |
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[ea8a884] | 168 | # Add module symlinks if appropriate
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| 169 | if [ -n "$KERNEL_VERSION" ] && [ -x /bin/kmod ] ; then
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| 170 | ln -s kmod $WDIR/bin/lsmod
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| 171 | ln -s kmod $WDIR/bin/insmod
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| 172 | fi
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| 173 |
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[5632009] | 174 | # Add lvm symlinks if appropriate
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| 175 | if [ -x /sbin/lvm ] ; then
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| 176 | ln -s lvm $WDIR/sbin/lvchange
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[8253f9fc] | 177 | ln -s lvm $WDIR/sbin/lvrename
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| 178 | ln -s lvm $WDIR/sbin/lvextend
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[5632009] | 179 | ln -s lvm $WDIR/sbin/lvcreate
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| 180 | ln -s lvm $WDIR/sbin/lvdisplay
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| 181 | ln -s lvm $WDIR/sbin/lvscan
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| 182 |
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| 183 | ln -s lvm $WDIR/sbin/pvchange
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| 184 | ln -s lvm $WDIR/sbin/pvck
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| 185 | ln -s lvm $WDIR/sbin/pvcreate
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| 186 | ln -s lvm $WDIR/sbin/pvdisplay
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| 187 | ln -s lvm $WDIR/sbin/pvscan
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| 188 |
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[068c8df] | 189 | ln -s lvm $WDIR/sbin/vgchange
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[5632009] | 190 | ln -s lvm $WDIR/sbin/vgcreate
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| 191 | ln -s lvm $WDIR/sbin/vgscan
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| 192 | ln -s lvm $WDIR/sbin/vgrename
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| 193 | ln -s lvm $WDIR/sbin/vgck
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| 194 | fi
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| 195 |
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| 196 | # Install libraries
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[8253f9fc] | 197 | sort $unsorted | uniq | while read library ; do
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| 198 | if [ "$library" == "linux-vdso.so.1" ] ||
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| 199 | [ "$library" == "linux-gate.so.1" ]; then
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[5632009] | 200 | continue
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| 201 | fi
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| 202 |
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| 203 | copy $library lib
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| 204 | done
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| 205 |
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| 206 | cp -a /lib/udev $WDIR/lib
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| 207 |
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| 208 | # Install the kernel modules if requested
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| 209 | if [ -n "$KERNEL_VERSION" ]; then
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| 210 | find \
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| 211 | /lib/modules/$KERNEL_VERSION/kernel/{crypto,fs,lib} \
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| 212 | /lib/modules/$KERNEL_VERSION/kernel/drivers/{block,ata,md,firewire} \
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| 213 | /lib/modules/$KERNEL_VERSION/kernel/drivers/{scsi,message,pcmcia,virtio} \
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| 214 | /lib/modules/$KERNEL_VERSION/kernel/drivers/usb/{host,storage} \
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| 215 | -type f 2> /dev/null | cpio --make-directories -p --quiet $WDIR
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| 216 |
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[8253f9fc] | 217 | cp /lib/modules/$KERNEL_VERSION/modules.{builtin,order} \
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| 218 | $WDIR/lib/modules/$KERNEL_VERSION
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| 219 |
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[5632009] | 220 | depmod -b $WDIR $KERNEL_VERSION
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| 221 | fi
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| 222 |
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| 223 | ( cd $WDIR ; find . | cpio -o -H newc --quiet | gzip -9 ) > $INITRAMFS_FILE
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| 224 |
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| 225 | # Remove the temporary directory and file
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| 226 | rm -rf $WDIR $unsorted
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| 227 | printf "done.\n"
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| 228 |
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| 229 | EOF</userinput></screen>
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| 230 |
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| 231 | <screen role="root"><userinput>mkdir -p /usr/share/mkinitramfs &&
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| 232 | cat > /usr/share/mkinitramfs/init.in << "EOF"
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| 233 | #!/bin/sh
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| 234 |
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| 235 | PATH=/bin:/usr/bin:/sbin:/usr/sbin
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| 236 | export PATH
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| 237 |
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| 238 | problem()
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| 239 | {
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| 240 | printf "Encountered a problem!\n\nDropping you to a shell.\n\n"
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| 241 | sh
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| 242 | }
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| 243 |
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| 244 | no_device()
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| 245 | {
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| 246 | printf "The device %s, which is supposed to contain the\n" $1
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| 247 | printf "root file system, does not exist.\n"
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| 248 | printf "Please fix this problem and exit this shell.\n\n"
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| 249 | }
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| 250 |
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| 251 | no_mount()
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| 252 | {
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| 253 | printf "Could not mount device %s\n" $1
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| 254 | printf "Sleeping forever. Please reboot and fix the kernel command line.\n\n"
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| 255 | printf "Maybe the device is formatted with an unsupported file system?\n\n"
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| 256 | printf "Or maybe filesystem type autodetection went wrong, in which case\n"
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| 257 | printf "you should add the rootfstype=... parameter to the kernel command line.\n\n"
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| 258 | printf "Available partitions:\n"
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| 259 | }
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| 260 |
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| 261 | do_mount_root()
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| 262 | {
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| 263 | mkdir /.root
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| 264 | [ -n "$rootflags" ] && rootflags="$rootflags,"
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| 265 | rootflags="$rootflags$ro"
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| 266 |
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| 267 | case "$root" in
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| 268 | /dev/* ) device=$root ;;
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| 269 | UUID=* ) eval $root; device="/dev/disk/by-uuid/$UUID" ;;
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[4a20b84] | 270 | LABEL=*) eval $root; device="/dev/disk/by-label/$LABEL" ;;
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[5632009] | 271 | "" ) echo "No root device specified." ; problem ;;
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| 272 | esac
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| 273 |
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| 274 | while [ ! -b "$device" ] ; do
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| 275 | no_device $device
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| 276 | problem
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| 277 | done
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| 278 |
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| 279 | if ! mount -n -t "$rootfstype" -o "$rootflags" "$device" /.root ; then
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| 280 | no_mount $device
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| 281 | cat /proc/partitions
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| 282 | while true ; do sleep 10000 ; done
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| 283 | else
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| 284 | echo "Successfully mounted device $root"
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| 285 | fi
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| 286 | }
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| 287 |
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| 288 | init=/sbin/init
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| 289 | root=
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| 290 | rootdelay=
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| 291 | rootfstype=auto
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| 292 | ro="ro"
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| 293 | rootflags=
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| 294 | device=
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| 295 |
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| 296 | mount -n -t devtmpfs devtmpfs /dev
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[a32a241] | 297 | mount -n -t proc proc /proc
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| 298 | mount -n -t sysfs sysfs /sys
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| 299 | mount -n -t tmpfs tmpfs /run
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[5632009] | 300 |
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| 301 | read -r cmdline < /proc/cmdline
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| 302 |
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| 303 | for param in $cmdline ; do
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| 304 | case $param in
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| 305 | init=* ) init=${param#init=} ;;
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| 306 | root=* ) root=${param#root=} ;;
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| 307 | rootdelay=* ) rootdelay=${param#rootdelay=} ;;
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| 308 | rootfstype=*) rootfstype=${param#rootfstype=} ;;
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| 309 | rootflags=* ) rootflags=${param#rootflags=} ;;
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| 310 | ro ) ro="ro" ;;
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| 311 | rw ) ro="rw" ;;
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| 312 | esac
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| 313 | done
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| 314 |
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[8253f9fc] | 315 | # udevd location depends on version
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| 316 | if [ -x /sbin/udevd ]; then
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| 317 | UDEV_PATH=/sbin
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| 318 | else
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| 319 | UDEV_PATH=/lib/udev
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| 320 | fi
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| 321 |
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| 322 | ${UDEV_PATH}/udevd --daemon --resolve-names=never
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[5632009] | 323 | udevadm trigger
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| 324 | udevadm settle
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| 325 |
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| 326 | if [ -f /etc/mdadm.conf ] ; then mdadm -As ; fi
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| 327 | if [ -x /sbin/vgchange ] ; then /sbin/vgchange -a y > /dev/null ; fi
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| 328 | if [ -n "$rootdelay" ] ; then sleep "$rootdelay" ; fi
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| 329 |
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| 330 | do_mount_root
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| 331 |
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[8253f9fc] | 332 | killall -w ${UDEV_PATH}/udevd
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[5632009] | 333 |
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| 334 | exec switch_root /.root "$init" "$@"
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| 335 |
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| 336 | EOF</userinput></screen>
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| 337 |
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| 338 | </sect2>
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| 339 |
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| 340 | <sect2 id="initramfs-install">
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| 341 | <title>Using an initramfs</title>
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| 342 |
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[ea8a884] | 343 | <bridgehead renderas="sect3">Required Runtime Dependency</bridgehead>
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| 344 |
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| 345 | <para role="required">
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| 346 | <xref linkend="cpio"/>
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| 347 | </para>
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| 348 |
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| 349 | <para condition="html" role="usernotes">User Notes:
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| 350 | <ulink url="&blfs-wiki;/initramfs"/>
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| 351 | </para>
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| 352 |
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| 353 |
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[5632009] | 354 | <para>To build an initramfs, run the following as the <systemitem
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| 355 | class="username">root</systemitem> user:</para>
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| 356 |
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| 357 | <screen><userinput>mkinitramfs [KERNEL VERSION]</userinput></screen>
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| 358 |
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| 359 | <para>The optional argument is the directory where the appropriate kernel
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| 360 | modules are located. This must be a subdirectory of <filename
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| 361 | class='directory'> /lib/modules</filename>. If no modules are specified,
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| 362 | then the initramfs is named <emphasis>initrd.img-no-kmods</emphasis>. If a
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| 363 | kernel version is specified, the initrd is named
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| 364 | <emphasis>initrd.img-$KERNEL_VERSION</emphasis> and is only appropriate for
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| 365 | the specific kernel specified. The output file will be placed in the
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| 366 | current directory.</para>
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| 367 |
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| 368 | <para>After generating the initrd, copy it to the <filename
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| 369 | class='directory'>/boot</filename> directory.</para>
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| 370 |
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| 371 | <para>Now edit <filename>/boot/grub/grub.cfg</filename> and add a new
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| 372 | menuentry. Below are several examples.</para>
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| 373 |
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| 374 | <screen><userinput># Generic initramfs and root fs identified by UUID
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| 375 | menuentry "LFS Dev (LFS-7.0-Feb14) initrd, Linux 3.0.4"
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| 376 | {
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| 377 | linux /vmlinuz-3.0.4-lfs-20120214 root=UUID=54b934a9-302d-415e-ac11-4988408eb0a8 ro
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| 378 | initrd /initrd.img-no-kmods
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| 379 | }</userinput></screen>
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| 380 |
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| 381 | <screen><userinput># Generic initramfs and root fs on LVM partition
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| 382 | menuentry "LFS Dev (LFS-7.0-Feb18) initrd lvm, Linux 3.0.4"
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| 383 | {
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| 384 | linux /vmlinuz-3.0.4-lfs-20120218 root=/dev/mapper/myroot ro
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| 385 | initrd /initrd.img-no-kmods
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| 386 | }</userinput></screen>
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| 387 |
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| 388 | <screen><userinput># Specific initramfs and root fs identified by LABEL
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| 389 | menuentry "LFS Dev (LFS-7.1-Feb20) initrd label, Linux 3.2.6"
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| 390 | {
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| 391 | linux /vmlinuz-3.2.6-lfs71-120220 root=LABEL=lfs71 ro
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| 392 | initrd /initrd.img-3.2.6-lfs71-120220
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| 393 | }</userinput></screen>
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| 394 |
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| 395 | <para>Finally, reboot the system and select the desired system.</para>
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| 396 |
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| 397 | </sect2>
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| 398 |
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| 399 | </sect1>
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