mirror of
https://github.com/Zeckmathederg/glfs.git
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2f6d8ec100
command lines like this: linux /boot/vmlinuz-5.2.11-lfs-SVN-20190902 root=UUID=47a81d89-8788-4ec4-99dd-0f3a0943e96b resume=LABEL=MYSWAP ro initrd /boot/initrd.img-5.2.11-lfs-1 git-svn-id: svn://svn.linuxfromscratch.org/BLFS/trunk/BOOK@22107 af4574ff-66df-0310-9fd7-8a98e5e911e0
446 lines
13 KiB
XML
446 lines
13 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % general-entities SYSTEM "../../general.ent">
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%general-entities;
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]>
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<sect1 id="initramfs">
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<?dbhtml filename="initramfs.html"?>
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<sect1info>
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<othername>$LastChangedBy$</othername>
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<date>$Date$</date>
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</sect1info>
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<title>About initramfs</title>
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<para>The only purpose of an initramfs is to mount the root filesystem. The
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initramfs is a complete set of directories that you would find on a normal
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root filesystem. It is bundled into a single cpio archive and compressed
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with one of several compression algorithms.</para>
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<para>At boot time, the boot loader loads the kernel and the initramfs image
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into memory and starts the kernel. The kernel checks for the presence of the
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initramfs and, if found, mounts it as / and runs /init. The init program is
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typically a shell script. Note that the boot process takes longer, possibly
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significantly longer, if an initramfs is used.</para>
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<para>For most distributions, kernel modules are the biggest reason to have an
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initramfs. In a general distribution, there are many unknowns such as file
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system types and disk layouts. In a way, this is the opposite of LFS where
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the system capabilities and layout are known and a custom kernel is normally
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built. In this situation, an initramfs is rarely needed.</para>
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<para>There are only four primary reasons to have an initramfs in the LFS
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environment: loading the rootfs from a network, loading it from an LVM
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logical volume, having an encrypted rootfs where a password is required, or
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for the convenience of specifying the rootfs as a LABEL or UUID. Anything
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else usually means that the kernel was not configured properly.</para>
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<sect2 id="initramfs-build">
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<title>Building an initramfs</title>
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<para>If you do decide to build an initramfs, the following scripts
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will provide a basis to do it. The scripts will allow specifying a
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rootfs via partition UUID or partition LABEL or a rootfs on an
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LVM logical volume. They do not support an encrypted root file system
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or mounting the rootfs over a network card. For a more complete
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capability see <ulink url="http://www.linuxfromscratch.org/hints/read.html">
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the LFS Hints</ulink> or <ulink url="http://fedoraproject.org/wiki/Dracut">
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dracut</ulink>.</para>
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<para>To install these scripts, run the following commands as the
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<systemitem class="username">root</systemitem> user:</para>
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<screen role="root"><userinput>cat > /sbin/mkinitramfs << "EOF"
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<literal>#!/bin/bash
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# This file based in part on the mkinitramfs script for the LFS LiveCD
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# written by Alexander E. Patrakov and Jeremy Huntwork.
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copy()
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{
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local file
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if [ "$2" == "lib" ]; then
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file=$(PATH=/lib:/usr/lib type -p $1)
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else
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file=$(type -p $1)
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fi
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if [ -n $file ] ; then
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cp $file $WDIR/$2
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else
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echo "Missing required file: $1 for directory $2"
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rm -rf $WDIR
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exit 1
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fi
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}
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if [ -z $1 ] ; then
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INITRAMFS_FILE=initrd.img-no-kmods
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else
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KERNEL_VERSION=$1
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INITRAMFS_FILE=initrd.img-$KERNEL_VERSION
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fi
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if [ -n "$KERNEL_VERSION" ] && [ ! -d "/lib/modules/$1" ] ; then
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echo "No modules directory named $1"
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exit 1
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fi
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printf "Creating $INITRAMFS_FILE... "
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binfiles="sh cat cp dd killall ls mkdir mknod mount "
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binfiles="$binfiles umount sed sleep ln rm uname"
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binfiles="$binfiles readlink basename"
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# Systemd installs udevadm in /bin. Other udev implementations have it in /sbin
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if [ -x /bin/udevadm ] ; then binfiles="$binfiles udevadm"; fi
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sbinfiles="modprobe blkid switch_root"
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#Optional files and locations
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for f in mdadm mdmon udevd udevadm; do
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if [ -x /sbin/$f ] ; then sbinfiles="$sbinfiles $f"; fi
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done
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unsorted=$(mktemp /tmp/unsorted.XXXXXXXXXX)
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DATADIR=/usr/share/mkinitramfs
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INITIN=init.in
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# Create a temporary working directory
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WDIR=$(mktemp -d /tmp/initrd-work.XXXXXXXXXX)
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# Create base directory structure
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mkdir -p $WDIR/{bin,dev,lib/firmware,run,sbin,sys,proc,usr}
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mkdir -p $WDIR/etc/{modprobe.d,udev/rules.d}
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touch $WDIR/etc/modprobe.d/modprobe.conf
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ln -s lib $WDIR/lib64
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ln -s ../bin $WDIR/usr/bin
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# Create necessary device nodes
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mknod -m 640 $WDIR/dev/console c 5 1
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mknod -m 664 $WDIR/dev/null c 1 3
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# Install the udev configuration files
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if [ -f /etc/udev/udev.conf ]; then
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cp /etc/udev/udev.conf $WDIR/etc/udev/udev.conf
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fi
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for file in $(find /etc/udev/rules.d/ -type f) ; do
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cp $file $WDIR/etc/udev/rules.d
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done
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# Install any firmware present
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cp -a /lib/firmware $WDIR/lib
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# Copy the RAID configuration file if present
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if [ -f /etc/mdadm.conf ] ; then
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cp /etc/mdadm.conf $WDIR/etc
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fi
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# Install the init file
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install -m0755 $DATADIR/$INITIN $WDIR/init
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if [ -n "$KERNEL_VERSION" ] ; then
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if [ -x /bin/kmod ] ; then
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binfiles="$binfiles kmod"
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else
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binfiles="$binfiles lsmod"
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sbinfiles="$sbinfiles insmod"
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fi
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fi
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# Install basic binaries
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for f in $binfiles ; do
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if [ -e /bin/$f ]; then d="/bin"; else d="/usr/bin"; fi
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ldd $d/$f | sed "s/\t//" | cut -d " " -f1 >> $unsorted
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copy $d/$f bin
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done
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# Add lvm if present
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if [ -x /sbin/lvm ] ; then sbinfiles="$sbinfiles lvm dmsetup"; fi
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for f in $sbinfiles ; do
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ldd /sbin/$f | sed "s/\t//" | cut -d " " -f1 >> $unsorted
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copy $f sbin
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done
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# Add udevd libraries if not in /sbin
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if [ -x /lib/udev/udevd ] ; then
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ldd /lib/udev/udevd | sed "s/\t//" | cut -d " " -f1 >> $unsorted
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elif [ -x /lib/systemd/systemd-udevd ] ; then
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ldd /lib/systemd/systemd-udevd | sed "s/\t//" | cut -d " " -f1 >> $unsorted
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fi
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# Add module symlinks if appropriate
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if [ -n "$KERNEL_VERSION" ] && [ -x /bin/kmod ] ; then
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ln -s kmod $WDIR/bin/lsmod
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ln -s kmod $WDIR/bin/insmod
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fi
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# Add lvm symlinks if appropriate
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# Also copy the lvm.conf file
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if [ -x /sbin/lvm ] ; then
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ln -s lvm $WDIR/sbin/lvchange
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ln -s lvm $WDIR/sbin/lvrename
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ln -s lvm $WDIR/sbin/lvextend
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ln -s lvm $WDIR/sbin/lvcreate
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ln -s lvm $WDIR/sbin/lvdisplay
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ln -s lvm $WDIR/sbin/lvscan
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ln -s lvm $WDIR/sbin/pvchange
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ln -s lvm $WDIR/sbin/pvck
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ln -s lvm $WDIR/sbin/pvcreate
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ln -s lvm $WDIR/sbin/pvdisplay
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ln -s lvm $WDIR/sbin/pvscan
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ln -s lvm $WDIR/sbin/vgchange
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ln -s lvm $WDIR/sbin/vgcreate
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ln -s lvm $WDIR/sbin/vgscan
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ln -s lvm $WDIR/sbin/vgrename
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ln -s lvm $WDIR/sbin/vgck
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# Conf file(s)
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cp -a /etc/lvm $WDIR/etc
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fi
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# Install libraries
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sort $unsorted | uniq | while read library ; do
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if [ "$library" == "linux-vdso.so.1" ] ||
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[ "$library" == "linux-gate.so.1" ]; then
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continue
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fi
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copy $library lib
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done
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if [ -d /lib/udev ]; then
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cp -a /lib/udev $WDIR/lib
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fi
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if [ -d /lib/systemd ]; then
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cp -a /lib/systemd $WDIR/lib
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fi
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if [ -d /lib/elogind ]; then
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cp -a /lib/elogind $WDIR/lib
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fi
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# Install the kernel modules if requested
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if [ -n "$KERNEL_VERSION" ]; then
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find \
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/lib/modules/$KERNEL_VERSION/kernel/{crypto,fs,lib} \
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/lib/modules/$KERNEL_VERSION/kernel/drivers/{block,ata,md,firewire} \
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/lib/modules/$KERNEL_VERSION/kernel/drivers/{scsi,message,pcmcia,virtio} \
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/lib/modules/$KERNEL_VERSION/kernel/drivers/usb/{host,storage} \
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-type f 2> /dev/null | cpio --make-directories -p --quiet $WDIR
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cp /lib/modules/$KERNEL_VERSION/modules.{builtin,order} \
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$WDIR/lib/modules/$KERNEL_VERSION
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depmod -b $WDIR $KERNEL_VERSION
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fi
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( cd $WDIR ; find . | cpio -o -H newc --quiet | gzip -9 ) > $INITRAMFS_FILE
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# Remove the temporary directory and file
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rm -rf $WDIR $unsorted
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printf "done.\n"
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</literal>
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EOF
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chmod 0755 /sbin/mkinitramfs</userinput></screen>
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<screen role="root"><userinput>mkdir -p /usr/share/mkinitramfs &&
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cat > /usr/share/mkinitramfs/init.in << "EOF"
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<literal>#!/bin/sh
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PATH=/bin:/usr/bin:/sbin:/usr/sbin
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export PATH
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problem()
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{
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printf "Encountered a problem!\n\nDropping you to a shell.\n\n"
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sh
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}
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no_device()
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{
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printf "The device %s, which is supposed to contain the\n" $1
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printf "root file system, does not exist.\n"
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printf "Please fix this problem and exit this shell.\n\n"
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}
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no_mount()
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{
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printf "Could not mount device %s\n" $1
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printf "Sleeping forever. Please reboot and fix the kernel command line.\n\n"
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printf "Maybe the device is formatted with an unsupported file system?\n\n"
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printf "Or maybe filesystem type autodetection went wrong, in which case\n"
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printf "you should add the rootfstype=... parameter to the kernel command line.\n\n"
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printf "Available partitions:\n"
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}
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do_mount_root()
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{
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mkdir /.root
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[ -n "$rootflags" ] && rootflags="$rootflags,"
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rootflags="$rootflags$ro"
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case "$root" in
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/dev/* ) device=$root ;;
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UUID=* ) eval $root; device="/dev/disk/by-uuid/$UUID" ;;
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LABEL=*) eval $root; device="/dev/disk/by-label/$LABEL" ;;
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"" ) echo "No root device specified." ; problem ;;
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esac
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while [ ! -b "$device" ] ; do
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no_device $device
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problem
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done
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if ! mount -n -t "$rootfstype" -o "$rootflags" "$device" /.root ; then
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no_mount $device
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cat /proc/partitions
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while true ; do sleep 10000 ; done
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else
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echo "Successfully mounted device $root"
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fi
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}
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do_try_resume()
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{
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case "$resume" in
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UUID=* ) eval $resume; resume="/dev/disk/by-uuid/$UUID" ;;
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LABEL=*) eval $resume; resume="/dev/disk/by-label/$LABEL" ;;
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esac
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if $noresume || ! [ -b "$resume" ]; then return; fi
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ls -lH "$resume" | ( read x x x x maj min x
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echo -n ${maj%,}:$min > /sys/power/resume )
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}
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init=/sbin/init
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root=
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rootdelay=
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rootfstype=auto
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ro="ro"
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rootflags=
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device=
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resume=
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noresume=false
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mount -n -t devtmpfs devtmpfs /dev
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mount -n -t proc proc /proc
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mount -n -t sysfs sysfs /sys
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mount -n -t tmpfs tmpfs /run
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read -r cmdline < /proc/cmdline
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for param in $cmdline ; do
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case $param in
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init=* ) init=${param#init=} ;;
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root=* ) root=${param#root=} ;;
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rootdelay=* ) rootdelay=${param#rootdelay=} ;;
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rootfstype=*) rootfstype=${param#rootfstype=} ;;
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rootflags=* ) rootflags=${param#rootflags=} ;;
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resume=* ) resume=${param#resume=} ;;
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noresume ) noresume=true ;;
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ro ) ro="ro" ;;
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rw ) ro="rw" ;;
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esac
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done
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# udevd location depends on version
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if [ -x /sbin/udevd ]; then
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UDEVD=/sbin/udevd
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elif [ -x /lib/udev/udevd ]; then
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UDEVD=/lib/udev/udevd
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elif [ -x /lib/systemd/systemd-udevd ]; then
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UDEVD=/lib/systemd/systemd-udevd
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else
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echo "Cannot find udevd nor systemd-udevd"
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problem
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fi
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${UDEVD} --daemon --resolve-names=never
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udevadm trigger
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udevadm settle
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if [ -f /etc/mdadm.conf ] ; then mdadm -As ; fi
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if [ -x /sbin/vgchange ] ; then /sbin/vgchange -a y > /dev/null ; fi
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if [ -n "$rootdelay" ] ; then sleep "$rootdelay" ; fi
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do_try_resume # This function will not return if resuming from disk
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do_mount_root
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killall -w ${UDEVD##*/}
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exec switch_root /.root "$init" "$@"
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</literal>
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EOF</userinput></screen>
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</sect2>
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<sect2 id="initramfs-install">
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<title>Using an initramfs</title>
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<bridgehead renderas="sect3">Required Runtime Dependency</bridgehead>
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<para role="required">
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<xref role="runtime" linkend="cpio"/>
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</para>
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<para condition="html" role="usernotes">User Notes:
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<ulink url="&blfs-wiki;/initramfs"/>
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</para>
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<para>To build an initramfs, run the following as the <systemitem
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class="username">root</systemitem> user:</para>
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<screen role="nodump"><userinput>mkinitramfs [KERNEL VERSION]</userinput></screen>
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<para>The optional argument is the directory where the appropriate kernel
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modules are located. This must be a subdirectory of <filename
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class='directory'> /lib/modules</filename>. If no modules are specified,
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then the initramfs is named <emphasis>initrd.img-no-kmods</emphasis>. If a
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kernel version is specified, the initrd is named
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<emphasis>initrd.img-$KERNEL_VERSION</emphasis> and is only appropriate for
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the specific kernel specified. The output file will be placed in the
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current directory.</para>
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<para>After generating the initrd, copy it to the <filename
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class='directory'>/boot</filename> directory.</para>
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<para>Now edit <filename>/boot/grub/grub.cfg</filename> and add a new
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menuentry. Below are several examples.</para>
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<screen role="nodump"><userinput># Generic initramfs and root fs identified by UUID
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menuentry "LFS Dev (LFS-7.0-Feb14) initrd, Linux 3.0.4"
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{
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linux /vmlinuz-3.0.4-lfs-20120214 root=UUID=54b934a9-302d-415e-ac11-4988408eb0a8 ro
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initrd /initrd.img-no-kmods
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}</userinput></screen>
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<screen role="nodump"><userinput># Generic initramfs and root fs on LVM partition
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menuentry "LFS Dev (LFS-7.0-Feb18) initrd lvm, Linux 3.0.4"
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{
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linux /vmlinuz-3.0.4-lfs-20120218 root=/dev/mapper/myroot ro
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initrd /initrd.img-no-kmods
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}</userinput></screen>
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<screen role="nodump"><userinput># Specific initramfs and root fs identified by LABEL
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menuentry "LFS Dev (LFS-7.1-Feb20) initrd label, Linux 3.2.6"
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{
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linux /vmlinuz-3.2.6-lfs71-120220 root=LABEL=lfs71 ro
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initrd /initrd.img-3.2.6-lfs71-120220
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}</userinput></screen>
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<para>Finally, reboot the system and select the desired system.</para>
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</sect2>
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</sect1>
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