Install Arch Linux from existing Linux

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Revision as of 17:00, 16 February 2013 by Buergi (talk | contribs) (readd Direct Bootstrapping, @Danielwallace pls don't remove a section without correcting the references (1. method etc.), direct bootstrapping is the quickest and most memory efficient way and absolute crucial for installation on remote hosts)
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zh-CN:Install from Existing Linux zh-TW:Install from Existing Linux This guide is intended for anybody who wants to install Arch Linux from any other running Linux -- be it off a LiveCD or a pre-existing install of a different distro.

This is useful for:

  • remotely installing Archlinux (e.g. a (virtual) root server)
  • creating a new linux distribution or LiveCD based on Archlinux
  • creating an Archlinux chroot environments
  • rootfs-over-NFS for diskless machines

This guide requires that the existing host system be able to execute the new target Arch Linux architecture programs. In the case of an x86_64 host, it is possible to use i686-pacman to build a 32-bit chroot environment. See Arch64 Install bundled 32bit system. However it is not so easy to build a 64-bit environment when the host only supports running 32-bit programs.

Note: If you are already using Arch, instead of following this guide, just install arch-install-scripts from the official repositories and follow the Installation Guide

This guide provides additional steps to the Installation Guide. The steps of that guide must still be followed as needed.

Prepare the system

Follow the Installation Guide steps, until you have your partitions, keyboard and internet connection ready.

Setup the environment for pacman

You need to create an environment where pacman and the arch install scripts can run on your current linux distro. (If you choose the Method 2, only pacman is necessary)

There are in principle two different methods to prepare that environment: either by installing pacman natively (Method 4 below) on your linux distro or by setting up a chroot environment. The latter way will generally be easier and is discussed next:

There are two possible ways of using the chroot method:

  • Using chroot as an installation environment: The prepared Archlinux chroot environment will be used temporarily to set up the actual Archlinux installation using the arch-install-scripts. This is a bit more work and takes longer but once you set up the installation system you can quickly install several Archlinux systems. However, if you want to set up only a single Archlinux this might be overkill. You are actually setting up the system twice, have a lot more network traffic and especially need a lot more RAM and disk space, mostly due to the quite big iso image.
  • Installing Archlinux directly/Direct Bootstrapping: Thanks to tokland's arch-bootstrap script this method is effectively a one-liner and very fast. After that one line of code your Archlinux base system is installed to disk. However, if setting up multiple copies of Archlinux, this method requires the re-downloading of the base packages every time, so is slower.

The best advice is probably to use Direct bootstrapping to set up only a small number of systems. If you set up many Archlinux systems the chroot install environment or even the native pacman installation might suit you better.

Method 1: Chroot into LiveCD-image

It is possible to mount the root image of the latest Archlinux installation media and then chroot into it. This method has the advantage of providing you with a working Arch Linux installation right within your host system without the need to prepare it by installing specific packages.

Note: Before proceeding, make sure the latest version of squashfs-tools is installed on the host system. Otherwise you will get errors like: FATAL ERROR aborting: uncompress_inode_table: failed to read block.
  • Mount the Live CD image:
# mount -o loop archlinux-{date}-dual.iso /mnt
  • The root image exists in squashfs format on the Live CD. The squashfs format is not editable as such. Hence, we unsquash the root image and then mount it.

To unsquash the x86_64 (or i686 respectively) root image, run

# unsquashfs -d /squashfs-root /mnt/arch/x86_64/root-image.fs.sfs
  • Now you can unmount and remove the iso image
# umount /mnt
# rm archlinux-{date}-dual.iso
  • Now you can loop mount the root image
# mount -o loop /squashfs-root/root-image.fs /arch
  • Before chrooting to it, we need to set up some mount points.
# mount -t proc none /arch/proc
# mount -t sysfs none /arch/sys
# mount -o bind /dev /arch/dev
# mount -o bind /dev/pts /arch/dev/pts # important for pacman (for signature check)
  • Now everything is prepared to chroot into your newly installed Arch environment
# chroot /arch bash

This chroot is able to execute the arch install scripts. The destination partitions should be mounted under the /mnt directory from this chroot.

Method 2: Direct bootstrapping Archlinux

This method will install a basic Archlinux system directly onto your previously prepared root file system mounted as /mnt. This is known as bootstrapping and is definitely the quickest way to install a single Archlinux system from a foreign distribution. Moreover, it is less disk consuming as method 1 as it does not require to download the whole Archlinux installation image. Therefore bootstrapping is the method of choice for installing Archlinux on a remote host, such as a virtual root server using some arbitrary GNU/Linux-based rescue environment.

As described in the Installation Guide we assume your disk which should become your root device is mountet at /mnt. At first grab tokland's arch-bootstrap script, c.f. Archbootstrap,

# cd /tmp
# wget
# chmod +x

This script will bootstrap a basic archlinux system, i.e., it will download the linux kernel, pacman basic tools like bash and all needed dependencies and unpack them to the given directory, in this case /mnt.

If you are wanting to install a 32-bit system:

# ./ -a i686 -r "" /mnt/

Or a 64-bit system:

# ./ -a x86_64 -r "" /mnt/

The bootstrapping will take 2-5 minutes depending on the speed of your system.

If the architecture of the foreign distribution is not the same as the one of the newly bootstrapped system you might have to change the architecture in /etc/pacman.conf.

If your bootstrapped system is 32-bit system:

Architecture = i686

Or for a 64-bit system:

Architecture = x86_64

Before chrooting into the newly created system we need to set up some mount points. This is essential for the installation of a bootloader later on, c.f. Change Root.

# mount -t proc none /mnt/proc
# mount -t sysfs none /mnt/sys
# mount -o bind /dev /mnt/dev
# mount -o bind /dev/pts /mnt/dev/pts # important for pacman (for signature check)

Now everything is prepared to chroot into your newly installed Arch environment

# chroot /mnt bash

Before you can use pacman you have to initialize its keyring as explained below, in #Fix the Pacman Signature Keyring.

From here on proceed with Installation Guide#Install the base system, but remember, you are already working in your final system, thus no need for pacstrap, simply use pacman. So the next command you are most likely to execute will be

 # pacman -S base # and evtl. also base-devel

Credit goes to Arnau Sanchez alias tokland, the author of the arch-bootstrap script.

Method 3: Bootstrapping the arch installation scripts

Contrary to the other methods, this method is one-step only; you only have to execute the script below and thats it.

This method can be considered an hybrid between Method 1 and Method 2. It provides a chroot enviroment from where to execute the arch install scripts (similar to Method 1), by using a bootstrapping script (similar to Method 2).

The script below is going to create a directory called archinstall-pkg and download the required packages there. Then, is going to extract them into the archinstall-chroot directory. Finally, is going to prepare mount points, configure pacman and enter into a chroot.

Note: This is only an enviroment to execute the arch install scripts: this is not your final installation.

This chroot is able to execute the arch install scripts. The destination partitions should be mounted under the /mnt directory from this chroot. After that, continue with the next step, which is #Fix the Pacman Signature Keyring.

CHROOT_DIR=archinstall-chroot Must Change First, or you might ruin your /etc/
# This script is inspired on the archbootstrap script.

PACKAGES=(acl attr bzip2 curl expat glibc gpgme libarchive libassuan libgpg-error libssh2 openssl pacman xz zlib pacman-mirrorlist coreutils bash grep gawk file tar ncurses readline libcap util-linux pcre arch-install-scripts)
# Change the mirror as necessary
# You can set the ARCH variable to i686 or x86_64
ARCH=`uname -m`
mkdir -p "$DIR"
mkdir -p "$CHROOT_DIR"
# Create a list with urls for the arch packages
for REPO in core community extra; do  
        wget -q -O- "$MIRROR/$REPO/os/$ARCH/" |sed  -n "s|.*href=\"\\([^\"]*\\).*|$MIRROR\\/$REPO\\/os\\/$ARCH\\/\\1|p"|grep -v 'sig$'|uniq >> $LIST  
# Download and extract each package.
for PACKAGE in ${PACKAGES[*]}; do
        URL=`grep "$PACKAGE-[0-9]" $LIST|head -n1`
        FILE=`echo $URL|sed 's/.*\/\([^\/][^\/]*\)$/\1/'`
        wget "$URL" -c -O "$DIR/$FILE" 
        xz -dc "$DIR/$FILE" | tar x -k -C "$CHROOT_DIR"
# Create mount points
mkdir -p "$CHROOT_DIR/dev" "$CHROOT_DIR/proc" "$CHROOT_DIR/sys" "$CHROOT_DIR/mnt"
mount -t proc proc "$CHROOT_DIR/proc/"
mount -t sysfs sys "$CHROOT_DIR/sys/"
mount -o bind /dev "$CHROOT_DIR/dev/"
mkdir -p "$CHROOT_DIR/dev/pts"
mount -t devpts pts "$CHROOT_DIR/dev/pts/"

# Hash for empty password  Created by doing: openssl passwd -1 -salt ihlrowCo and entering an empty password (just press enter)
echo 'root:$1$ihlrowCo$sF0HjA9E8up9DYs258uDQ0:10063:0:99999:7:::' > "$CHROOT_DIR/etc/shadow"
echo "root:x:0:0:root:/root:/bin/bash" > "$CHROOT_DIR/etc/passwd" 
touch "$CHROOT_DIR/etc/group"
echo "myhost" > "$CHROOT_DIR/etc/hostname"
test -e "$CHROOT_DIR/etc/mtab" || echo "rootfs / rootfs rw 0 0" > "$CHROOT_DIR/etc/mtab"
[ -f "/etc/resolv.conf" ] && cp "/etc/resolv.conf" "$CHROOT_DIR/etc/"
sed -ni '/^[ \t]*CheckSpace/ !p' "$CHROOT_DIR/etc/pacman.conf"
sed -i "s/^[ \t]*SigLevel[ \t].*/SigLevel = Never/" "$CHROOT_DIR/etc/pacman.conf"
echo "Server = $MIRROR/\$repo/os/$ARCH" >> "$CHROOT_DIR/etc/pacman.d/mirrorlist"

chroot $CHROOT_DIR /usr/bin/pacman -Sy 
chroot $CHROOT_DIR /bin/bash

Method 4: Install pacman natively on non-arch distro (advanced)

Warning: This method is potentially difficult, your mileage may vary from distro to distro. If you just want to do an arch installation from another distro and you are not interested in have pacman as a regular program under such distro, is better to use a different method.

This method is about installing pacman and the arch install scripts directly under another distro, so they become regular programs on that distro.

This is really useful if you are planning to use another distro regularly to install arch linux, or do fancy things like updating packages of an arch installation using another distro. This is the only method that not imply creating a chroot to be able to execute pacman and the arch install scripts. (but since part of the installation includes entering inside a chroot, you'll end using a chroot anyway)

Download pacman source code and pacman packages

Visit the pacman homepage: and download the latest release.

Now, download the following packages:

Install dependencies

Using your distribution mechanisms, install the required packages for pacman and the arch install scripts. libcurl, libarchive, fakeroot, xz, asciidoc, wget, and sed are among them. Of course, gcc, make and maybe some other "devel" packages are necessary too.

Compile pacman

  • Decompress the pacman source code and cd inside.
  • Execute configure, adapting the paths as necessary:
     ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --enable-doc

If you get errors here, chances are you are missing dependencies, or your current libcurl, libarchive or others, are too old. Install the dependencies missing using your distro options, or if they are too old, compile them from source.

  • Compile
  • If there were no errors, install the files
    make install
  • You may need to manually call ldconfig to make your distro detect libalpm.

Prepare configuration files

Now is time to extract the configuration files. Change the x86_64 as necessary.

  • Extract the pacman.conf and makepkg.conf files from the pacman package, and disable signature checking:
    tar xJvf pacman-*-x86_64.pkg.tar.xz etc -C / ; sed -i 's/SigLevel.*/SigLevel = Never/g' /etc/pacman.conf
  • Extract the mirror list:
    tar xJvf pacman-mirrorlist-*-any.pkg.tar.xz -C /
  • Enable some mirrors on /etc/pacman.d/mirrorlist
  • Extract the arch-install-scripts
    tar xJvf arch-install-scripts-*-any.pkg.tar.xz -C /

Another option is using the alien tool to convert the pacman-mirrorlist and arch-install-scripts (but no pacman) to native packages of your distro.

Fix the Pacman Signature Keyring

It is necessary to initialize pacman's keyring for signature checking.

This is done using

# pacman-key --init # read the note below!
# pacman-key --populate archlinux

However, when connected via SSH you might run out of entropy. In this case you can try something like

# cat /usr/bin/* > /dev/null &
# find / > /dev/null &

before executing pacman-key --init.

It might take some time. If nevertheless all this does help install haveged and run prior to pacman-key --init

# /usr/sbin/haveged -w 1024 -v 1

Setup the target system

At this point, follow the normal steps of Installation Guide. Remember to mount the destination partition under the /mnt of the chroot.

# pacstrap /mnt base base-devel
# # ...

Edit the fstab file

Probably the genfstab script won't work. In that case, you'll need to edit the /mnt/etc/fstab file by hand. You can use the content of /etc/mtab as reference.

Finish the Installation

Now just do the rest of the steps normally.

Tips and tricks

  • In case you want to replace an existing system, but can for some reason not use a LiveCD, since, e.g., you have no physical access to the computer, the following tip might help: If you manage to get ~500MB of free space somewhere on the disk (e.g. by partitioning a swap partition) you can install the new Archlinux system there, reboot into the newly created system and rsync the entire system to the primary partition. Finally don't forget to fix the bootloader configuration before rebooting.