Install Arch Linux from existing Linux

Follow Installation guide#Installation.

In the procedure, the first step, Installation guide#Select the mirrors, can be skipped since the host should already have a correct mirrorlist.

It is possible to replicate an existing Arch Linux installation by copying the host filesystem to the new partition and make some adjustments to it to make it bootable and unique.

The first step is to copy the host files into the mounted new partition, for this, consider using the approach exhibited in rsync#Full system backup.

Then, follow the procedure described in Installation guide#Configure the system with some caveats and additional steps:

• Installation guide#Time zone, Installation guide#Localization and Installation guide#Root password can be skipped
• Installation guide#Initramfs may be required in particular if changing filesystem, for example from ext4 to Btrfs
• Regarding Installation guide#Boot loader, it is necessary to reinstall the bootloader
• Delete /etc/machine-id so that a new, unique one, is generated at the next boot

If the mirrored Arch installation may be used within a different configuration or with another hardware, consider the following additional operations:

• Use the CPU microcode update adapted to the target system during the step Installation guide#Boot loader
• If any specific Xorg#Configuration was present on the host and may be incompatible with the target system, follow Moving an existing install into (or out of) a virtual machine#Disable any Xorg-related files
• Make any other adjustment appropriate to the target system, like reconfiguring the network or the audio.

Pacman can be compiled on most Linux distributions, and used directly on the host system to bootstrap Arch Linux. The arch-install-scripts should run without issues directly from the downloaded sources on any recent distribution.

Some distributions provide a package for pacman and/or arch-install-scripts in their official repositories which can be used for this purpose. As of July 2020, Void Linux is known to provide the pacman package, and Alpine Linux and Fedora are known to provide both pacman and arch-install-scripts.

Two methods to setup and enter the chroot are presented below, from the easiest to the most complicated. Select only one of the two methods. Then, continue at #Using a chroot environment.

Download the bootstrap tarball from a mirror into .

Download the bootstrap tarball signature from the download page and place it in the same directory. Do not download it from a mirror.

Verify the signature with GnuPG.

Extract the tarball:

# tar xzf /path-to-bootstrap-image/archlinux-bootstrap-x86_64.tar.gz --numeric-owner

Take note of the final option, which is important for preserving correct UID and GID numbers of extracted files in case your existing Linux system uses different numbers than Arch Linux.

Select a repository server by editing .

Enter the chroot:

• If bash 4 or later is installed, and unshare supports the and options:
• Otherwise, run the following commands:

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

The root image can be found on one of the mirrors under . The squashfs format is not editable, so we unsquash the root image and mount it.

To unsquash the root image, run

# unsquashfs airootfs.sfs

Select a repository server by editing squashfs-root/etc/pacman.d/mirrorlist.

Before chrooting to the unsquashed root image, we need to set up some mount points and copy the for networking.

# mount --bind squashfs-root squashfs-root
# mount -t proc none squashfs-root/proc
# mount -t sysfs none squashfs-root/sys
# mount -o bind /dev squashfs-root/dev
# mount -o bind /dev/pts squashfs-root/dev/pts  ## important for pacman (for signature check)
# cp -L /etc/resolv.conf squashfs-root/etc  ## this is needed to use networking within the chroot

Now, everything is prepared to chroot into the newly installed Arch environment:

# chroot squashfs-root bash

The bootstrap environment is really barebones (no nano or ). Therefore, we need to set up pacman in order to download other necessary packages.

Before starting the installation, pacman keys need to be setup. Before running the following two commands, read pacman-key#Initializing the keyring to understand the entropy requirements:

# pacman-key --init
# pacman-key --populate

Refresh the package lists and install what you need: , etc.

You can now proceed to Installation guide#Mount the file systems and follow the rest of the Installation guide.

Some host systems or configurations may require certain extra steps. See the sections below for tips.

On some Debian-based host systems, pacstrap may produce the following error:

This is because in some versions of Debian, points to while in the Arch-based chroot, does not exist and the link is broken. To correct this error, create a directory :

# mkdir /run/shm

While installing archlinux-2015.07.01-x86_64 from a Debian 7 host, the following error prevented both and arch-chroot from working:

Apparently, this is because these two scripts use a common function. chroot_setup() relies on newer features of , which are incompatible with Debian 7 userland (see ).

The solution for pacstrap is to manually execute its various tasks, but use the regular procedure to mount the kernel filesystems on the target directory ():

# newroot=/mnt
# mkdir -m 0755 -p "$newroot"/var/{cache/pacman/pkg,lib/pacman,log} "$newroot"/{dev,run,etc}
# mkdir -m 1777 -p "$newroot"/tmp
# mkdir -m 0555 -p "$newroot"/{sys,proc}
# mount --bind "$newroot" "$newroot"
# mount -t proc /proc "$newroot/proc"
# mount --rbind /sys "$newroot/sys"
# mount --rbind /run "$newroot/run"
# mount --rbind /dev "$newroot/dev"
# pacman -r "$newroot" --cachedir="$newroot/var/cache/pacman/pkg" -Sy base base-devel ... ## add the packages you want
# cp -a /etc/pacman.d/gnupg "$newroot/etc/pacman.d/"       ## copy keyring
# cp -a /etc/pacman.d/mirrorlist "$newroot/etc/pacman.d/"  ## copy mirrorlist

Instead of using arch-chroot for Installation guide#Chroot, simply use:

# chroot "$newroot"

Trying to create LVM logical volumes from an environment on a Debian 7 host resulted in the following error:

(Physical volume and volume group creation worked despite being displayed.)

This could be easily worked around by creating the logical volumes outside the chroot (from the Debian host). They are then available once chrooted again.

Also, if the system you are using has lvm, you might have the following output:

This is because debian does not use lvmetad by default. You need to edit and set to :

use_lvmetad = 0

This will trigger later an error on boot in the initrd stage. Therefore, you have to change it back after the grub generation. In a software RAID + LVM, steps would be the following:

• After installing the system, double check your Mkinitcpio and your bootloader settings. See Arch boot process#Boot loader for a list of bootloaders.
• You may need to change your /etc/mdadm.conf to reflect your RAID settings (if applicable).
• You may need to change your and according to your LVM and RAID requirements: MODULES="dm_mod" HOOKS="base udev mdadm_udev ... block lvm2 filesystems ..."
• You will most likely need to generate new initrd images with mkinitcpio. See Mkinitcpio#Image creation and activation.
• Set in .
• Update your bootloader settings. See your bootloader's wiki page for details.
• Set in .

On Fedora based hosts and live USBs you may encounter problems when using genfstab to generate your fstab. Remove duplicate entries and the "seclabel" option where it appears, as this is Fedora-specific and will keep your system from booting normally.

Check , or to find your swap partition. Assuming your hard drive is located on ( will be a number).

Do the following:

Disable the swap space:

# swapoff /dev/sdaX

Create a filesystem on it

# fdisk /dev/sda
(set /dev/sdaX ID field to "Linux" - Hex 83)
# mke2fs -j /dev/sdaX

Create a directory to mount it in

# mkdir /mnt/newsys

Finally, mount the new directory for installing the intermediate system.

# mount -t ext4 /dev/sdaX /mnt/newsys

Install essentials packages and any other package required to get a system with internet connection up and running in the temporary partition, being careful with the limit of ~700 MB space. When specifying packages to be installed with pacstrap, consider adding the -c flag to avoid filling up valuable space by downloading packages to the host system.

Once the new Arch Linux system is installed, fix the bootloader configuration, then reboot into the newly created system, and rsync the entire system to the primary partition.