Installing ArchLinux inside an Alpine chroot

It's sometimes useful to have another Linux system installed inside a chroot on an Alpine system. This page explains how to install a recent version of ArchLinux (either x86 or x86_64) inside an existing Alpine system (assumed to have the same architecture).

Some useful links:

• https://wiki.archlinux.org/title/Remote_Arch_Linux_Install
• https://wiki.archlinux.org/title/Install_from_Existing_Linux
• https://wiki.archlinux.org/title/Installation_Guide
• What's the proper way to prepare chroot to recover a broken Linux installation?

1. Inside your Alpine system:

   sudo apk add bash zstd curl wget # BusyBox wget is inadequate wget --no-check-certificate https://raw.github.com/tokland/arch-bootstrap/master/arch-bootstrap.sh mkdir chroot64 sudo bash arch-bootstrap.sh -a x86_64 chroot64

2. Then chroot into the newly-created Arch system. I use the following script to do this:

   Contents of /usr/local/bin/start-chroot

   #!/bin/sh -e user=`whoami` if [ "$user" != "root" ]; then echo "This script needs root access" >&2 exit 1 fi if ! [ -d "$1" ]; then echo "Usage: $0 <chroot directory>" >&2 exit 1 fi if [ x1 = x`sysctl -ne kernel.grsecurity.chroot_deny_chmod` ]; then echo "Warning: can't suid/sgid inside chroot" >&2 fi if [ x1 = x`sysctl -ne kernel.grsecurity.chroot_deny_chroot` ]; then echo "Warning: can't chroot inside chroot" >&2 fi if [ x1 = x`sysctl -ne kernel.grsecurity.chroot_deny_mknod` ]; then echo "Warning: can't mknod inside chroot" >&2 fi if [ x1 = x`sysctl -ne kernel.grsecurity.chroot_deny_mount` ]; then echo "Warning: can't mount inside chroot" >&2 fi cd "$1" shift cp -L /etc/resolv.conf ./etc/ || true mount -t proc proc ./proc mount -t sysfs sys ./sys mount -o bind /dev ./dev # next line is said to be important for pacman's signature check mount -o bind /dev/pts ./dev/pts case $1 in -l) shift;; -l*) one=${1#-l}; shift; set -- -$one "$@";; esac chroot . /bin/sh -l "$@" umount ./dev/pts umount ./dev ./sys ./proc

   At least when setting the Arch system up, you'll want to disable Alpine's grsecurity prohibition against suid/sgid:

   sysctl -w kernel.grsecurity.chroot_deny_chmod=0

   For more info, see:

   • https://en.wikibooks.org/wiki/Grsecurity
   • https://www.gentoo.org/proj/en/hardened/grsecurity.xml

3. Inside the Arch chroot, do the following. (The first step may take a long time, especially if you're connected to the system in question by ssh. See this link for more info, and tips about how to speed the process up.)

   pacman-key --init pacman-key --populate archlinux pacman -Syyu pacman -Rs systemd # inside a chroot, we don't need an init system (nor a kernel) pacman -S sudo

   You can also install any other packages you want. I use:

   pacman -S less licenses man-db man-pages procps-ng psmisc sysfsutils \ base-devel openssh cpio elfutils rsync unzip vim wget zip

4. Still inside the Arch chroot, assign a root password and create a non-root user:

   passwd useradd -m -g users -G wheel -s /usr/bin/bash myuser passwd myuser export VISUAL=/usr/bin/vim visudo

   Uncomment this line in /etc/sudoers, then save the file:

   ## Uncomment to allow members of group wheel to execute any command
   %wheel ALL=(ALL) ALL
   

Now you're done. You can switch to the non-root user with:

su - myuser

or hit Ctrl+D to exit the chroot.

If you'll want to install any packages from the Arch User Repository, you may want to install a richer package manager, such as Yaourt. Do this as the non-root user:

curl -O https://aur.archlinux.org/packages/pa/package-query/package-query.tar.gz tar -xzf package-query.tar.gz && cd package-query && makepkg -si cd .. curl -O https://aur.archlinux.org/packages/ya/yaourt/yaourt.tar.gz tar -xzf yaourt.tar.gz && cd yaourt && makepkg -si