Installing ArchLinux inside an Alpine chroot

2024-11-20T17:54:49Z

Theresa: add missing dependencies

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 [https://www.archlinux.org/ 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
* [https://superuser.com/questions/111152 What's the proper way to prepare chroot to recover a broken Linux installation?]

<OL>
<LI><div>
Inside your Alpine system:
{{Cmd|<nowiki>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
</nowiki>}}

</div>
<LI><div>
Then chroot into the newly-created Arch system. I use the following script to do this:

{{Cat|/usr/local/bin/start-chroot|<nowiki>
#!/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
</nowiki>}}

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

{{Cmd|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

</div>
<LI><div>
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 [https://wiki.archlinux.org/title/Pacman-key#Initializing_the_keyring this link] for more info, and tips about how to speed the process up.)

{{Cmd|<nowiki>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
</nowiki>}}

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

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

</div>
<LI><div>
Still inside the Arch chroot, assign a root password and create a non-root user:

{{Cmd|<nowiki>passwd
useradd -m -g users -G wheel -s /usr/bin/bash myuser
passwd myuser
export VISUAL=/usr/bin/vim
visudo
</nowiki>}}

Uncomment this line in {{Path|/etc/sudoers}}, then save the file:

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

</div>
</OL>

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

{{Cmd|su - myuser}}

or hit {{Key|Ctrl}}+{{Key|D}} to exit the chroot.

If you'll want to install any packages from the [https://aur.archlinux.org/ Arch User Repository], you may want to install a richer package manager, such as [https://wiki.archlinux.org/index.php/Yaourt Yaourt]. Do this as the non-root user:

{{Cmd|<nowiki>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
</nowiki>}}

[[Category:Development]]
[[Category:Installation]]

Alpine Linux - User contributions [en]

Installing ArchLinux inside an Alpine chroot