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systemd-nspawn Containers with Arch Linux

The following is a quick guide to create systemd-nspawn container, which is a super-powered chroot on Arch Linux. There are a ton of ways to pull down or create container images, as well as options to launch and control containers. The following is only a sample of what I use to quickly get started.

Build the container image

There are a number of tools or ways to create images. I use debootstrap:

sudo pacman -S debootstrap

This will demonstrate with an Ubuntu image. I need to pull down the base packages from an Ubuntu archive mirror:

$ sudo debootstrap --include=systemd-container --components=main,universe \
    focal ubuntu-focal https://mirror.enzu.com/ubuntu/
...
I: Base system installed successfully.
~ took 2m52s

This creates a Ubuntu Focal container in a folder called ‘ubuntu-focal’ using the specified mirror. Users can add and customize the container with any of the other debootsrap parameters as well.

Customize the image

Users can also copy any files directly into the directory structure at this point.

While optional, it is nice to set a password before booting the full system:

$ sudo systemd-nspawn -D ubuntu-focal/
Spawning container ubuntu on /home/powersj/ubuntu-focal.
Press ^] three times within 1s to kill container.
root@ubuntu:~# passwd
New password:
Retype new password:
passwd: password updated successfully
root@ubuntu:~# logout
Container ubuntu exited successfully.

Start the container

Finall, boot the container, using the -b flag to invoke init and complete a full boot pointing to the directory of the container we created:

$ sudo systemd-nspawn -b -D ubutnu-focal
Spawning container ubuntu-focal on /home/powersj/ubuntu-focal.
Press Ctrl-] three times within 1s to kill container.
systemd 245.4-4ubuntu3 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid)
Detected virtualization systemd-nspawn.
Detected architecture x86-64.

Welcome to Ubuntu 20.04 LTS!

...

Ubuntu 20.04 LTS x1c6 console

x1c6 login:

machinectl

The machinectl command is useful to out what containers are running as well as to manage other containers:

❯ machinectl
MACHINE      CLASS     SERVICE        OS     VERSION ADDRESSES
ubuntu-focal container systemd-nspawn ubuntu 20.04   -

1 machines listed.