Nspawn Containers

Arch Linux Wiki for Nspawn Containers

Create a FileSystem

cd /var/lib/machines
# create a directory
mkdir <container>
# use pacstrap to create a file system
pacstrap -i -c -d <container> base --ignore linux

First boot and create root password

systemd-nspawn -b -D <container>
passwd
poweroff
# if you want to nat the container add *-n* flag
systemd-nspawn -b -D <container> -n
# and to bind mount the package cache
systemd-nspawn -b -D <container> -n --bind=/var/cache/pacman/pkg

Networking

On Arch, assuming you have systemd-networkd and systemd-resolved set up correctly, networking from the host end of things should just work.
However on Linode it does not. What does work on Linode is to create a bridge interface. Two files for br0 will get the job done.

# /etc/systemd/network/50-br0.netdev
[NetDev]
Name=br0
Kind=bridge

# /etc/systemd/network/50-br0.netdev
[Match]
Name=br0

[Network]
Address=10.0.55.1/24
DHCPServer=yes
IPMasquerade=yes

Notice how the configuration file tells systemd-networkd to offer DHCP service and to perform masquerade. You can modify the systemd-nspawn command to use the bridge interface. Every container attached to this bridge will be on the same subnet and able to talk to each other.

# first restart systemd-networkd to bring up the new bridge interface
systemctl restart systemd-networkd
# and add --network-bridge=br0 to systemd-nspawn command
systemd-nspawn -b -D <container> --network-bridge=br0 --bind=/var/cache/pacman/pkg

Automatically Starting the Container

There are two ways to automate starting the container. You can override systemd-nspawn@.service or create an nspawn file.

First enable machines.target

# to override the systemd-nspawn@.service file
cp /lib/systemd/system/systemd-nspawn@.service /etc/systemd/system/systemd-nspawn@<container>.service

Edit /etc/systemd/system/systemd-nspawn@<container>.service to add the systemd-nspawn options you want to the ExecStart command.

Or create /etc/systemd/nspawn/<container>.nspawn

# /etc/systemd/nspawn/<container>.nspawn
Bind=/var/cache/pacman/pkg

[Network]
Bridge=br0

# in either case
systemctl start/enable systemd-nspawn@<container>
# to get a shell
machinectl shell <container>
# and then to get an environment
bash

Initial Configuration Inside The Container

# set time zone if you don't want UTC
timedatectl set-timezone <timezone>
# enable ntp, networktime
timedatectl set-ntp 1

If you want to change the locale

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