# Nspawn Containers

[Arch Linux Wiki for Nspawn Containers](https://wiki.archlinux.org/index.php/Systemd-nspawn)

### Create a FileSystem

```bash
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

```bash
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.

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


```text
# /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.

```bash
# 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

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

[Network]
Bridge=br0
```

```bash
# 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

```bash
# 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](https://wiki.archlinux.org/index.php/locale)