infrastructure-documentation/lxc.md

## LXC Hosts

All LXC hosts are setup with [lxc-helpers](https://code.forgejo.org/forgejo/lxc-helpers/).

```sh
name=forgejo-host
lxc-helpers.sh lxc_container_run $name -- sudo --user debian bash
```

See https://github.com/mikesart/inotify-info. Running multiple LXC
containers will quickly use the default limit (128 on bookworm).

```sh
echo fs.inotify.max_user_instances=8192 | sudo tee -a /etc/sysctl.conf
sudo sysctl -p
```

### Unprivileged

```sh
name=forgejo-host
lxc-helpers.sh lxc_container_create --config "unprivileged" $name
echo "lxc.start.auto = 1" | sudo tee -a /var/lib/lxc/$name/config
lxc-helpers.sh lxc_container_start $name
lxc-helpers.sh lxc_container_user_install $name $(id -u) $USER
```

### Docker enabled

```sh
name=forgejo-host
lxc-helpers.sh lxc_container_create --config "docker" $name
echo "lxc.start.auto = 1" | sudo tee -a /var/lib/lxc/$name/config
lxc-helpers.sh lxc_container_start $name
lxc-helpers.sh lxc_install_docker $name
lxc-helpers.sh lxc_container_user_install $name $(id -u) $USER
```

### K8S enabled

```sh
name=forgejo-host
lxc-helpers.sh lxc_container_create --config "k8s" $name
echo "lxc.start.auto = 1" | sudo tee -a /var/lib/lxc/$name/config
lxc-helpers.sh lxc_container_start $name
lxc-helpers.sh lxc_container_user_install $name $(id -u) $USER
```

### Docker and LXC enabled

```sh
name=forgejo-host
ipv4=10.85.12
ipv6=fc33
lxc-helpers.sh lxc_container_create --config "docker lxc" $name
echo "lxc.start.auto = 1" | sudo tee -a /var/lib/lxc/$name/config
lxc-helpers.sh lxc_container_start $name
lxc-helpers.sh lxc_install_docker $name
lxc-helpers.sh lxc_install_lxc $name $ipv4 $ipv6
lxc-helpers.sh lxc_container_user_install $name $(id -u) $USER
```

## Hetzner

All hardware machines are running Debian GNU/linux bookworm. They are LXC hosts
setup with [lxc-helpers](https://code.forgejo.org/forgejo/lxc-helpers/).

> **NOTE:** only use [EX101 with a ASRockRack W680D4U-1L motherboard](https://forum.hetzner.com/index.php?thread/31135-all-ex101-with-asustek-w680-crash-on-sequential-read/).

### vSwitch

A vSwitch is assigned via the Robot console on all servers for backend communications
and [configured](https://docs.hetzner.com/robot/dedicated-server/network/vswitch#example-debian-configuration)
in /etc/network/interfaces for each of them with something like:

```
auto enp5s0.4000
iface enp5s0.4000 inet static
  address 10.53.100.2
  netmask 255.255.255.0
  vlan-raw-device enp5s0
  mtu 1400
```

The IP address ends with the same number as the hardware (hetzner02 => .2).

#### vSwitch DRBD

The vSwitch on VLAN 4000 is for DRBD exclusively

### DRBD

DRBD is [configured](https://linbit.com/drbd-user-guide/drbd-guide-9_0-en/#p-work) like in the following example with hetzner02 as the primary and hetzner03 as the secondary:

```sh
$ apt-get install drbd-utils
$ cat /etc/drbd.d/r0.res
resource r0 {
    net {
        # A : write completion is determined when data is written to the local disk and the local TCP transmission buffer
        # B : write completion is determined when data is written to the local disk and remote buffer cache
        # C : write completion is determined when data is written to both the local disk and the remote disk
        protocol C;
        cram-hmac-alg sha1;
        # any secret key for authentication among nodes
        shared-secret "***";
    }
    disk {
        resync-rate 1000M;
    }
    on hetzner02 {
        address 10.53.100.2:7788;
        volume 0 {
            # device name
            device /dev/drbd0;
            # specify disk to be used for device above
            disk /dev/nvme0n1p5;
            # where to create metadata
            # specify the block device name when using a different disk
            meta-disk internal;
        }
    }
    on hetzner03 {
        address 10.53.100.3:7788;
        volume 0 {
            device /dev/drbd0;
            disk /dev/nvme1n1p5;
            meta-disk internal;
        }
    }
}
$ sudo drbdadm create-md r0
$ sudo systemctl enable drbd
$ sudo systemctl start drbd
```

On hetzner02 (the primary), [pretend all is in sync](https://linbit.com/drbd-user-guide/drbd-guide-9_0-en/#s-skip-initial-resync) to save the initial bitmap sync since
there is actually no data at all.

```sh
sudo drbdadm new-current-uuid --clear-bitmap r0/0
```

The DRBD device is mounted on `/var/lib/lxc` in `/etc/fstab` there is a noauto line:

```
/dev/drbd0 /var/lib/lxc ext4 noauto,defaults 0 0
```

To prevent split brain situations a manual step is required at boot
time, on the machine that is going to be the primary.

```sh
sudo drbdadm primary r0
sudo drbdsetup status
sudo mount /var/lib/lxc
sudo lxc-autostart start
sudo lxc-ls -f
sudo drbdsetup status
```