Creating a 'run once' systemd unit.

README.md

Unit file for bringing up vxlan tunnel and adding it to a bridge after Zero Tier Interface is available

• https://toggen.com.au/it-tips/how-to-login-to-a-corporate-lan-when-you-are-a-thousand-km-away-and-dont-have-a-vpn/

Creating a 'run once' systemd unit

Systemd unit template which calls a script exactly once on startup and keeps unit status active after script exits.

Unit file placed in /etc/systemd/system and enabled with:

$ sudo systemctl enable runonce.service
$ sudo systemctl start runonce.service

Reference

• https://www.freedesktop.org/software/systemd/man/systemd.service.html#Type=
• https://www.freedesktop.org/software/systemd/man/systemd.service.html#RemainAfterExit=

toggen-vxlan.service

[Unit]
Description=Toggen VXLAN
# After=zerotier-one.service
# Wants=network-online.target
BindsTo=sys-devices-virtual-net-ztabcdefgh.device
After=sys-devices-virtual-net-ztabcdefgh.device

[Service]
# ExecPreStart=/bin/sleep 30
ExecStart=/usr/local/sbin/zt_install.sh
RemainAfterExit=true
Type=oneshot

[Install]
WantedBy=multi-user.target

brctl show

Before ExecPreStart vxlan100 interface is missing after boot.

bridge name     bridge id               STP enabled     interfaces
br100           8000.5636f58f8d97       no              ens192

After putting ExecPreStart

bridge name     bridge id               STP enabled     interfaces
br100           8000.5636f58f8d97       no              ens192
                                                        vxlan100

ZT Interface was NOT fully up when the zerotier-one.service was live so had to change to look for the interface being up.

use this command to find the zero tier interface unit

 systemctl list-units | grep zt

Output

 sys-devices-virtual-net-ztabcdefgh.device                                                 loaded active plugged   /sys/devices/virtual/net/ztabcdefgh
 sys-subsystem-net-devices-ztabcdefgh.device                                               loaded active plugged   /sys/subsystem/net/devices/ztabcdefgh

Add BindsTo and After

[Unit]
Description=Toggen VXLAN
# After=zerotier-one.service
# Wants=network-online.target
BindsTo=sys-devices-virtual-net-ztabcdefgh.device
After=sys-devices-virtual-net-ztabcdefgh.device