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

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