It’s a proxmox hookscript.
Documentation is located here: hookscripts
You have to place it in /var/lib/vz/snippets and add it to the conf of your lxc at /etc/pve/lxc by adding (in my configuration)
hookscript: local:snippets/hook121.sh
I’m using this without any problems to automate ZFS zoning on my proxmox.
#!/bin/bash
vmId="$1"
runPhase="$2"
echo "Running $runPhase on VM=$vmId"
case "$runPhase" in
post-start)
pid=$( lxc-info -n $1 -p | awk '/PID:/{print $NF}' )
zfs zone /proc/$pid/ns/user sata/ct/urbackup
echo "zfs zone"
;;
pre-stop)
pid=$( lxc-info -n $1 -p | awk '/PID:/{print $NF}' )
zfs unzone /proc/$pid/ns/user sata/ct/urbackup
echo "zfs unzone"
;;
esac