Run script monthly on systemd.

monthly-timer.sh

#!/bin/bash

cat << EOF > /etc/systemd/system/monthly.timer
[Unit]
Description=Run script monthly

[Timer]
OnCalendar=*-*-01 02:00:00

[Install]
WantedBy=timers.target
EOF

cat << EOF > /etc/systemd/system/monthly.service
[Unit]
Description=Run script monthly
Requires=docker.service

[Service]
Type=oneshot
ExecStart=/usr/local/bin/monthly.sh

[Install]
WantedBy=multi-user.target
EOF

cat << EOF > /usr/local/bin/monthly.sh
#!/bin/sh
docker restart ssserver-websocket
docker restart ssserver-grpc
docker restart trojan-server
EOF

chmod +x /usr/local/bin/monthly.sh
systemctl enable monthly.timer --now
systemctl list-timers --all