Learn LXC - Autostart, Systemd & Service Management

#Introduction

Your containers can now be created, run, limited, and snapshotted. But there's one practical problem: after a host reboot, all containers stay down — unless we configure them. In episode 10 we make containers persist automatically: autostart on boot, management via systemd, and clean shutdown. This is what separates a lab container from real infrastructure services.

#Autostart: Containers Boot Along with the Host

#Configuration in the Container Config

Autostart is controlled by two keys in the container config:

/var/lib/lxc/c1/config (autostart)

lxc.start.auto = 1
lxc.start.delay = 5
lxc.start.order = 100

• lxc.start.auto = 1 — the container starts automatically on host boot.
• lxc.start.delay = 5 — a 5-second delay after this container starts (giving the database/network of earlier containers time to stabilize).
• lxc.start.order = 100 — start order; the smaller the number, the earlier (e.g. database order 50, web order 100).

#Autostart and Shutdown from the Command Line

sudo lxc-autostart

sudo lxc-autostart -s

lxc-autostart honors the configured lxc.start.order and lxc.start.delay.

#Systemd Integration

#The lxc@.service Unit

Modern LXC provides the lxc@.service systemd template unit that manages containers as registered services on the host. With this unit, all systemd controls work: enable, start, stop, status, and even startup ordering against other host services.

Enable autostart via systemd for container c1:

sudo systemctl enable lxc@c1.service
sudo systemctl start lxc@c1.service

Check its status like any service:

systemctl status lxc@c1.service

The advantages of this unit: container logs integrate with the host's journald, and systemd can guarantee start ordering against other units (e.g. lxc@db must run before the host nginx).

#lxc-autostart vs the systemd unit

• lxc-autostart — simple, uses the container config settings (lxc.start.auto), suitable for all-containers-boot scenarios.
• lxc@.service — explicit per container, can be systemctl enable/disabled individually, and integrates with systemd dependencies.

Many users use both together: lxc.start.auto for default behavior, the systemd unit for granular control. Be careful that duplicate configuration doesn't start a container twice — it's usually safe because LXC prevents double starts, but still check systemctl status.

#Services Inside the Container: systemd as init

#Full Boot with systemd

Modern containers (Ubuntu 24.04, Debian, Fedora) run systemd as init (PID 1) inside. That means services inside the container are managed like a regular Linux host: systemctl enable/start/status work normally inside the container.

Enter and manage services:

lxc-attach -n c1 -- systemctl status sshd
lxc-attach -n c1 -- systemctl enable --now sshd
lxc-attach -n c1 -- systemctl list-units --state=running

#Port Forwarding or Service Access

Once a service runs inside the container, access it from outside via port forwarding (episode 6) or directly via the container IP if the network is bridged:

lxc-info -n c1 -iH

#Stopping Containers: lxc-stop vs lxc-shutdown

#lxc-shutdown: Orderly Shutdown

lxc-shutdown sends a signal to the container's init (like pressing the power button on a desktop): systemd receives the shutdown command, stops services cleanly, then powers off. This is the most correct way to stop a container.

lxc-shutdown -n c1

#lxc-stop: Forced/Hard Stop

lxc-stop stops the container forcefully — equivalent to pulling the power cable. Use it when a container hangs or lxc-shutdown doesn't respond.

lxc-stop -n c1

#When to Use Which

• Default: lxc-shutdown so services close themselves down cleanly (important for databases).
• Container not responding: lxc-stop, then think about why shutdown didn't work.
• In automation scripts: try shutdown with a timeout, fall back to stop.

lxc-shutdown -n c1 -t 10 || lxc-stop -n c1

#Closing

Key takeaways:

• lxc.start.auto = 1 makes a container boot with the host; lxc.start.order and lxc.start.delay set the order and delay.
• lxc-autostart processes all containers with start.auto; lxc-autostart -s shuts them all down.
• The lxc@.service unit integrates containers into the host systemd with dependencies and journald logging.
• Modern containers run systemd as init; manage services inside with systemctl.
• lxc-shutdown for orderly shutdown, lxc-stop as a last resort.

In the next episode 11 we'll cover bind & mount host paths — lxc.mount.entry for mounting host directories into the container, mount options like ro, and the real-world case of sharing data directories and device access.