Linux | Systemd units

Systemd is a suite of basic building blocks for a Linux system. It provides a system and service
manager that runs as PID 1 and starts the rest of the system.

The Netdata Agent monitors the systemd.automount units. The systemd_automount_units_state alert
indicates that one or more of the systemd.automount units have failed. A systemd automount unit “failed” when the service process returned error code on exit, or crashed, an operation timed out, or after too many restarts. The cause of a failed states is stored in a log.

Read More About systemd

Here is some useful information about systemd from wikipedia 1

Systemd includes features like on-demand starting of daemons, snapshot support, process tracking, and Inhibitor Locks. Systemd is not just the name of the init daemon, but also refers to the entire software bundle around it, which, in addition to the systemd init daemon, includes the daemons journald, logind and networkd, and many other low-level components. In January 2013, Poettering described systemd not as one program, but rather a large software suite that includes 69 individual binaries. As an integrated software suite, systemd replaces the startup sequences and runlevels controlled by the traditional init daemon, along with the shell scripts executed under its control. systemd also integrates many other services that are common on Linux systems by handling user logins, the system console, device hotplugging, scheduled execution (replacing cron), logging, hostnames and locales.

Like the init daemon, systemd is a daemon that manages other daemons, which, including systemd itself, are background processes. systemd is the first daemon to start during booting and the last daemon to terminate during shutdown. The systemd daemon serves as the root of the user space’s process tree. The first process (PID1) has a special role on Unix systems, as it replaces the parent of a process when the original parent terminates. Therefore, the first process is particularly well suited for the purpose of monitoring daemons.

Systemd executes elements of its startup sequence in parallel, which is theoretically faster than the traditional startup sequence approach. For inter-process communication (IPC), systemd makes Unix domain sockets and D-Bus available to the running daemons. The state of systemd itself can also be preserved in a snapshot for future recall.

Systemd’s core components include the following:

  • systemd is a system and service manager for Linux operating systems.

  • systemctl is a command to introspect and control the state of the systemd system and service
    manager. Not to be confused with sysctl.

  • systemd-analyze may be used to determine system boot-up performance statistics and retrieve
    other state and tracing information from the system and service manager.

See more on systemd.automount units

A unit configuration file whose name ends in .automount encodes information about a file system
automount point controlled and supervised by systemd. Automount units must be named after the
automount directories they control. For instance, the automount point /home/lennart must be
configured in a unit file home-lennart.automount. For details about the escaping logic used to
convert a file system path to a unit name see systemd.unit(5). Note that automount units cannot be
templated, nor is it possible to add multiple names to an automount unit by creating additional
symlinks to its unit file.

For each automount unit file a matching mount unit file (see systemd.mount(5) for details) must exist which is activated when the automount path is accessed. For instance, if an automount unit home-lennart.automount is active and the user accesses /home/lennart the mount unit home-lennart.mount will be activated. 2

References and Source
  1. systemd on wikipedia
  2. man page for systemd.automount

Troubleshooting Section:

General Approach

If an automount has failed, then you should always try to collect more information to diagnose the cause of the failure.

  1. Identify which automount fails. Open the Netdata dashboard, find the current active alarms under the active alarms tab and look into its chart. (systemdunits_automount_units.automount_unit_state). In this chart, identify which automount units are in state with value 5

  2. Gather more information about the failing automount. We advise you to run the following commands
    in two different terminals.

    root@netdata~ # journalctl -u <automount_name>.automount -f 
    root@netdata~ # journalctl -u <automount_name>.mount -f 
  3. In your main terminal, try mount the automount manually.

    root@netdata~ # mount -v <automount_name> 

    This command will try to mount your automount unit in verbose mode.

  4. Check the output messages from both terminals for abnormalities.