====== Ubuntu - SystemD - Analysing performance problems with systemd ======

Systemd is the default init-system in fresh installations of Debian GNU/Linux.

One thing that Systemd is designed to do is speed up the booting of systems.  True most installations are "servers" and as-such they're rarely rebooted, but I've been living with and working with a Debian laptop and Debian desktop for the past few years - and the laptop gets shutdown every day, and for that reason it is interesting to see how long a boot takes, and where that time is taken.

Three interesting commands to look at the boot-speed of a system are:

  * systemd-analyze
  * systemd-analyze critical-chain
  * systemd-analyze blame

This allow you to see the times that are taken to start various things.  For example the second command on this laptop shows me:

<code bash>
The time after the unit is active or started is printed after the "@" character.
The time the unit takes to start is printed after the "+" character.
graphical.target @5.384s
└─multi-user.target @5.384s
  └─NetworkManager.service @5.105s +278ms
    └─basic.target @5.103s
      └─paths.target @5.103s
        └─acpid.path @5.103s
          └─sysinit.target @5.102s
            └─console-setup.service @5.047s +54ms
              └─kbd.service @5.024s +23ms
                └─remote-fs.target @5.023s
                  └─local-fs.target @5.022s
                    └─lvm2-monitor.service @4.995s +24ms
                      └─system.slice @70ms
                        └─-.slice @68ms
</code>

Similarly if I run the "systemd-analyze blame" command I can see that the longest stall is waiting for:

<code bash>
          4.548s systemd-cryptsetup@home.service
</code>

Most of this stall is waiting for me to enter the passphrase for my encrypted /home directory!