Re: 3 seconds boot time?
Many times slow boot (or more accurately, time to reach "graphical.target") is due to waiting for the "network-online.target" which will only be reached on most laptops once the/a WiFi network is found and connected.
This is usually a side effect of configuring a Network Manager (WiFi) connection to be available to all system users which causes it to be brought up before desktop log-in is reached.
However, for the more general case systemd provides useful tools for identifying where boot-time delays occurred:
systemd-analyze critical-chain
systemd-analyze blame
By default these assume "--system" but with "--user" the user session start-up can be analysed separately.
"critical-chain" is the most useful when one service is delaying others, such as when waiting for a network connection to become available. The numbers show the @when and the +duration of each unit. E.g: on my laptop it takes +5.649s for the WiFi connection to be established:
graphical.target @11.614s
└─multi-user.target @11.614s
└─kerneloops.service @11.579s +34ms
└─network-online.target @11.570s
└─NetworkManager-wait-online.service @5.919s +5.649s
└─NetworkManager.service @5.419s +403ms
└─dbus.service @5.158s
└─basic.target @5.091s
(Bug alert: seems like ElReg's CODE and PRE tags do not preserve layout - the above should be indented and each line shouldn't be wrapped in P tags)
As always
man systemd-analyze
details many more useful reports and visualisations of the boot process and how to interpret the output.
Biting the hand that feeds IT
