Jul 022015
 

Time has come, I need to start switching my mentality from SysV to modern init systems. Turns out, that systemd thingy is not so bad! Actually, it’s pretty cool.

There is an interesting video from RedHat Summit 2015 (at the bottom of this page) which I wholeheartedly recommend, especially it doesn’t solely apply to Red Hat – Debian Jessie uses systemd too.

My notes for impatient:

 

  • Slice (each gets CPUShares=1024)
    user.slice
    system.slice # services
    machine.slice #vms, containers, etc
  • Scope
  • Service

 

systemctl list-unit-files --no-pager|grep lvm
systemctl -t service list-unit-files
systemctl -t service
systemctl -t socket
systemctl -t socket list-unit-files
systemctl get-default
systemctl set-default multi-user  # runlevel 3, no GUI
systemctl set-default graphical.target # aka runlevel 5, graphical.target
systemctl list-timers # can be used to periodically run fstrim for example?
systemd-delta # what changed on system comparing to originally shipped by distributor
systemctl rescue
systemctl emergency
systemd-cgtop # this is cool!
systemd-cgls
journalctl # logging. Trusted and untrusted fields in logs, untrusted are generated by logging app
journalctl -xn
journalctl -k -b -1
journalctl /dev/sda
journalctl /usr/bin/python-thinlinc
journalctl _SYSTEMD_UNIT=avahi-daemon.service

Checkout systemd based containers! Didn’t expect that

man systemd-nspawn
mkdir /var/lib/container/debian-tree
debootstrap --arch=amd64 unstable /var/lib/container/debian-tree/
systemd-nspawn -D /var/lib/container/debian-tree/

or assuming you have a bridge

systemd-nspawn --network-bridge=br-eth0 -D /var/lib/container/ka-lite

This installs a minimal Debian unstable distribution into the directory /var/lib/container/debian-tree/ and then spawns a shell in a namespace container in it. Wow. I know you can use like Linux Containers but this systemd-nspawn is already there waiting to be used.

Have fun.


 

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