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This document is a WORK IN PROGRESS.
This is just a quick personal cheat sheet: treat its contents with caution!

Ubuntu management

Reference(s)

Table of contents

How to remove avahi daemon from Ubuntu

avahi is the open-source implementation of zeroconf, used for automatic management of networks without any centralized configuration. Generally, avahi is only useful in small local networks (such as a home LAN).

The avahi-daemon process handles mDNS, which is used for name resolution and service discovery within the local network. If you don't need its functions, avahi can be safely removed.

Local name resolution allows you to reach the computer by a host name.local name without any centralized configuration. Since your server most likely has a DNS name, this function is unnecessary.

Service discovery allows programs to find and advertise running services (for example, to allow listing all SSH or PulseAudio servers in the LAN). This is convenient on a home network, but entirely useless for a data center hosted server. This too can be safely removed like so:

$ sudo systemctl stop avahi-daemon
$ sudo systemctl disable avahi-daemon
$ sudo vi /etc/default/avahi-daemon
    > ...
    > AVAHI_DAEMON_DETECT_LOCAL=0
    > ...

$ sudo apt purge avahi-daemon
$ sudo apt --purge autoremove

How to remove snap from Ubuntu

  • List snap packages ("snaps"): 

    $ snap list

  • Remove all installed snaps: 

    $ sudo for p in $(snap list | awk '{print $1}'); do sudo snap remove $p; done

  • Cleanup the core package: 

    $ sudo systemctl stop snapd
$ for m in /snap/core/*; do sudo umount $m; done
$ sudo snap remove core
    If anything remains, the steps below will take care of it.

  • Uninstall snapd: 

    $ sudo apt autoremove --purge snapd

  • Remove leftover directories: 

    $ rm -rf ~/snap
$ sudo rm -rf /snap
$ sudo rm -rf /var/snap
$ sudo rm -rf /var/lib/snapd
$ sudo rm -rf /var/cache/snapd

  • Block future installs: 

    $ sudo vi /etc/apt/preferences.d/no-snapd.pref
    > Package: snapd
    > Pin: origin ""
    > Pin-Priority: -10

Switch from Gnome to Xfce (and vice versa)

  • Install Xfce for Ubuntu: 

    $ sudo apt install xubuntu-desktop # or `sudo apt install xfce4 xfce4-goodies` if you prefer a more "vanilla" Xfce

  • Now, at login, in your display manager, you can switch from Gnome to Xfce

Switch from GDM to LightDM (and vice versa)

  • Install lightdm: 

    $ sudo apt install lightdm

  • Select lightdm as default display manager and reboot: 

    $ sudo dpkg-reconfigure lightdm
$ sudo reboot

    Or select gdm as default display manager and reboot: 

    $ sudo dpkg-reconfigure gdm3
$ sudo reboot

Troubleshooting

Headphone sound always muted

If your headphone sound is always muted (for example after an update), even when trying to mix the sound, e.g. with pulsemixer or with pulseaudio volume control, then try to restore your sound card driver state from its configuration file: $ alsactl restore

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