Archive for March, 2015

Use systemd in Linux like a Pro – A cheat sheet

As systemd becomes the default method of handling services in all major Linux distributions, below are some quick and easy-to-remember commands that will make you look like a pro.

systemctl

  • check for all running units
    systemctl
    TIP: To show all units, including in-active ones:
    systemctl list-unit-files
  • Check for failed units
    systemctl --failed
  • Start, stop, restart units
    systemctl start postfix.service
    systemctl restart postfix.service
    systemctl stop postfix.service
  • Check status of a specific unit
    systemctl status mysqld.service
    TIP: Use -l for detailed status
  • Enable or disable services
    systemctl enable firewalld.service
    systemctl disable NetworkManager.service
    TIP: If you disable a service, and it still runs,
    systemctl mask NetworkManager.service
    Use ‘unmask’ to restore it
  • See if a specific unit is enabled
    systemctl is-enabled iptables.service
  • Create a snapshot – useful for testing various targets
    systemctl snapshot example.snapshot
    TIP: To activate it:
    systemctl isolate example.snapshot
  • Reboot/poweroff/suspend your machine
    systemctl reboot
    systemctl poweroff
    systemctl suspend
  • Change current target – i.e. runlevel
    systemctl isolate graphical.target
  • To list current target
    systemctl list-units --type=target

systemd

  • See which units take a long time to start during boot up
    systemd-analyze blame
    TIP: You can plot the boot up using:
    systemd-analyze plot
  • See when a unit started and how long it took
    systemd-analyze critical-chain

journalctl

  • Create a running log like ‘tail -f /var/log/messages’
    journalctl -f -o cat --no-pager
  • Running log for a specific unit
    journalctl -f -o cat --no-pager -u httpd.service
  • See boot messages – like ‘dmesg’
    journalctl -b

Manage remote systems:
systemctl status sshd -H root@1.2.3.4

For detailed instructions on these and more commands, man as always is your best friend.

Uganda’s popular TV channels currently off the Digital TV (OTA) spectrum

Uganda’s traditionally most watched TV stations, Nation TV (NTV) and Wavah Broadcasting services (WBS) are currently off the UCC assigned Over-the-Air digital TV frequency, 474MHz. WBS TV has been off for nearly a month now, while NTV’s feed went off last week, with a brief return on Tuesday evening. Since, most Ugandans are still using analogue (and a few using Pay-TV-services), these blackouts on the Kampala Free-to-Air Digital TV transmission multiplex have gone pretty much unnoticed. Check out the current status for all Free-to-Air Digital TV Channels.

With all the questions surrounding the ability of Signet, the sole distributor of the Digital TV signals in Uganda , it is sad to see that some of Uganda’s major digital TV channels are off or barely on at this very late stage.
Signet, which was spawned from the national public broadcaster, Uganda Broadcasting Corporation (UBC) and contracted to handle the Digital TV signal distribution through out Uganda.

It would be nice to see all the parties responsible for digital TV migration in Uganda (i.e. Signet, Uganda Communications Commission, and broadcasters) aggressively updating the country, on where we are regularly especially now that we are quickly approaching the June switch off deadline.