Systemd

helpful commands

Names:

*A unit is a resource / service to be started or stopped.

Command line:

• systemctl start|stop <unit>
• systemctl --state=failed
  • Shows a list of services that failed to be started at boot
• systemctl status [unit]
• systemd-analyze blame
  • shows a sorted list of services; first is the one with longest start time
• systemd-analyze plot > x.svg && eog x.svg
  • creates a graphical version of the previous blame
• systemctl disable <unit>
  • disables a unit so that it will not be started on next boot

video conversion

with Ubuntu 14.04 ffmpeg is replaced with avconv

avconv - rotating a vido and removing yound

First you may wonder why this is useful for anybody. Well I use it mainly at work. We are producing hardware components with embedded OS systems inside. And for issue documentation it’s often easiest to make a video with your smartphone. But often such a video is 90? rotated (portrait mode) and it has sound. Sound is not really bad but it does not help to hear your colleagues in the background having fun with some other coding projects :)

Goal:

• Remove the sound from my recordings
• rotate the video so that it’s immediately correctly viewable on a normal desktop screen

avconv -i INFILENAME -vf "transpose=1" -an OUTFILENAME

-vf "transpose=1"

• 0 = 90CounterCLockwise and Vertical Flip (default)
• 1 = 90Clockwise
• 2 = 90CounterClockwise
• 3 = 90Clockwise and Vertical Flip

-an

disable audio

to strongly shrink file size but still usable

avconv -i MOV_0244.mp4 -vf "transpose=1,scale=480:720" -b:v 300k -an out.mp4

-b:v 400k limit video bitrate to max of 400 kbits/s

scale=480:720 scale the output to a size of 480x720 pixel