Sunday, September 24, 2017

Systemd not so known options

We use systemd all the time to restart services and query for their status, but it can do a lot more than just that.

It can be used to analyse the boot time of the system (systemd-analyze), to display realtime information of the processes in a top like manner (systemd-cgtop), display the status of the whole system in a tree like manner (sudo systemctl status) and many more.

Of course none of these is new, you can do this in a number of different ways, but it seems systemd is replicating a number of other tools.

Tuesday, April 25, 2017

Following a symbolic link in linux

Sometimes a link is pointing to a link, that is pointing to a link etc. It is a pain to resolve all the links and find which is the final file.
But there is a command that you can use to make things easier, and it is called readlink.

readink -f filename will traverse all the paths and print out the final filename

Saturday, March 4, 2017

Moving a zfs pool from one disk to another

If we want to move a zfs pool with their full layout from one disk to another we can use the following approach

zfs snapshot -r pool_A@migrate
zfs send -R pool_A@migrate | zfs receive -F pool_B

zfs unmount oldpool/myfilesystem

And take a new snapshot.

zfs snapshot oldpool/myfilesystem@snapshot2

you can now do an incremental send of the difference between the two snapshots which should be very quick.

zfs send -i oldpool/myfilesystem@snapshot1 \
             oldpool/myfilesystem@snapshot2 | zfs receive newpool/myfilesystem

Wednesday, February 8, 2017

Converting markdown presentation to pdf

If we want to convert a presentation from markdown to pdf, while keeping the slide format we can use the following command:

pandoc -t beamer -s -o habitat-presentation.pdf habitat-presentation-pdf.md 

Saturday, January 21, 2017

Resuming an interrupted scp tranfer

If we stop an scp tranfer, we can resume it by using rsync in the following way:

rsync -P -e ssh local_file user@host:remote_file

Thursday, December 22, 2016

Copying streams to video/audio files using vlc

If you ever need to save a stream (either audio or video) to a file, you can do it by using vlc.

You will find more details here: http://www.dedoimedo.com/computers/vlc-streaming.html

Wednesday, December 7, 2016

Wifi analyzer

If by any chance, you would like to see what is the wifi state around you, in order for example to pick the best channel for your own wireless device, and you do not have a wifi analyzer in an android device, you do not need to look far.

NetworkManager has got you covered. Just execute:
nmcli d wifi

on your linux console and you are done.