UNIX for Beginners Questions & Answers

Hello,
I am running ubuntu 14.04.
Have just installed torrent into home directory but /dev/md2 is almost full.
Is it possible to resize md2 to get rid of any problem that may arise in the near future?

Code:

Filesystem      Size  Used Avail Use% Mounted on
udev             17G  4.1k   17G   1% /dev
tmpfs           3.4G  685k  3.4G   1% /run
/dev/md2         21G   20G  211M  99% /
none            4.1k     0  4.1k   0% /sys/fs/cgroup
none            5.3M     0  5.3M   0% /run/lock
none             17G     0   17G   0% /run/shm
none            105M     0  105M   0% /run/user
/dev/sda1       535M  156k  535M   1% /boot/efi
/dev/md3        4.0T  602G  3.2T  17% /home

The company gives a tutorial here showing how to mount extra disk into system. I am unable to use it as partition names are not the same..

PS: I have found a solution which saves my day but it would be better to learn how to resize RAID partition..

Thank you
Boris

First of all, learn to utilize volume groups.
Not matter of the backed devices (md devices, disk devices, fc luns etc), the flexibility offered is substantial.

As for your situation, you can replace all disks in array with bigger ones then grow.
Growing - Linux Raid Wiki

This will require work and has its risks, additional inspection should be done when dealing with root and boot filesystems (/)
For learning, pop a virtual machine, make similar setup and test the scenarios.

What i recommend is examining what is taking so much space on /dev/md2 21G 20G 211M 99% /
Clean up the space and/or make symlinks to /home from stuff which you pile in root filesystem, and it is not related to system, but your actions (torrents, downloads etc.)

Again, having volume group instead of /home over md device would have some advantages as well.

I would like to point out that having root on 99% is not advisable or prudent to have

Hope that helps
Regards
Peasant.

Thank you Peasant,
Removed unneccessary files and it's around 5% now but that'd not the case.
I will do some tests on a vps as you guided. I'll be back :/

Kind regards
Boris