[Trouble shooting / Linux] The volume "Filesystem root" has only 0 bytes disk space remaining.

• For my case, used % of /var was 100%. Especially, /var/log/kern.log was almost 20GB and /var/log/syslog was also large.
  
• If you type as follows, you can find the log files which are very huge size.

$ ls -lSh /var/log

Solution

$ cd /var/log

$ sudo apt clear

$ sudo  apt autoremove --purge

• Set rotate number as 1 (e.g.,rotate 4 --> 1)

$ vi /etc/logrotate.conf 

# keep 4 weeks worth of backlogs
(before) rotate 4
(after) rotate 1

• Delete old backup and log files such as *.log.3.
• Empty (NOT REMOVE!!!) kern.log and syslog

$ sudo su
$ > kern.log
$ > syslog
$ > (dpkg.log, wtmp, lastlog and so on)
$ exit