Root Partition Filled Up After Upgrade (6 > 7)

You can see what takes space from the "Disk usage analyzer" (the command is 'baobab' if you do not want to search in the menus).

Two probable causes and solutions:

• You never remove the .deb packages and /var/cache/apt/archives/ eats up the space -> 'sudo apt-get clean' to remove all .deb files; 'sudo apt-get autoclean' to only keep those that relates to the latest versions;
• You kept many kernels (you only need the last one and, for safety, one older one you are sure it properly boots) -> remove the linux-image-*, linux-image-extra-* and linux-headers-* packages (for instance from the "Synaptic package manager" in the "System settings") that relate to versions of the kernel you do not need anymore (that can free close to 200MB per kernel).

Are you using btrfs? One time I tried it on my root partition and it filled up quickly due to its copy on write nature. It was a little while back though, so maybe the space issue was fixed in later kernels.

The TL;DR of my reply to Magic Banana is that I seem to have almost 10GB of logs in /var/log. Is it safe for me to just go into that folder and delete everything in there that's not a folder? Or is there is a special command for safely purging logs?

Also, the size of the logs seems to be growing constantly. I cleared some space with auto-remove and now my root partition is full again. I suspect this may be a bug. I will be able to confirm this once I can remove the logs, and see if they start to fill up the partition again. If so, I will file a bug report.

logrotate is used by the system to rotate logs, so you have two choices. You can either incorporate the rotation of these app logs into the systems rotations or setup your own and either run them manually or from the root user's crontab (Assuming the Rails app is run as root given it's directory is /root/)

To setup a logrotation within the system's pre-existing ones simply add a new file to the directory /etc/logrotate.d. Call it railsapp.conf. I'd use the other examples there to construct it. Also confrere with the logrotate man page.

User rotation

If you want to run your own instance of logrotate you only have to provide it with command line switches to do so.

First make a copy of:
/etc/logrotate.conf /root/rails_logrotate.conf
Edit the file so that it has the log rotation configured the way you want (i.e. keep all logs, rotate weekly, etc.)

Run it

# 1st time
$ logrotate -d -f -s $HOME/my_logrotate.state logrotate.conf

# afterwards
$ logrotate -d -s $HOME/my_logrotate.state logrotate.conf

If things look alright you can re-run these commands without the -d switch. This is for debugging purposes only and won't actually do any of the tasks, merely show you what it WOULD do.

$ logrotate -s $HOME/my_logrotate.state logrotate.conf

You could also use the -v switch to make it verbose, similar to the output seen when using the -d switch.

Example

Start with this log file.

$ dd if=/dev/zero of=afile bs=1k count=10k
10240+0 records in
10240+0 records out
10485760 bytes (10 MB) copied, 0.0702393 s, 149 MB/s

$ ll afile
-rw-rw-r-- 1 menomore menomore 10485760 Oct 26 14:37 afile

$ touch -t 201307010101 afile
$ ll afile
-rw-rw-r-- 1 menomore menomore 10485760 Oct 26 01:01 afile

Now run logrotate

$ logrotate -v -f -s $HOME/my_logrotate.state logrotate.conf
reading config file logrotate.conf
reading config info for /home/menomore/afile

Handling 1 logs

rotating pattern: /home/menomore/afile forced from command line (1 rotations)
empty log files are rotated, old logs are removed
considering log /home/menomore/afile
log needs rotating
rotating log /home/menomore/afile, log->rotateCount is 1
dateext suffix '-20130806'
glob pattern '-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]'
glob finding old rotated logs failed
renaming /home/menomore/afile to /home/menomore/afile-20130806
creating new /home/menomore/afile mode = 0664 uid = 500 gid = 501

Check the results

$ ll afile*
-rw-rw-r-- 1 menomore menomore 0 Oct 26 14:40 afile
-rw-rw-r-- 1 menomore menomore 10485760 Oct 26 01:01 afile-20130806

Weekly;

To make this run every Sunday you could create the following crontab entry for the root user.

$ crontab -e

Add the following lines:

# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * user-name command to be executed
0 0 * * sun logrotate -v -f -s $HOME/my_logrotate.state $HOME/logrotate.conf

Then save the above.

You can also use these types of shortcuts instead of specifying the actual days, mins, secs, etc.

string meaning
------ -------
@reboot Run once, at startup.
@yearly Run once a year, "0 0 1 1 *".
@annually (same as @yearly)
@monthly Run once a month, "0 0 1 * *".
@weekly Run once a week, "0 0 * * 0".
@daily Run once a day, "0 0 * * *".
@midnight (same as @daily)
@hourly Run once an hour, "0 * * * *".

I did this a while ago, I thiink my way COULD be wrong. But we all figure out how to, because what I googled confused me, so I needed to figure it out on my own. You can do it your own way, I guess.
If you like, a reference:
http://www.thegeekstuff.com/2010/07/logrotate-examples/

What is logrotate?

logrotate is a program used to rotate logs. The system usually runs logrotate once a day, and when it runs it checks rules that can be customized on a per-directory or per-log basis.

“Log rotation” refers to the practice of archiving an application’s current log, starting a fresh log, and deleting older logs. Because a “log” is a file where an application stores information that might be useful to an administrator or developer - what it’s been doing, what errors it’s run into, that sort of thing. So logs are good, you just usually don’t want to keep a ton of them around. That’s where logrotate comes in.

The importance of log rotation

Logs are wonderful things when you want to track usage or troubleshoot an application. Unfortunately the more information that gets logged, the more disk space the log uses. Over time it can really add up.

A log left unrotated can grow to a pretty unwieldy size. Running out of disk space because of a giant log is a problem of course, but a huge log file can also slow down the process of resizing or backing up. Another practical consideration is that it’s hard to look for a particular event if you have a million log entries to skim through. So on the whole it’s a good idea to keep log files down to a manageable size, and to prune them when they get too old to be of much use.

Fortunately logrotate makes log rotation easy.

Placing /var/log in its own partition or volume can help to mitigate the run-away disk usage. If you use audit, then having /var/log/audit on its own partition or volume helps to assure the audit logs are not affected.

tail -f /var/log/syslog will scroll the syslog (until it rotates) and let you see a little more of what's happening. If you do not want to do the logrotate.

I'd start by tailling the files and see what has most recently been writing to them, that might be enough of a clue. And then you can just echo blacklist the syslog.