Calculating the size of /

Jim Byrnes jf_byrnes at
Tue Sep 11 00:20:17 UTC 2012

On 09/10/2012 04:30 PM, PleegWat wrote:
> Hash: SHA1
> On 09/10/2012 09:03 PM, Jim Byrnes wrote:
>> In another thread I was trying to calculate how much disk space to
>> allocate to / if I did a fresh install and this time setup  a
>> separate /home partition.
>> To get an idea of how much was outside of the home folder on my
>> present install I did:
>> sudo du -shc /  =>  105GB du -shc /home   =>  64GB
>> This led me to believe I had 105GB - 64GB = 41GB that would be in
>> /.
>> Colin suggested I run Disk Usage Analyzer:
>> Total filesystem capacity: 264.7GB(used: 104.5GB avail: 160.2GB
>> /        100%        75.3GB home        84.1%        63.3GB usr
>> 6.7%        5.0GB var        5.8%        4.4GB lib        2.1%
>> 1.6GB opt        1.0%        762.2MB boot        0.3%
>> 194.6MB
>> Everything else was 0.0%
>> So this seems to say that if I had a separate /home on this machine
>> that / would be 12GB not the 41GB calculated above.
>> So what accounts for the difference of 29.2GB between the used of
>> 104.5GB and / of 75.3GB?
>> The 12GB and 29.2GB = the 41GB I originally calculated would be
>> needed for /.  12GB seems to be more in line with what others
>> reported as the size needed for /.
>> Regards,  Jim
> Hi,
> The 105 GB is probably correct, since it matches the total filesystem
> usage reported by Disk Usage Analyzer
> The list returned by disk usage analyzer is probably off because of
> data in directories your normal login user cannot read. This may
> include data in root's home and trash, certain log directories, and
> other users' data. Given that we're talking about 29GB, another user
> account is the only thing that seems likely.
> Another user would have his own directory under /home. Other
> directories containing data not readable by your user may be
> discoverable running disk usage analyzer as root (Alt-F2, 'gksu baobab')
> You can also drill down using the --max-depth=1 option to du.
> PleegWat

Your analysis appears to be correct.  I am the only user but the problem 
is in root's home and trash, as below:

/				100%				42.9GB
root				67.5%			28.9GB
   .local			  99.8%			  28.9GB
     share			100.0%			28.9GB
       trash			  100.0%			  28.9GB
         files			100.0%			28.9GB
           backintime		  99.9%			  28.9GB
.virtualbox/HardDisks	99.7%			28.3GB

I use backintime to do backups to an external usb drive. Back in April 
it was getting full so I used backintime to delete some backup sets. 
Somehow they seem to have ended up under root.

I emptied the trash and reran the analysis.  Some of the numbers changed 
but the 28GB is still under root.  I even rebooted but it is still 
there.  How can I get rid of that 28GB?

Regards,  Jim

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