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Linux disk full errors but disk has space

Linux disk full errors but disk has space

Desktops, Filesystems, Linux, Servers, Slider September 9, 2014 , by No Comments on Linux disk full errors but disk has space

Today I had a customer reporting a wordpress error when uploading images. "Missing a temporary folder"

Checked file permissions on /tmp – they were fine.

But is /tmp the location of the temporary folder for the site? Went to add a new file for a quick php_info(); and got a "disk space full error". Ahhh, that explains it.

Run "df -h" to check diskspace and the drives were between 0% – 18% full, loads of space.

But knowing the way that linux file systems work having encountered this issue before I know the problem and the solution.

Inodes

Inodes are a finite resource on most linux file systems which limit the total maximum number of files.

They work in a similar way to an index or table of contents at the start of a book.

Both the book and the index were created at the same time, completely empty but with a suitable number of index entries (inodes) for the pages (files) in the book.

On a normal system you run out of disk space well before you run out of inodes – this server had 38GB diskspace and 4.9 million inodes meaning an average file size of 7.7KB would fill disk and inodes perfectly.

But if you get a server with an unusually large number of extremely small files the inodes limit can be an issue.

Increasing inode limits will normally require reformatting the disk so not good for a production machine – so the fix is to delete files.

 

First I located the source of the majority of files (inodes).

cd /

for i in `ls -1A | grep -v "\.\./" | grep -v "\./"`; do echo "`find $i | sort -u | wc -l` $i"; done | sort -rn | head -10

This showed I had 4.7M inodes in /var

cd var

for i in `ls -1A | grep -v "\.\./" | grep -v "\./"`; do echo "`find $i | sort -u | wc -l` $i"; done | sort -rn | head -10

The files were all in /var/spool

cd spool

for i in `ls -1A | grep -v "\.\./" | grep -v "\./"`; do echo "`find $i | sort -u | wc -l` $i"; done | sort -rn | head -10

/var/spool/exim4 was the culprit with 95% of my available inodes in use.

I didn't use exim4 on this server, it got installed as a dependency of something else I was using, so fine to go ahead and clear them all.

rm -f exim4

Waiting, waiting and waiting. I probably would have got a "too many arguments" error but didn't wait that long.

cd exim4

find . -type f -print -delete

Using find worked more reliably and was less resource intensive when it comes to deleting a few million files.

# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/sda1 4980736 217861 4762875 5% /

Problem solved!

Mark Walker
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