reclaiming unavailable space on ext3 or 4 using tune2fs -m

Michael Torrie torriem at
Sun Sep 26 22:41:31 MDT 2010

On Ext2,3 or 4, the file system reserves a certain number of blocks that
can only be allocated by privileged processes (root?).  When you do a
df, this percentage is taken into account and counts against free space.
 On a mount that is not the root file system, and will never have any
system process writing to it, you can free up some of this space for use
by normal users.  To do this, you can do (even on a mounted file system):

tune2fs -m 0 /dev/path/to/dev

So on my machine I always mount /home from a separate file system.  On
my mythtv box I also keep my recordings on separate file systems from my
root file system.  Running this command on my home workstation got back
30 odd GB of previously unusable space, and on my myth box, I got back
about 45 GB on each 1 TB disk.

Thought I'd pass along this tip.

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