First off look at what you’ve got now:
[root@sql2 ~]# df -P / Filesystem 1024-blocks Used Available Capacity Mounted on /dev/mapper/VolGroup00-LogVol00 81269424 66551212 10534464 87% /
Then check how much is reserved blocks for root:
[root@sql2 ~]# tune2fs -l /dev/mapper/VolGroup00-LogVol00 | egrep 'Block count|Reserved block count' Block count: 20971520 Reserved block count: 1045937
Thats 5%, which is a pretty common default. Like a lot of old defaults its based on old hardware, we can get away with a lot less and I could use the space elsewhere (SSD is expensive). So lets tune it down to 1%:
[root@sql2 ~]# tune2fs -m 1 /dev/mapper/VolGroup00-LogVol00 tune2fs 1.39 (29-May-2006) Setting reserved blocks percentage to 1% (209715 blocks)
Verify that:
[root@sql2 ~]# tune2fs -l /dev/mapper/VolGroup00-LogVol00 | egrep 'Block count|Reserved block count' Block count: 20971520 Reserved block count: 209715
Looks good, lets see how much space we got:
[root@sql2 ~]# df -P / Filesystem 1024-blocks Used Available Capacity Mounted on /dev/mapper/VolGroup00-LogVol00 81269424 66551756 13878808 83% /
Sweet, touch over 3GB