Friday, August 19, 2011

How to get your full disc space back on ext filesystems

You may have already wondered why you can't use the full disc space on an ext2/3/4 partition? You already seen something like this, where the used and available blocks don't fit the number of blocks on the device/partition:
Filesystem 1K-blocks   Used    Available Use%  Mounted on
/dev/sdc1   15391664  38184   14571608      1%  /mnt
The reason is: if you create an ext filesystem (no matter if with mkfs or YaST), 5 % of the filesystem get reserved for the super-user to allow e.g. root daemons to continue to write to the partition after unprivileged processes stopped because the partition is full.
While this perfectly make sense on system partitions as '/', it makes no sense on data partitions or external media (in the most cases). By this you get e.g. on an external 2TB/1.8TiB drive 100GByte/~92GiB, which you can't use as normal user. But you can get this space back. Either you set the number of reserved blocks to zero when you create the file system:
mkfs -t ext4 -m 0 /dev/sdc1
or you do it later:
# make sure partition is unmounted
umount /mnt
tune2fs -m 0 /dev/sdc1
On a LUKS encrypted  you have to do this:
# on a LUKS device
umount /media/disk
tune2fs -m 0 /dev/mapper/udisks-luks-uuid-X
 You should see this output:
tune2fs 1.41.14 (22-Dec-2010)
Setting reserved blocks percentage to 0% (0 blocks)
 And if you mount the device again, you can see with df that you have the full space available:
 Filesystem 1K-blocks   Used    Available Use%  Mounted on
 /dev/sdc1   15391664  38184   15353480      1%  /mnt

Wednesday, August 17, 2011

Update for extundelete

Today I've submitted a new extundelete package to my repo with following fixes:
  • added man(8) page to the package
  • fixed --help output to print also info about --restore-directory
  • added --dump-names option to search for - and print the full name of - deleted and (potentially fully) recoverable files on a given partition 
Feel free to test and report problems back. The package is now also part of the filesystems project.

Tuesday, August 09, 2011

How to undelete files from ext3/ext4

Sometimes, especially on the command line, it happens that you delete a file or directory you didn't really plan to delete. A second after hit enter you realize what you have done, maybe you are fast enough to stop the deletion process and save some files, but in the most cases it's already to late, at least for some files.  If you have no or a too old backup you're screwed. 
If you use ext3/ext4 you may be able to recover the file with ext3grep or extundelete with information from the file system journal if the content of the file wasn't already overwritten by new data. 
The first step should be to stop all writing processes on the related partition and unmount that partition as soon as possible. Now you have the choice: if your partition uses ext4 you have to use extundelete, if it's ext3 you can use also ext3grep. Personally, I prefer extundelete, since it supports both file systems and seems on one hand much faster to me than ext3grep and it's also easier to use on the other hand. Due to that, the following examples are for extundelete (you can find a ext3grep How-To here).
If you know the path and the name of the file (let's assume it's /home/tux/cv.tex and /dev/sda4 is mounted to /home) you deleted, switch to root and go to a partition with enough free space to store the deleted files. Then:
# extundelete need the relative file path 
me:/tmp # extundelete --restore-file tux/cv.tex /dev/sda4
As soon as extundelete finished, you'll find the recovered file in /tmp/RECOVERED_FILES/tux/ .
If you deleted more than one file in a directory or a directory itself, you can use --restore-directory :
# extundelete need the relative dir path 
me:/tmp # extundelete --restore-directory tux/Documents/tex/ /dev/sda4
There are some more useful options as --restore-all , --restore-files, --after 'dtime' or --before 'dtime', but in the most cases the two examples above should be enough. You can find both tools in my buildservice repository.

Updated xinput_calibrator packages

Today I found some time to update the xinput_calibrator packages in my buildservice repository. The new version is 0.7.5. And since someone asked in my last post for 11.4 rpms, I've activated the build also for openSUSE 11.4. 
Feel free to test and report back if you have any trouble with the updated version.