I rooted my phone for one reason: The available space for apps was constantly shrinking! The updates in the Google Play store failed with the error “not enough space available” and I had to de-install apps in order to update or install new apps.
Programs could eat up the space with their user data, so I often cleared the data of e.g. Firefox, but the suspect remained that the total space is shrinking, because the tool “DiskUsage” was showing a big amount of “System Data”, but without root permissions there is no way of tracking it any further.
Once rooted the culprit was easy to see: /data/lost+found was containing like 600MB. On Linux (or ext3/ext4 file systems to be more specific), the lost+found is a system folder where fragments of files go which don’t belong to a file and have been found on a fsck (file system check).
As it is pretty unlikely to recover some data from it you can usually delete the content. It’s a bad sign that there are files in it, the reason could be sudden reboots or system crashes, but there is little you can do. This is the user data partition and what if the Facebook app is missing 4096 bytes in the middle of a database or so?
You can probably delete it on the device using a root file explorer. I did it using adb. On Ubuntu it’s easy:
# install the adb tool $ sudo apt-get install android-tools-adb # open a shell on the device $ adb shell # you should see a prompt like: ~ $ # become root (be careful now!) ~ $ su root@android:/ # # go to /data root@android:/ # cd /data/lost+found # verify root@android:/data/lost+found # pwd /data/lost+found root@android:/data/lost+found # ls -l [.. directory ..] # delete. this is a recursive delete, be extra careful! root@android:/data/lost+found # rm -rf *
Log out with “Ctrl-D” two times. If you want, you can check the available space with “df -h” while in the Android shell. You should have more free space than before now.
There are other folders consuming some space, e.g. /data/log, but I left them untouched for now to not risk anything. It would probably be save to clean that up, but it wasn’t taking too much space.