free space disappearing on live-usb

[oakhunter]

Binary package hint: usb-creator

I run Ubuntu 8.10 live-usb created with usb-creator.

Everything went well until I updated the packages several times with update manager. Suddenly I noticed that a free space on the file system dramatically decreased.

I used all the recomendations from "Cleaning up a Ubuntu GNU/Linux system" (http://www.ubuntugeek.com/cleaning-up-all-unnecessary-junk-files-in-ubuntu.html) and run "Ubucleaner" (http://www.ubuntips.com.ar/2007/12/12/ubucleaner-10-limpia-tu-ubuntu/) script but with no luck. Then I uninstalled Mono, GIMP, games and few other things; removed all localization stuff. But nothing helped me to reclaim free space. (I've already done all the actions with apt cleans, removes, orphan packages, locales, browser caches, logs, etc)

Finally, it came to the point, where 0 bytes of free space left. However, that fact don't prevent me to copy ~100MB of new files to the file system (I wonder how it could be possible).

Every time I try to free up any disk space it will disappear instantly so i have 0 bytes of free space.

Now, it seems, that persistence works only partially, and I can't update system packages with update manager (because of the lack of free space). Whole system is unstable.

I've attached results from "df" command and screenshot from "Disk usage analyzer".

[oakhunter (oakhunter)]

Here's topics from ubuntuforums.org with similar problem:

http://ubuntuforums.org/showthread.php?t=984276
http://tennessee.ubuntuforums.com/showthread.php?t=980794
http://ubuntuforums.org/showthread.php?t=994044 (mine one)

[oakhunter (oakhunter)]

I've figured-out the root of the problem. It's not a true bug, it's a «feature», resulted from the way usb-creator works.

Architecture assumes using SquashFS (http://en.wikipedia.org/wiki/SquashFS) together with UnionFS (http://en.wikipedia.org/wiki/UnionFS) to create semi-writable compressed file system (explanation of the technique: http://tldp.org/HOWTO/SquashFS-HOWTO/creatingandusing.html#sqwrite). As such, copy on write (http://en.wikipedia.org/wiki/Copy-on-write) used when any file from squashed file system must be rewritten. No wonder this doubles space consumption every time you modify (or just touch) a file from original installation. Also, there's no way to delete these files.

Two file storages are mounted through loop devices (http://en.wikipedia.org/wiki/Loop_device) (/dev/loop0, /dev/loop1) so you can see all newly created additional files by mounting /dev/loop1.

Hence, it seems that installations made with usb-creator are good for small flash drives (because of the SquashFS usage), but running update manager with SquashFS is not such a brilliant idea (because this may require much more space comparing with direct installation, and can create problems resulted from inability to delete files).

So if you want to create installation to update it later, it's better to avoid using usb-creator and perform direct setup to flash-drive.

As for usb-creator, maybe we should provide a choice to avoid SquashFS usage and to install the whole system on a writable destination.

[komputes (komputes)]

Looking at your df attachment this seems to be related to Bug #305451. If you can confirm this please mark as duplicate.

[Victor Vargas (kamus)]

We are closing this bug report because it lacks the information we need to investigate the problem, as described in the previous comments. Please reopen it if you can give us the missing information, and don't hesitate to submit bug reports in the future. To reopen the bug report you can click on the current status, under the Status column, and change the Status back to "New". Thanks again!