I decided to give Wesnoth a try yesterday, so i went into app manager and checked how much space it would take up on my internal memory. (I've had to reflash from accidentally running out of space before. ) App manager told me the wesnoth install package (deb, i guess?) is 26 MB, and it would take about 60 MB to install. so, i cleaned up my internal memory, wiping out a couple of themes and a couple of games that i never used (sorry, nuvoclear; sorry, supertux), and File Manager told me i had about 76 MB free.

after installing wesnoth, i immediately opened File Manager again and checked my free space: 64 MB. whah? the entire wesnoth application, fully installed appears to take up less than the size of the deb (?), as reported by app manager. that doesn't make sense. what's the deal?

then, i ran wesnoth and there was no text in the dialog boxes and i didn't feel like troubleshooting it (maybe another day), so i uninstalled. Now File Manager reports that I have about 66 MB free. wtf? i want that space back. what did wesnoth leave behind? and now i'm wondering how much of my internal memory is being occupied by crap left behind by apps that i uninstalled in the past. it just might drive me crazy.

so, which numbers are accurate and which are inaccurate? what am i missing here?

well, the tablet uses an compressed filesystem (jffs2) which makes files smaller. The bit that shows the installed size of a deb is nothing special, it is just a number in the deb file which is calculated on the computer that the deb was made from on an uncompressed filesystem.

Re second question, you may want to look at:
http://www.internettablettalk.com/fo...ight=deborphan
http://www.internettablettalk.com/fo...ight=deborphan

I thought the application author had to manually fill in that field in the control file? In which case it's not calculated on-the-fly so it's anyone's guess

That's if the package is made by hand (ar, dpkg-deb --build etc) and not using debhelper like it should be (Installed-Size is filled out when dh_gencontrol is run as part of debian/rules).

To calculate the installed-size manually (for those diehards that do still make packaged by hand) : "ar x foo.deb data.tar.gz ; mkdir tmp ; tar -C tmp -xzf data.tar.gz ; du -sb tmp ; rm -rf rmp data.tar.gz "

a compressed file system! that's it. that's the piece of the puzzle i was missing. and as far as cleanup goes, I'll consider localepurge (should be "local" purge?), deborphan, cruft, and the script given here. so, things i've learned today are...

1) I can trust File Manager to report free space accurately.

2) Application Manager can be inaccurate when reporting installed-size if the author didn't use debhelper or do a manual calculation. But even assuming that the author did one of those, the installed-size given in app manager can be misleading to newbies like me.

Follow-up: Can I use the installed-size given in app manager ("fake" installed-size) to estimate how much space an app will actually use ("actual" installed size)? it's suggested here that jffs2 generally has a 2:1 compression ratio, but wesnoth only used about 1/5 of what app manager specified. i'm sure it depends on the content. perhaps i'll just divide by 2 to be safe....