Stefan has provided a wealth of infomation to this community and I'm pleased to offer another of his contributions.

Some additional safety checks before
upgrading to / installing OpenPMA v0.1.1 (and higher)
or 
How to check for filesystem errors that you can't see / find under Windows

As many people with a little more than general interest in the structure of the Archos PMA430 have already noticed, the most important files for the OS and applications are the two aimage.img and progfs.img files that can be found in the \System directory (if you look via Windows explorer) or - if you see it from the PMA's side - in /media/System.

While aimage.img contains the OS, the progfs.img (usually with a size of 64 MB) holds many of the applications Archos supplied or the user has later installed. Progfs.img will be mounted during boot and used while the Archos PMA / Qtopia is running. The internal filestructure of the progfs.img is called ext2 (see Wikipedia for further details). Because of this structure, it is impossible to check for filesystem errors from Windows via an USB mounted PMA. (Okay, there are ext2 drivers for Windows available, but that's another story.)

Because of the faulty implementation of the harddisk driver under Archos' OS v14-2 (and previous), the chance of creating filesystem inconsistencies within this progfs.img is there, even without doing (using) anything special.

So it is recommended to do a filecheck for errors within progfs.img. This can be done from time to time, but for sure BEFORE converting (upgrading) to another OS implementation like OpenPMA. Since openPMA v0.1.1 the harddisk driver is flawless, and these errors shall be a thing of the past. The following lines shall give a hint  how the procedure works and what you have to check. Since openPMA this is possible from within the PMA using commands in the terminal. Under the original Archos OS this was not possible without using e.g. a separate Linux machine.

Time involved: An hour or less.
Outcome: You're sure you don't have file system errors anymore.

As usual, take your time and read thru the whole procedure first.

Requirements:

• openPMA v0.1.1 (or higher) installed
• a working USB connection to your PC
• access to a few backups you've done months ago, one or two are enough, but you might need more later ...

I've make this description for users who have a Windows PC with an USB port where they connect the PMA to. If you have a different setup (e.g. a Linux PC), I'm sure you either don't need detailed instructions or you can translate it into your system commands. 

LONG VERSION:

Preparation:

PMA: = drive letter of your PMA.

Make a backup of your PMA if you haven't done so recently. Please do NOT do this while the system is running. Shutdown (via Qtopia "Shutdown" software button) first, connect to an USB port, and switch PMA on. If you have WinXP, open "start" and use run to enter "cmd" there (you might know how to open a command window already, I assume). Now type "chckdsk PMA:" first.

Any errors? If yes, continue at (a). If no, continue at (b).

(a) If yes...

• Make a backup of ALL files to your PC first.
• Type "chckdsk PMA: /f" now. Errors would be corrected, don't transform lost clusters into files if asked.
• Type "chckdsk PMA:" again. No errors left? Fine. If not, you have to check for defective harddisk sectors by doing "chckdsk PMA: /r" until "chckdsk PMA:" shows no remaining errors.

(b) If no...

Fine! If everything's fine (and/or repaired), you can now copy the files to your PC - into a new directory, please. I would call this procedure "cold boot USB copy". You can copy all files, if you want. I would feel safer in this case, but we're only messing with /media/System/progfs.img at the moment, so this would be enough to copy if you have just copied everything else a couple of hours or a day ago. You can copy via Windows explorer if you want.

Everything's (or just /System/progfs.img) copied?

• Run "cmd" on PC again to get a command window.
• Switch to your PMA's drive letter by typing PMA: <enter>
• Switch to /System folder on your PMA by typing:
  
  cd /System <enter>
  
  
• Make a copy of your profs.img file on the PMA itself (into the same System folder) by typing:
  
  copy progfs.img progfsc.img <enter>
  
  
  (The copy will get the name "progfsc.img"). It takes a minute or two. You can also use the Windows explorer to do this - or any other copy program - but make sure the copy is named "progfsc.img" and can be found in the same /System folder.
  
  Close the command window when the copy is done - you'll see no reply. Check that the red hardisk activity light on the PMA is quiet now.
  
  
• Safely disconnect the PMA from the PC via the Windows' taskbar button for (USB) devices.
• Let the PMA continue to boot. When done, open the terminal / command line on the PMA.
• Type:
  cd /media/System
  
  
• Type:
  e2fsck -f progfsc.img
  
  
• You shall see:
  
  e2fsck 1.27 (21-Mar-2005) [depending or your openPMA
  version, there might be a diff. version and/or date]
  { ... You MIGHT see some short journal message here ... }
  Pass 1: Checking inodes ...
  Pass 2: Checking directory structure
  Pass 3: Checking directory connectivity
  Pass 4: Checking reference counts
  Pass 5: Checking group ...
  Progfsc.img xxxx/yyyyy files (x.y% non-contin...), xxxx/yyyy blocks
  
  

... IF (!!!) everything's fine. In this case, you're on the sunny side and out of testing.

IF you will see any error messages, asking you for correcting / repairing anything found strange, PLEASE answer with an equivalent to NO - mostly it's a number to type for that option, e.g. option 2 or 3.

In the case of error messages, we now have the option to correct these (which didn't work in my case), to live with them (which I won't recommend) or to find somewhere in your backups a progfs.img that doesn't show these errors.

Explanation needed here:
The errors might have happened while using ArchosOS or openPMA v0.1 and prob. some evil program terminated or was blocked so you had to reboot.

There was no way to do a similar command to the DOS "chkdsk" on this ext2 progfs.img previously and even on openPMA 0.1.1 it's still a little complicated. The e2fsck is a linux command that can check filesystems created inside an image file for errors. It's possible to try it while the image is open and/or the filesystem is running, but the results shown might be irritating because of opened files. So don't try it first on progfs.img itself, only on a copy made while there was no access to the filesystem / image (that why we did the "cold boot USB copy").

When you try to correct the errors e2fsck has found, you might end up with a progfs(c).img that don't work correctly anymore. So always have a backup of progfs.img by hand that runs okay, even with or without file system errors inside, so you could copy it back to have access to your options / settings etc.

IF you seen any errors while checking as mentioned previously, you can now try if a corrected image would run.

Let e2fsck -f progfsc.img run again and try to answer to the appropriate options to correct any errors found. A little sooner or later you're done, so shutdown (via reboot software button). Do a "cold boot USB copy" again, now copying the corrected progfsc.img to progfs.img.

Overwrite the normal progfs.img IF you have a copy of that on your PC (if not, make a copy NOW). You can again copy in a cmd window on your PC:

copy progfsc.img progfs.img <enter>

(Reply with "yes" when you're asked to overwrite) When finished copying, disconnect the USB device safely and let the PMA boot. When the PMA has restarted, try a couple of programs (best the ones you've used often or you don't like because they stopped or broke often). If they run okay, fine.

Try testing this progfs.img for a couple of days. If you want later to check if it's still okay without filesystem errors inside, do the same procedure again: shutdown, connect to USB, boot, copy /System/progfs.img to /System/progfsc.img, and let "e2fsck -f /media/System/progfsc.img" run. Even then, it's recommend to do it in intervals so you KNOW there's nothing messy inside. 

SHORT VERSION:

• Have openPMA 0.1.1 on your PMA.
• Make at least a copy of your PMA's /System/progfs.img to your PC directly after shutdown/switch-on via the USB connection. Make also a copy of /System/progfs.img to /System/progfsc.img - on the PMA itself. Disconnect safely, when the PMA is available again, use the terminal and type:
  
  cd /media/System e2fsck -f progfsc.img
  
  
• If you only see: Pass 1 to Pass 5 without any errors noted, you're fine. If you see any errors, try to correct these using the appr.
  option(s) when asked.
• After correction, shutdown the PMA.
• Connect via USB, switch PMA on and copy(overwrite) /System/progfsc.img to /System/progfs.img.
• Disconnect safely, let the PMA boot and try if everything's working okay for a couple of days. If not, you'll have to find an older progfs.img (remember to copy this to progfsc.img before trying to correct) that you can either be corrected well or that don't show any errors. You might have to reinstall some newer programs when switching back to an older progfs.img.  

In my case, many progfs.img files from my backups I tried to correct inside (via e2fsck) did NOT work later on. I had to go back to a progfs.img dated January 2006 that was still correct inside and use this. This required that I reinstall all programs since then and check all settings for the correct values. A lot of work, but worth the effort so I know now everything's fine, even inside.

BTW, the size of the progfs.img didn't matter. Normally it's 64 MB, but even a 512 MB one (enlarged via Bubu's script) runs fine.

Eratta:

• You should also do an "e2fsck -f /media/System/progfs.img" (on the original image while it's mounted and in use) from time to time (best directly after a reboot). If it doesn't show errors, fine. IF there are errors, do NOT try to correct these now while progfs.img is mounted. Do the copy procedure as described above and do the corrections on the copied image. If successfully corrected, copy it back over the original image. But make a copy first.
  
  
• Normally, the Linux system has a maximum mount count for each filesystem set, and if it's over that maximum, an automatic filesystem check (fsck) will be forced during boot. You can see a similar message asking for repair during the first boot after you have prob. upgrading to openPMA.
  
  Example: ["dmesg" issued in the terminal] - shows:
  EXT_-fs warning: maximal mount count reached, running e2fsck is recommended ...
  

You can set this max. mount count with the command "tune2fs", but this command can also be used to check the maximum count.

Example:

tune2fs -l /media/System/progfs.img (issued in the terminal) reported on my PMA:

Mount count: 95
Maximum Mount Count: 34
Last checked: Sept 17 2006
Check interval: ... (6 months)

As you can see, it's time for another "e2fsck" on progfs.img here.

The mount count settings are the cause why you should use e2fsck with option "-f" (for "-force") here. Without -f, it only checks the file if the mount count is over the maximum.