weird: directory permissions change inadvertently

stabu · 12-01-2006, 05:25 AM

Just recently I have a weird problem with some of my harddisk partitions, some are in vfat and others ext2 and ext3.

Usually I boot up and login as root to do some heavy file shifting, which of course means write permissions as I'm deleting some stuff.

In the beginning it's fine (I'm in as root after all). But then I go into midnight commander for something and all of a sudden I lose write (and therefore delete) permissions to one or two of the directories, some of which are rather full, I should add.

When I "ls -l" these directories they have chmod 755 and stuff though I set to chmod 777 to make sure but still no joy.

Now, I've never understood umask, but I feel that some sort of global variable is being changed. Or else it's that these directories are too full, because this unusual dynamic effect doesn't happen with the emptier directories.

Anybody any clues? Cheers.

dracolich · 12-02-2006, 02:05 PM

If you're in the vfat directories then, yes, they can be full to a maximum number of objects for the root of the drive. eg. If /mnt/vfat is the root of one fat32 drive then it can only hold x number of objects before it's "full" regardless of how much disk space is left. I forget the exact number but x is somewhere around 128.

Ext2 and 3 are different. I don't know what the limit is for them as I've never run into it.

stabu · 12-03-2006, 06:06 AM

Is that right about vfat? That's a pain. I reckon there's a bucnh of people who use vfat as a Windows/Linux harddisk share on dualboot machines and don't know about that limit. Gonna check that up: not cos I don't believe you but to find out how to get around it.

dracolich · 12-03-2006, 12:20 PM

I just found the numbers myself, and more detail than I had found in the past.

Quote:

An interesting side effect results from the way VFAT stores long filenames. When you create a long filename with VFAT, it uses one directory entry for the DOS alias and another entry for each 13 characters of the long filename. In theory, a single long filename could occupy up to 21 directory entries. The root directory has a limit of 512 files, but if you were to use the maximum-length long filenames in the root directory, you could cut this limit to a mere 24 files. Therefore, you should use long filenames very sparingly in the root directory. Other directories aren't affected by this limit.

from

http://www.microsoft.com/technet/arc...eploy/fat.mspx

The solution is to make some subdirectories.