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Subject : Re: LUG: Another Ubuntu Puzzle

From : Brian Pike <bapike@gmail.[redacted]>

Date : Wed, 16 Nov 2005 09:53:25 -0500

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Remember that FAT32 is a filesystem from the single-user, DOS era.  Files don't have the same metadata that a file on any modern Unix filesystem would have.  Wikipedia says that the attributes are only read-only, hidden, system, archive, and volume name (with no stored permissions).  If you ask chmod to set the execute bit on a file in a FAT32 system, I'm honestly not sure what it'll do since there's no execute attribute to set.  Note also that every file on that filesystem will be owned by a single user and group.

Second, check the options set for these filesystems in /etc/fstab, especially uid, gid, umask, dmask, fmask, and noexec (see mount(8) and search for 'fat').  If there's a umask set on the entire filesystem, then you may be seeing odd behaviors.

I performed your 'touch test; chmod 722 test' operation, and apparently the permissions are set to 700 only temporarily.  Upon remounting the filesystem, the permissions are 755.  I'm not sure why that sort of surprising behavior is intended.

Hope that helps,
-Brian

On 11/15/05, Ken Whichard < wwhichard@nc.rr.[redacted] > wrote:
As I've said before - lots of Solaris SA experience but Ubuntu is confusing the old man!

Have added a second hard disk to the box running Ubuntu.  Partitioned it into two partitions fat32.  I think I have mounted them since I can cd to each and add files from within Ubuntu.

When I try to ftp from another box, I can list the files on the partitions but cannot write to the partitions.

Sure enough the permissions are 755 on each of them.  No problem, I sudo chmod 777 - should fix the problem, nope, now they are 744!  OK, I'll fix that - set a root password, su to root and run chmod again - same result.  It seems I cannot set either partition's permissions to include write for group or world.

Even this -- I touch test on one of the partitions, then chmod 722 test and the permissions are -rwx------ !  Go figure

OK - what the heck am I doing wrong?

A puzzled class of '61 grad!

Ken Whichard

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