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Re: [vox-tech] good reference source for fstab permissions
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Re: [vox-tech] good reference source for fstab permissions



On 2003.07.03 09:18, Jonathan Stickel wrote:
Donald Childs wrote:
Thanks for all the assistance . I'm able to write to the vfat partition
now, using:

/dev/hdf4 /mnt/fat vfat user,rw,uid=[user],gid=[workgroup] 0 0

but will go back and add the showexec attribute.
This is different from what I use for my fat32 partition(s). I have in my fstab:

/dev/hda5 /Documents vfat defaults,quiet,umask=0000 0 0

I'd like to learn a little more about these mount options, if someone cares to enlighten me:

My method mounts on bootup, allows all users read/write permission, and quiets failed attempts to change file ownership/permissions. Reading a little of the man page, I get the impression that "umask=0000" and "quiet" essentially overrides the "suid" implied by using the "default" option. Is this about right?
It appears that this umask is in agreement with the suid option. Setting umask=7000 would seem to be in disagreement the suid option but would seem to be in consonance with the nosuid option.

It seems to me Donald's fstab entry only gives read/write permission to [user] and [workgroup]. Also, it is not clear to me whether the partition would mount on startup or with "mount -a" ("auto" option is not specified). But I can see the ownership/permission problems of fat is solved by assigning the entire partition to just one user. How am I here?
I believe it follows the default umask of 022, so only the owner can write, but everyone else can read and execute. By saying user, anybody can mount and unmount the partition (I'd bet that this isn't Donald's intended effect). It appears that it is mounted automatically (like my vfat partition).

My vfat partition:
/dev/hda6 /home/bloom/mydocs vfat umask=073,uid=1000,gid=1000,
noexec,showexec 0 0

I am also curious about the "showexec" option. If I used it, would it make "quiet" unnecessary?
No. Showexec just sets the default permissions differently. If you list your vfat drive now, then you will notice that all directories and *all* files are rwxrwxrwx. You would probably prefer to have your files rw-rw-rw- (I found the execute bits especially annoying when working with xftree, and when burning CD-ROMs) This is what showexec does.

Kernel 2.5.43 and later (according to mount(8)) replace this with fmask and dmask which set umasks for files and directories, respectively. I haven't used 2.5.x kernels, so I don't know for sure whether showexec will be removed, or merely deprecated. It took me a while to discover showexec because I had been hoping to find something more like fmask and dmask to begin with.

Quiet prevents chmods and chowns from returning errors. It can be used with showexec the only difference is the exact set of permissions that cannot be changed.

Also note that the write bits can actually be changed permenantly (at least without the quiet option) if all three are the same they affect the native FAT read-only bit that can also be set from and has an effect in Windows (if they're not all the same, see your kernel source to see who wins). And I found that (again, without quiet) other file permissions (like execute) can be changed temporarly and Linux will remember the permissions until the operations involving file dates would fail though (I don't know whether they do with quiet).

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