Cannot change permissions on a mountable drive

[Hong F Du]

Hi All,

I have a dos formatted drive /mnt/dosE, its permission is 761. When it is not mount yet,  I can change its mode to 771. When I mount it, its permission is automatically changed back to 761. Once the drive is mounted, I cannot change its permission no matter what I try.

What is going on here? How should I make the permission change?

Thank you in advanced

feng

[Tim Walberg]

On 07/19/2000 14:28 -0400, Hong F Du wrote:
>> Hi All,
>>
>> I have a dos formatted drive /mnt/dosE, its permission is 761. When it
>> is not mount yet, I can change its mode to 771. When I mount it, its
>> permission is automatically changed back to 761. Once the drive is
>> mounted, I cannot change its permission no matter what I try.
>>

When the drive is not mounted, the chmod affects only the directory
on which the drive will be mounted. Once the drive is mounted, the
root inode of that filesystem overlays the directory (so you can't
get to the directory any more until the drive is unmounted), so chmod
would then affect that inode, and not the directory. Why you can't
change the mode on the filesystem's root inode, though I can't
say - are you mounting it read-only? Is it NTFS, which (usually)
can't be mounted read-write? A cdrom? A FAT filesystem which doesn't
relate directly to the Unix permission triad? Need more information
to analyze any further...

tw

>> What is going on here? How should I make the permission change?
>>
>> Thank you in advanced
>>
>> feng

End of included message

--
+--------------------------+------------------------------+
| Tim Walberg | tewa...@mediaone.net |
| 828 Marshall Ct. | www.concentric.net/~twalberg |
| Palatine, IL 60074 | |
+--------------------------+------------------------------+

[Hong F Du]

The /mnt/dosE is a fat16 file system which is on a ide hard drive from my
dual-boot NT/Linux system. It is setup as msdos type with auto translation mode
when mounted. As a root, I can rwx the mounted /mnt/dosE. Now I want it to be read
and writable for USERS group too, that makes problem appear.

feng

Tim Walberg wrote:

> ------------------------------------------------------------------------
> Part 1.2Type: application/pgp-signature

[Hong F Du]

I got the following error messages when I used gnome-liunxconf and click on a source drive of
Access local drive under File system. In addition, I can only see only one device drive on the
Partition scroll down window under the Volume specification even though there are actually
over six partitions shown under Local volume.

Error message from remadmin:
Error message from remadmin:Gtk-CRITICAL **: file gtkcombo.c: line 817
(gtk_combo_set_popdown_strings): assertion 'strings !=NULL' failed.
Error message from remadmin:
Error message from remadmin:Gtk-CRITICAL **: file gtkwidget.c: line 1584 (gtk_widget_map):
assertion `GTK_WIDGET_VISIBLE (widget) == TRUE' failed

What does it mean? Would this cause all my problems?

feng

Tim Walberg wrote:

> You can accomplish this using the uid, gid, and umask options
> of mount. See the mount manpage (under the options for fat
> section) for more details.
>
> tw

[Hong F Du]

My problem still persists. I read the manpages of mount and umount and some books too.
Then I checked the file /etc/fstab, the entry I am having problem with is:

/dev/hda6 /mnt/dosE msdos user,exec,dev,suid,rw,conv=auto,uid=0,gid=100
1 1

I am trying to understand part of this line, Can some one please tell me what this

user,exec,dev,suid,rw,conv=auto,uid=0,gid=100 1 1

means, specially exec,dev, suid ,uid=0? What other options do I have? What is the
default setting for a FAT16 file system?

Thank you

feng

[Larry Collier]

The meanings are (from mount(8) and fstab(5) man pages):

user - allow any user to mount this.
exec - permit execution of binaries from this drive.
dev - interpret character or block special devices found on the file
system.
suid - allow suid and sgid bits active, i.e. executables can be run suid and
sgid.
rw - mount file system with read and write.

conv=auto - convert carriage return/linefeed pairs to/from newline character
automatically based on well known file extensions
uid=0 - mount all files with a uid of zero (that's root)
gid=100 - mount all files with group id set to 100 (usually this is the
"users" group

I don't see anything wrong with the above but I wouldn't use suid, uid=, or
gid=. And I'm not sure what effect "dev" would have on a FAT16 partition.

I use noauto and user only. The defaults for other capabilities are
generally safe. "Exec"uting msdos binaries under Linux isn't something I'd
normally try. Mounting read/write is the default so an explicit statement
isn't needed. Allowing everything on the drive to be executed suid is not a
good idea at all.

Hope this helps,

la...@medease.com
lcol...@ak.net