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Old 04-09-2012, 07:59 PM
Mark Knecht
 
Default User can mount/umount but not write to top the new drive

Hi,
This has long been a sort of hack area of me in terms of sys admin
at home - giving a user account access to the top of a new external
drive. I'd like to learn to do this right. Maybe someone can set me
straight about what root needs to do to make this work.

OK, so as root I partition & format the USB drive to get it ready,
and then I modify fstab with the following addition:

c2stable ~ # cat /etc/fstab | grep VideoLib
LABEL=VideoLib /mnt/VideoLib ext3
auto,rw,users 0 0
c2stable ~ #

Having done that, as well as making the /mnt/VideoLib mount point,
my user account can now mount & umount the drive:

mark@c2stable ~ $ mount /mnt/VideoLib/
mark@c2stable ~ $ df -h | grep VideoLib
/dev/sdf1 458G 199M 435G 1% /mnt/VideoLib
mark@c2stable ~ $ umount /mnt/VideoLib/
mark@c2stable ~ $ df -h | grep VideoLib
mark@c2stable ~ $

The problem is that at this point my user account cannot create a
new directory on that drive:

mark@c2stable ~ $ mount /mnt/VideoLib/
mark@c2stable ~ $ df -h | grep VideoLib
/dev/sdf1 458G 199M 435G 1% /mnt/VideoLib
mark@c2stable ~ $ mkdir /mnt/VideoLib/Video
mkdir: cannot create directory `/mnt/VideoLib/Video': Permission denied
mark@c2stable ~ $

In the past I've gotten around this by having root mount the drive
and then change ownership to mark:users once it's mounted. Linux
remembers I've done that once and no longer requires me to do anything
else as root.

Is that truly required or is there a way to give the user access to
the top of the new mount point without roots' involvement?

Thanks,
Mark
 
Old 04-09-2012, 08:38 PM
Canek Peláez Valdés
 
Default User can mount/umount but not write to top the new drive

On Mon, Apr 9, 2012 at 2:59 PM, Mark Knecht <markknecht@gmail.com> wrote:
> Hi,
> * This has long been a sort of hack area of me in terms of sys admin
> at home - giving a user account access to the top of a new external
> drive. I'd like to learn to do this right. Maybe someone can set me
> straight about what root needs to do to make this work.
>
> * OK, so as root I partition & format the USB drive to get it ready,
> and then I modify fstab with the following addition:
>
> c2stable ~ # cat /etc/fstab | grep VideoLib
> LABEL=VideoLib * * * * */mnt/VideoLib * * * * * ext3
> auto,rw,users 0 0
> c2stable ~ #
>
> * Having done that, as well as making the /mnt/VideoLib mount point,
> my user account can now mount & umount the drive:
>
> mark@c2stable ~ $ mount /mnt/VideoLib/
> mark@c2stable ~ $ df -h | grep VideoLib
> /dev/sdf1 * * * 458G *199M *435G * 1% /mnt/VideoLib
> mark@c2stable ~ $ umount /mnt/VideoLib/
> mark@c2stable ~ $ df -h | grep VideoLib
> mark@c2stable ~ $
>
> * The problem is that at this point my user account cannot create a
> new directory on that drive:
>
> mark@c2stable ~ $ mount /mnt/VideoLib/
> mark@c2stable ~ $ df -h | grep VideoLib
> /dev/sdf1 * * * 458G *199M *435G * 1% /mnt/VideoLib
> mark@c2stable ~ $ mkdir /mnt/VideoLib/Video
> mkdir: cannot create directory `/mnt/VideoLib/Video': Permission denied
> mark@c2stable ~ $
>
> * In the past I've gotten around this by having root mount the drive
> and then change ownership to mark:users once it's mounted. Linux
> remembers I've done that once and no longer requires me to do anything
> else as root.
>
> * Is that truly required or is there a way to give the user access to
> the top of the new mount point without roots' involvement?

Have you tried:

# cat /etc/fstab | grep VideoLib
LABEL=VideoLib * * * * */mnt/VideoLib * * * * * ext3
auto,rw,users,uid=X,gid=Y 0 0

where X is mark's user id, and Y is users' group id?

On the other hand, do you use a desktop environment? Because GNOME
does everything you want for you, and I suppose KDE does the same.

Regards.
--
Canek Peláez Valdés
Posgrado en Ciencia e Ingeniería de la Computación
Universidad Nacional Autónoma de México
 
Old 04-09-2012, 08:48 PM
Neil Bothwick
 
Default User can mount/umount but not write to top the new drive

On Mon, 9 Apr 2012 12:59:31 -0700, Mark Knecht wrote:

> In the past I've gotten around this by having root mount the drive
> and then change ownership to mark:users once it's mounted. Linux
> remembers I've done that once and no longer requires me to do anything
> else as root.

That's right, the root of the filesystem is now owned by mark.

> Is that truly required or is there a way to give the user access to
> the top of the new mount point without roots' involvement?

Not with a Linux filesystem[1][2], because the filesystem is owned by
root, so only root can change that.

[1] This isn't strictly true as you can do it with ACLs, but that is far
more complex than simply chowning the root of the filesystem if that is
all you need.

[2] With Windows filesystem, there are mount options to set the default
ownership, but that is a workaround for the differences between Linux and
Windows metadata.


--
Neil Bothwick

TROI : What am I sensing?? I'm sensing INCOMPETENCE, you pretentious
bald pseudo-French dickweed!
 
Old 04-09-2012, 09:22 PM
Mark Knecht
 
Default User can mount/umount but not write to top the new drive

On Mon, Apr 9, 2012 at 1:38 PM, Canek Peláez Valdés <caneko@gmail.com> wrote:
> On Mon, Apr 9, 2012 at 2:59 PM, Mark Knecht <markknecht@gmail.com> wrote:
>> Hi,
>> * This has long been a sort of hack area of me in terms of sys admin
>> at home - giving a user account access to the top of a new external
>> drive. I'd like to learn to do this right. Maybe someone can set me
>> straight about what root needs to do to make this work.
>>
>> * OK, so as root I partition & format the USB drive to get it ready,
>> and then I modify fstab with the following addition:
>>
>> c2stable ~ # cat /etc/fstab | grep VideoLib
>> LABEL=VideoLib * * * * */mnt/VideoLib * * * * * ext3
>> auto,rw,users 0 0
>> c2stable ~ #
>>
>> * Having done that, as well as making the /mnt/VideoLib mount point,
>> my user account can now mount & umount the drive:
>>
>> mark@c2stable ~ $ mount /mnt/VideoLib/
>> mark@c2stable ~ $ df -h | grep VideoLib
>> /dev/sdf1 * * * 458G *199M *435G * 1% /mnt/VideoLib
>> mark@c2stable ~ $ umount /mnt/VideoLib/
>> mark@c2stable ~ $ df -h | grep VideoLib
>> mark@c2stable ~ $
>>
>> * The problem is that at this point my user account cannot create a
>> new directory on that drive:
>>
>> mark@c2stable ~ $ mount /mnt/VideoLib/
>> mark@c2stable ~ $ df -h | grep VideoLib
>> /dev/sdf1 * * * 458G *199M *435G * 1% /mnt/VideoLib
>> mark@c2stable ~ $ mkdir /mnt/VideoLib/Video
>> mkdir: cannot create directory `/mnt/VideoLib/Video': Permission denied
>> mark@c2stable ~ $
>>
>> * In the past I've gotten around this by having root mount the drive
>> and then change ownership to mark:users once it's mounted. Linux
>> remembers I've done that once and no longer requires me to do anything
>> else as root.
>>
>> * Is that truly required or is there a way to give the user access to
>> the top of the new mount point without roots' involvement?
>
> Have you tried:
>
> # cat /etc/fstab | grep VideoLib
> LABEL=VideoLib * * * * */mnt/VideoLib * * * * * ext3
> auto,rw,users,uid=X,gid=Y 0 0
>
> where X is mark's user id, and Y is users' group id?
>
> On the other hand, do you use a desktop environment? Because GNOME
> does everything you want for you, and I suppose KDE does the same.
>
> Regards.
> --
> Canek Peláez Valdés
> Posgrado en Ciencia e Ingeniería de la Computación
> Universidad Nacional Autónoma de México
>

I had not tried those but they seem to cause problems so clearly I
don't have it right yet:

c2stable ~ # cat /etc/fstab | grep VideoLib
LABEL=VideoLib /mnt/VideoLib ext3
auto,rw,users,uid=1000,gid=100 0 0
c2stable ~ #

mark@c2stable ~ $ mount /mnt/VideoLib/
mount: wrong fs type, bad option, bad superblock on /dev/sdf1,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

mark@c2stable ~ $

I tried both

uid=X,gid=Y

and

setuid=X,setgid=Y

Same results.

The man page sure reads like that should work but it didn't.

Thanks,
Mark
 
Old 04-09-2012, 09:23 PM
Mark Knecht
 
Default User can mount/umount but not write to top the new drive

On Mon, Apr 9, 2012 at 1:48 PM, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Mon, 9 Apr 2012 12:59:31 -0700, Mark Knecht wrote:
>
>> * *In the past I've gotten around this by having root mount the drive
>> and then change ownership to mark:users once it's mounted. Linux
>> remembers I've done that once and no longer requires me to do anything
>> else as root.
>
> That's right, the root of the filesystem is now owned by mark.
>
>> * *Is that truly required or is there a way to give the user access to
>> the top of the new mount point without roots' involvement?
>
> Not with a Linux filesystem[1][2], because the filesystem is owned by
> root, so only root can change that.
>
> [1] This isn't strictly true as you can do it with ACLs, but that is far
> more complex than simply chowning the root of the filesystem if that is
> all you need.
>
> [2] With Windows filesystem, there are mount options to set the default
> ownership, but that is a workaround for the differences between Linux and
> Windows metadata.
>
>
> --
> Neil Bothwick
>
> TROI : What am I sensing?? I'm sensing INCOMPETENCE, you pretentious
> bald pseudo-French dickweed!

Thanks Neil. I guess that unless we figure out Canek's uid/gid options
I'll stick with chown, etc.

Cheers,
Mark
 
Old 04-09-2012, 09:39 PM
Neil Bothwick
 
Default User can mount/umount but not write to top the new drive

On Mon, 9 Apr 2012 14:23:13 -0700, Mark Knecht wrote:

> > [2] With Windows filesystem, there are mount options to set the
> > default ownership, but that is a workaround for the differences
> > between Linux and Windows metadata.

> Thanks Neil. I guess that unless we figure out Canek's uid/gid options
> I'll stick with chown, etc.

The uid and gid options don't apply to ext? filesystems. Have another
look at the man page and you'll see they are only listed for some
non-Linux filesystems, in order to make them compatible with Linux
ownerships and permissions.


--
Neil Bothwick

God: What one human uses to persecute another.
 
Old 04-09-2012, 09:42 PM
Canek Peláez Valdés
 
Default User can mount/umount but not write to top the new drive

On Mon, Apr 9, 2012 at 4:39 PM, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Mon, 9 Apr 2012 14:23:13 -0700, Mark Knecht wrote:
>
>> > [2] With Windows filesystem, there are mount options to set the
>> > default ownership, but that is a workaround for the differences
>> > between Linux and Windows metadata.
>
>> Thanks Neil. I guess that unless we figure out Canek's uid/gid options
>> I'll stick with chown, etc.
>
> The uid and gid options don't apply to ext? filesystems. Have another
> look at the man page and you'll see they are only listed for some
> non-Linux filesystems, in order to make them compatible with Linux
> ownerships and permissions.

Oh crap, you are totally right. Sorry for the noise.

Regards.
--
Canek Peláez Valdés
Posgrado en Ciencia e Ingeniería de la Computación
Universidad Nacional Autónoma de México
 
Old 04-09-2012, 09:58 PM
Mark Knecht
 
Default User can mount/umount but not write to top the new drive

On Mon, Apr 9, 2012 at 2:39 PM, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Mon, 9 Apr 2012 14:23:13 -0700, Mark Knecht wrote:
>
>> > [2] With Windows filesystem, there are mount options to set the
>> > default ownership, but that is a workaround for the differences
>> > between Linux and Windows metadata.
>
>> Thanks Neil. I guess that unless we figure out Canek's uid/gid options
>> I'll stick with chown, etc.
>
> The uid and gid options don't apply to ext? filesystems. Have another
> look at the man page and you'll see they are only listed for some
> non-Linux filesystems, in order to make them compatible with Linux
> ownerships and permissions.
>
>
> --
> Neil Bothwick
>
> God: What one human uses to persecute another.

Apparently Canek & I do need to read more carefully. I just zoomed in
on the gid stuff from searching. I should have read the whole area.
Thanks

OK, so mounting the drive and chown-ing as root is indeed the right way to go.

Thanks,
Mark
 
Old 04-09-2012, 10:45 PM
Michael Mol
 
Default User can mount/umount but not write to top the new drive

On Mon, Apr 9, 2012 at 5:39 PM, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Mon, 9 Apr 2012 14:23:13 -0700, Mark Knecht wrote:
>
>> > [2] With Windows filesystem, there are mount options to set the
>> > default ownership, but that is a workaround for the differences
>> > between Linux and Windows metadata.
>
>> Thanks Neil. I guess that unless we figure out Canek's uid/gid options
>> I'll stick with chown, etc.
>
> The uid and gid options don't apply to ext? filesystems. Have another
> look at the man page and you'll see they are only listed for some
> non-Linux filesystems, in order to make them compatible with Linux
> ownerships and permissions.

Wouldn't it at least apply to the / mount point? (Which is the only
one at issue here, anyway...)

--
:wq
 
Old 04-10-2012, 11:18 AM
Stroller
 
Default User can mount/umount but not write to top the new drive

On 9 April 2012, at 20:59, Mark Knecht wrote:
> …
> In the past I've gotten around this by having root mount the drive
> and then change ownership to mark:users once it's mounted. Linux
> remembers I've done that once and no longer requires me to do anything
> else as root.
>
> Is that truly required or is there a way to give the user access to
> the top of the new mount point without roots' involvement?


I recall having exactly this problem years ago, and having had it explained to me here on this list.

I'm sure that if you *once* chmod / chown as root, then the permissions will be remembered correctly forever after. If you unmount and remount the drive, reboot the computer or whatever, the user will be able to write to the drive.

Do double & triple check this because, although I'm certainly fallible, I feel certain of this.

If I'm mistaken I guess you could do something involving udev mounting rules.

Note that if you use the same USB drive on different computers (or dual-boot different distros) then you have to be aware of user name vs. user ID number.

Stroller.
 

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