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Can Dimdows do this...

 
 
shannon
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      06-11-2005
On Sat, 11 Jun 2005 12:41:20 +1200, Bling-Bling wrote:

> On Sat, 11 Jun 2005 12:13:20 +1200, shannon wrote:
>
>> They are mounted and owned by root usually.

>
> I just mounted a DVD. It went under /media/CDROM.
>
> It was not owned by the root user - or by the user a/c which mounted it.
>
>
> Bling Bling


Then it wasn't user mounted

 
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Matthew Poole
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      06-11-2005
On Sat, 11 Jun 2005 11:28:55 +1200, someone purporting to be Lawrence
DčOliveiro didst scrawl:

> In article <d8bsct$moi$(E-Mail Removed)>, "Tim" <(E-Mail Removed)>
> wrote:
>
>>It would be extremely foolish to leap in and configure a large number of
>>drives in a willy nilly manner...

>
> So does Dimdows have trouble with too many mounted filesystems?


For someone who seems to know little of nothing about the subject at hand,
you calling Windows "Dimdows" is just too precious.
There are physical and practical limitations to how many partitions you
will have in a single computer. Most systems cannot handle more than six
or eight individual hard drives, and if you're using that many you've
likely got them in some kind of array or arrays. Then there's the further
limitation of just how many partitions you're likely to need under that.

I believe that most Unix systems won't allow more than 256 mountpoints,
but by the time you hit that limit your system's complexity is well beyond
what any sane admin would put themselves through.

--
Matthew Poole
"Don't use force. Get a bigger hammer."

 
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Bling-Bling
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      06-11-2005
On Sat, 11 Jun 2005 12:50:00 +1200, shannon wrote:

>>> They are mounted and owned by root usually.

>>
>> I just mounted a DVD. It went under /media/CDROM.
>> It was not owned by the root user - or by the user a/c which mounted it.

>
> Then it wasn't user mounted


I dunno about that.

*I* clicked on the relevant icon and selected the "mount" option. As a
direct result of that the DVD was mounted. And I was not using the root
user's a/c.

All the files within the mounted DVD looks like they have a large random
number as the owner.

I could have opened up a terminal window and mounted it from the command
line with similar, albeit slower, results.


Bling Bling

--
IBM: "Linux is not just another operating system. It represents a
collaboration of the best programmers in the industry coming together to
create an operating system that works on any hardware platform."

 
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Matthew Poole
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      06-11-2005
On Sat, 11 Jun 2005 13:04:21 +1200, someone purporting to be Bling-Bling
didst scrawl:

> On Sat, 11 Jun 2005 12:50:00 +1200, shannon wrote:
>
>>>> They are mounted and owned by root usually.
>>>
>>> I just mounted a DVD. It went under /media/CDROM.
>>> It was not owned by the root user - or by the user a/c which mounted it.

>>
>> Then it wasn't user mounted

>
> I dunno about that.
>
> *I* clicked on the relevant icon and selected the "mount" option. As a
> direct result of that the DVD was mounted. And I was not using the root
> user's a/c.
>

So mount is probably SUID. That's the usual way to achieve that kind of
result. Or a special mount utility that only does DVD and CDROM drives
has been written and installed SUID. Devices are not usually accessible
to unprivileged users.

> All the files within the mounted DVD looks like they have a large random
> number as the owner.
>

The same number? Or different numbers?

> I could have opened up a terminal window and mounted it from the command
> line with similar, albeit slower, results.
>

If that's the case, it's probably mount itself which is SUID.
--
Matthew Poole
"Don't use force. Get a bigger hammer."

 
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Bling-Bling
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      06-11-2005
On Sat, 11 Jun 2005 13:14:29 +1200, Matthew Poole wrote:

>>> Then it wasn't user mounted

>>
>> I dunno about that.
>>
>> *I* clicked on the relevant icon and selected the "mount" option. As a
>> direct result of that the DVD was mounted. And I was not using the root
>> user's a/c.
>>

> So mount is probably SUID. That's the usual way to achieve that kind of
> result. Or a special mount utility that only does DVD and CDROM drives
> has been written and installed SUID. Devices are not usually accessible
> to unprivileged users.
>
>> All the files within the mounted DVD looks like they have a large random
>> number as the owner.
>>

> The same number? Or different numbers?


The same number for both user and group on all files. And it was the same
number after being unmounted and remounted again.

So it wasn't really random.


>
>> I could have opened up a terminal window and mounted it from the command
>> line with similar, albeit slower, results.
>>

> If that's the case, it's probably mount itself which is SUID.


I'd be interested to know what you mean by SUID. In what context would you
set the User ID to be different from the user who actually initiated
something?


Bling Bling

--
IBM: "Linux is not just another operating system. It represents a
collaboration of the best programmers in the industry coming together to
create an operating system that works on any hardware platform."

 
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Chris Hope
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      06-11-2005
Bling-Bling wrote:

[snip]

> In what context would
> you set the User ID to be different from the user who actually
> initiated something?


passwd is a good example of when you need to run the command as a
different user. Because it modifies important system files that are not
editiable as a normal user (such as /etc/passwd, /etc/shadow or
whatever depending on your system and how it is configured), it needs
to run with different permissions so that ordinary users are able to
change their own password.

--
Chris Hope | www.electrictoolbox.com | www.linuxcdmall.co.nz
 
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Matthew Poole
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      06-11-2005
On Sat, 11 Jun 2005 13:23:18 +1200, someone purporting to be Bling-Bling
didst scrawl:

> On Sat, 11 Jun 2005 13:14:29 +1200, Matthew Poole wrote:
>

*SNIP*
>> If that's the case, it's probably mount itself which is SUID.

>
> I'd be interested to know what you mean by SUID. In what context would you
> set the User ID to be different from the user who actually initiated
> something?
>

SUID, or Set UID isn't dynamic. It means that the executing permissions
are those of the binary's owner, not the executing user. Usually SUID is
used to make a root-owned binary execute with root permissions. It's
dangerous, because it can easily be abused or exploited, but it's also by
far the easiest way of letting users mount and unmount things like CDs and
DVDs because their devices cannot, by default, be modified by normal
users. If you see a file that has permissions like rwsr--r--, that's a
file that has had the SUID bit set. The same can be done with the group
execute permission, but I'm not sure what that actually allows.

--
Matthew Poole
"Don't use force. Get a bigger hammer."

 
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Bling-Bling
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      06-11-2005
On Sat, 11 Jun 2005 14:11:15 +1200, Matthew Poole wrote:

> On Sat, 11 Jun 2005 13:23:18 +1200, someone purporting to be Bling-Bling
> didst scrawl:
>
>> On Sat, 11 Jun 2005 13:14:29 +1200, Matthew Poole wrote:
>>

> *SNIP*
>>> If that's the case, it's probably mount itself which is SUID.

>>
>> I'd be interested to know what you mean by SUID. In what context would
>> you set the User ID to be different from the user who actually initiated
>> something?
>>

> SUID, or Set UID isn't dynamic. It means that the executing permissions
> are those of the binary's owner, not the executing user. Usually SUID is
> used to make a root-owned binary execute with root permissions. It's
> dangerous, because it can easily be abused or exploited, but it's also by
> far the easiest way of letting users mount and unmount things like CDs and
> DVDs because their devices cannot, by default, be modified by normal
> users. If you see a file that has permissions like rwsr--r--, that's a
> file that has had the SUID bit set. The same can be done with the group
> execute permission, but I'm not sure what that actually allows.


cool - thanks for the info - appreciated.


Bling Bling

--
IBM: "Linux is not just another operating system. It represents a
collaboration of the best programmers in the industry coming together to
create an operating system that works on any hardware platform."

 
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Lawrence DčOliveiro
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      06-11-2005
In article <(E-Mail Removed)>,
Matthew Poole <(E-Mail Removed)> wrote:

>I believe that most Unix systems won't allow more than 256 mountpoints...


Which is nevertheless an order of magnitude beyond that manageable with
Dimdows drive letters.
 
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Lawrence DčOliveiro
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      06-11-2005
In article <(E-Mail Removed)>,
shannon <(E-Mail Removed)> wrote:

>Different distributions mount insertable media drives in different places.
>They are mounted by root though, not user.


It is possible to specify that particular entries in /etc/fstab are
mountable by non-root users.
 
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