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Old 08-25-2011, 10:52 PM
Blair Mason
 
Default sharing one r/w unix filesystem between different machines and users

Can you use the other permission set? Or does it need to be specifically those users only? Permission schemes on removable media are not too powerful annyway, as anyone with root on any machine can change them... my $0.02.

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Old 08-25-2011, 11:02 PM
Christoph Groth
 
Default sharing one r/w unix filesystem between different machines and users

Blair Mason <rbmj@verizon.net> writes:

> Permission schemes on removable media are not too powerful annyway, as
> anyone with root on any machine can change them... my $0.02.

Exactly -- I wonder whether there are any decent (modern features,
public specification, nice free implementation, etc.) filesystems which
allow to ignore permissions when mounted by a user.


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Old 08-26-2011, 01:06 AM
"Robert Blair Mason Jr."
 
Default sharing one r/w unix filesystem between different machines and users

On Fri, 26 Aug 2011 01:02:57 +0200
Christoph Groth <cwg@falma.de> wrote:

> Blair Mason <rbmj@verizon.net> writes:
>
> > Permission schemes on removable media are not too powerful annyway,
> > as anyone with root on any machine can change them... my $0.02.
>
> Exactly -- I wonder whether there are any decent (modern features,
> public specification, nice free implementation, etc.) filesystems
> which allow to ignore permissions when mounted by a user.
>
>

Will something like the following work? This works on any filesystem
using standard unix permissions (such as ext*, ufs, reiserfs*, btrfs,
etc.)

Suppose your filesystem is mounted on /media/usb0.

# chmod -R a+rwx /media/usb0

This does, however, seem the Wrong Way To Do It, as it will not work
for files created after issuing the command. Unfortunately, there isn't
an elegant way to do this. It seems like it should be an option
to mount (something like ignoreperms). Looking at the internet, it
appears that OSX has a mount option to do this:

http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man8/mount.8.html
(search for 'noowners')

This option does not appear to exist on Linux or BSD, however.

Hope this helps,

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Old 08-26-2011, 03:30 AM
shawn wilson
 
Default sharing one r/w unix filesystem between different machines and users

On Thu, Aug 25, 2011 at 19:02, Christoph Groth <cwg@falma.de> wrote:
> Blair Mason <rbmj@verizon.net> writes:
>
>> Permission schemes on removable media are not too powerful annyway, as
>> anyone with root on any machine can change them... my $0.02.
>
> Exactly -- I wonder whether there are any decent (modern features,
> public specification, nice free implementation, etc.) filesystems which
> allow to ignore permissions when mounted by a user.
>

so, the old school way is to use nis (or ypbind). this will still work
for you (it isn't secure but you can set it up in a few minutes. the
modern way is ldap and a ticketing system (kerberos) but seriously,
don't try - it's hard and overkill.

the end result is to have global uid / gid. then you setup nfs and
export for that ip / mask and you can mount it from your remote host.
what i'd suggest is to export /mnt and have your host automatically
mount devices under a subdirectory to /mnt and then you'll be able to
read it from your remote host. you could even have udev do a
'notify-send' to your remote machines when you insert media (but,
obviously this is overkill since you know when you've inserted media
into your own computers - just fun ).


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Old 08-26-2011, 06:41 AM
Christoph Groth
 
Default sharing one r/w unix filesystem between different machines and users

"Robert Blair Mason Jr." <rbmj@verizon.net> writes:

> Christoph Groth <cwg@falma.de> wrote:
>
>> Blair Mason <rbmj@verizon.net> writes:
>>
>> > Permission schemes on removable media are not too powerful annyway,
>> > as anyone with root on any machine can change them... my $0.02.
>>
>> Exactly -- I wonder whether there are any decent (modern features,
>> public specification, nice free implementation, etc.) filesystems
>> which allow to ignore permissions when mounted by a user.
>>
> Will something like the following work? This works on any filesystem
> using standard unix permissions (such as ext*, ufs, reiserfs*, btrfs,
> etc.)
>
> Suppose your filesystem is mounted on /media/usb0.
>
> # chmod -R a+rwx /media/usb0
>
> This does, however, seem the Wrong Way To Do It, as it will not work
> for files created after issuing the command.

That's the point. If user A creates some directory, and user B (who has
a different uid on his machine) wants to delete a file in this
directory, user B will have first to become root and override the
permissions. This is an unnecessary hassle and requires the user in
question to be fairly technical. And it won't work if the user is
unable to become root.

> Unfortunately, there isn't an elegant way to do this. It seems like it
> should be an option to mount (something like ignoreperms). Looking at
> the internet, it appears that OSX has a mount option to do this:
>
> http://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man8/mount.8.html
> (search for 'noowners')
>
> This option does not appear to exist on Linux or BSD, however.

Thanks, I've been looking for something like this (though an OSX
solution doesn't help me). I really wonder why no one has ever fixed
this issue for Linux -- probably everybody is happy simply using FAT and
NTFS on shared removable media. And their importance is fading anyway.

Thanks,
Christoph


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Old 08-26-2011, 06:54 AM
Christoph Groth
 
Default sharing one r/w unix filesystem between different machines and users

shawn wilson <ag4ve.us@gmail.com> writes:

> On Thu, Aug 25, 2011 at 19:02, Christoph Groth <cwg@falma.de> wrote:
>> Blair Mason <rbmj@verizon.net> writes:
>>
>>> Permission schemes on removable media are not too powerful annyway, as
>>> anyone with root on any machine can change them... my $0.02.
>>
>> Exactly -- I wonder whether there are any decent (modern features,
>> public specification, nice free implementation, etc.) filesystems which
>> allow to ignore permissions when mounted by a user.

Thanks, but any solution requiring to run additional servers to solve
this simple issue doesn't feel like the proper one.

I think the idea that a user should be able to control _fully_ the
devices which he attaches himself is not really supported well in Linux.
The issue is not trivial to solve, because who should own a newly
attached device if several users are logged in? (It should be the
current user of the physical terminal to which the new device has been
connected.)

Is anyone aware of an emerging solution to this?

Christoph


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Old 08-26-2011, 09:29 AM
"Lars Maes"
 
Default sharing one r/w unix filesystem between different machines and users

Hi Christoph,

Why not use an UDF filesystem, that is used on DVD discs?


"Christoph Groth" schreef in bericht news:87hb55ku8x.fsf@falma.de...


Hi,

I'd like to share the data saved on an external USB drive between
different (GNU/Linux) machines, each having different users. Each user
should be able to mount the drive and read and write any files as he or
she pleases. The users aren't necessary root themselves.

Is there a way to implement such a scheme with a non-windows filesystem
like ext3?

I understand how Unix file permissions work. However, for a removable
drive which might be connected to different systems (with completely
unrelated uids/gids), assigning fixed uids/gids to files just doesn't
make any sense.

What's the best FS for sharing data between unrelated Linux systems? Is
it really FAT or NTFS?

Thanks,
Christoph



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Old 08-28-2011, 02:01 PM
"Robert Blair Mason Jr."
 
Default sharing one r/w unix filesystem between different machines and users

On Fri, 26 Aug 2011 08:41:35 +0200
Christoph Groth <cwg@falma.de> wrote:

> "Robert Blair Mason Jr." <rbmj@verizon.net> writes:
>
> > Christoph Groth <cwg@falma.de> wrote:
> >
> > Will something like the following work? This works on any filesystem
> > using standard unix permissions (such as ext*, ufs, reiserfs*,
> > btrfs, etc.)
> >
> > Suppose your filesystem is mounted on /media/usb0.
> >
> > # chmod -R a+rwx /media/usb0
> >
> > This does, however, seem the Wrong Way To Do It, as it will not work
> > for files created after issuing the command.
>
> That's the point. If user A creates some directory, and user B (who
> has a different uid on his machine) wants to delete a file in this
> directory, user B will have first to become root and override the
> permissions. This is an unnecessary hassle and requires the user in
> question to be fairly technical. And it won't work if the user is
> unable to become root.
>
> > Unfortunately, there isn't an elegant way to do this. It seems like
> > it should be an option to mount (something like ignoreperms).
> > Looking at the internet, it appears that OSX has a mount option to
> > do this:
> >
> > http://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man8/mount.8.html
> > (search for 'noowners')
> >
> > This option does not appear to exist on Linux or BSD, however.
>
> Thanks, I've been looking for something like this (though an OSX
> solution doesn't help me). I really wonder why no one has ever fixed
> this issue for Linux -- probably everybody is happy simply using FAT
> and NTFS on shared removable media. And their importance is fading
> anyway.
>

I understand OSX doesn't help anyone here... perhaps someone could
request an implementation of this command in the mount source code?
It seems simple - just check if the filesystem has noowners set and if
so, instead of fetching permissions from disk, return -rwxrwxrwx. But
these things are never as simple as they seem...

--
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Old 08-28-2011, 05:31 PM
"Robert Blair Mason Jr."
 
Default sharing one r/w unix filesystem between different machines and users

On Sun, 28 Aug 2011 10:01:05 -0400
"Robert Blair Mason Jr." <rbmj@verizon.net> wrote:
>
> I understand OSX doesn't help anyone here... perhaps someone could
> request an implementation of this command in the mount source code?
> It seems simple - just check if the filesystem has noowners set and if
> so, instead of fetching permissions from disk, return -rwxrwxrwx. But
> these things are never as simple as they seem...
>

Actually, a quick skim over the mount(8) source code shows that all of
the changes would actually have to be done in the mount(2) source code
- which I believe is in the kernel

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Old 08-28-2011, 11:18 PM
shawn wilson
 
Default sharing one r/w unix filesystem between different machines and users

I don't understand what is hard about this. I mean if you don't care about security, just make sure the mount has a umask of 770 (or whatever) and make an export, reload exports, and mount it from wherever you want.



What am I missing?


Also, if you want to call osx Unix, call it broken unix. Most people say its 'unix like' though. What I mean is that Apple changed basic unix commands around which osx not act right. And then it is possibly closer in comparison to windows than it is to Linux.


On Aug 28, 2011 3:33 PM, "Robert Blair Mason Jr." <rbmj@verizon.net> wrote:> On Sun, 28 Aug 2011 10:01:05 -0400

> "Robert Blair Mason Jr." <rbmj@verizon.net> wrote:
>>
>> I understand OSX doesn't help anyone here... perhaps someone could
>> request an implementation of this command in the mount source code?

>> It seems simple - just check if the filesystem has noowners set and if
>> so, instead of fetching permissions from disk, return -rwxrwxrwx. But
>> these things are never as simple as they seem...

>>
>
> Actually, a quick skim over the mount(8) source code shows that all of
> the changes would actually have to be done in the mount(2) source code
> - which I believe is in the kernel

>
> --
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>
>
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