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#1 2018-08-23 11:38:18

jimjamz
Member
From: Nagasaki, Japan
Registered: 2016-04-04
Posts: 189

[SOLVED] Not permitted to view files on disk even with same group GID

I have an ext4 external disk that is normally connected to a file server.
For all the files on the disk, the owner is `root` and the group is `users`.

A sample directory on the disk looks like this:

root@fileserver:/media/ARCHIVE1# ls -la logs/
drwxrwxr--  2 root    users  4096 May 18 02:17 .
drwxrwxr-- 17 jimjamz users  4096 Aug  1 05:19 ..
-rwxrwxr--  1 root    users 93764 Feb 26  2016 AVSCAN-20160225-214734-AB9989CA.LOG
-rwxrwxr--  1 root    users 80226 Mar 25  2016 AVSCAN-20160324-113755-5CAA2791.LOG
-rwxrwxr--  1 root    users  4359 Jul 12  2016 diff_20160611.log
-rwxrwxr--  1 root    users   890 May 28  2017 diff_20161010.log
-rwxrwxr--  1 root    users 45911 Oct 14  2016 diff_20161013.log
-rwxrwxr--  1 root    users 46636 Oct 16  2016 diff_20161015.log
-rwxrwxr--  1 root    users 22300 May 28  2017 diff_20161025.log
-rwxrwxr--  1 root    users 37032 Nov  1  2016 diff_20161101.log
-rwxrwxr--  1 root    users 45926 Nov 12  2016 diff_20161112.log
-rwxrwxr--  1 root    users 43374 Dec 31  2016 diff_20161231.log
-rwxrwxr--  1 root    users 54553 May 18 02:17 diff_dir.log
-rwxrwxr--  1 root    users  1551 May 28  2017 fsum_openssl_conversion.log

On my bunsenlabs laptop, I have created and added myself to a group also called `users`:

sudo useradd -g users jimjamz

However, when I connect the disk to my bunsenlabs laptop, and try to view the same directory, I see:

jimjamz@bunsen-mac:/media/jimjamz/ARCHIVE1$ ls -la logs/
ls: cannot access 'logs/diff_20161013.log': Permission denied
ls: cannot access 'logs/AVSCAN-20160225-214734-AB9989CA.LOG': Permission denied
ls: cannot access 'logs/diff_20161025.log': Permission denied
ls: cannot access 'logs/diff_dir.log': Permission denied
ls: cannot access 'logs/.': Permission denied
ls: cannot access 'logs/diff_20161015.log': Permission denied
ls: cannot access 'logs/diff_20161010.log': Permission denied
ls: cannot access 'logs/fsum_openssl_conversion.log': Permission denied
ls: cannot access 'logs/diff_20160611.log': Permission denied
ls: cannot access 'logs/diff_20161231.log': Permission denied
ls: cannot access 'logs/diff_20161101.log': Permission denied
ls: cannot access 'logs/diff_20161112.log': Permission denied
ls: cannot access 'logs/AVSCAN-20160324-113755-5CAA2791.LOG': Permission denied
ls: cannot access 'logs/..': Permission denied
total 0
d????????? ? ? ? ?            ? .
d????????? ? ? ? ?            ? ..
-????????? ? ? ? ?            ? AVSCAN-20160225-214734-AB9989CA.LOG
-????????? ? ? ? ?            ? AVSCAN-20160324-113755-5CAA2791.LOG
-????????? ? ? ? ?            ? diff_20160611.log
-????????? ? ? ? ?            ? diff_20161010.log
-????????? ? ? ? ?            ? diff_20161013.log
-????????? ? ? ? ?            ? diff_20161015.log
-????????? ? ? ? ?            ? diff_20161025.log
-????????? ? ? ? ?            ? diff_20161101.log
-????????? ? ? ? ?            ? diff_20161112.log
-????????? ? ? ? ?            ? diff_20161231.log
-????????? ? ? ? ?            ? diff_dir.log
-????????? ? ? ? ?            ? fsum_openssl_conversion.log

When I view the groups I am part of:

id jimjamz

the result is:

uid=1000(jimjamz) gid=1000(jimjamz) groups=1000(jimjamz),24(cdrom),25(floppy),27(sudo),29(audio),30(dip),44(video),46(plugdev),100(users),108(netdev)

To confirm that the `users` group on the disk has the same GID as the `users` group on my laptop, I changed the group's GID then rebooted:

sudo groupmod -g 1004 users

and after reboot, I checked the directory again to see the gid value for the `users` group on the disk is also '100'.  It shows '100' instead of 'users' because it is a group not recognised.

drwxrwxr--   2 root        100  4096 May 18 02:17 logs

So I changed the GID back to 100.  One can see that the gid is recognised once again as 'users'.

drwxrwxr--   2 root        users  4096 May 18 02:17 logs

So I am a member of the same `users` group with the same GID as on the disk, and have sufficient permissions to read and write to the directory, but am still not able to access it.

The only ways I know to make the directory viewable to me on my laptop, is to either loosen the permissions on the directory:

sudo chmod 775 -R /media/jimjamz/ARCHIVE1/logs/

But I shouldn't need to do that as the current permissions (774) should be sufficient.  However, increasing to 775 does make the directory accessible:

jimjamz@bunsen-mac:/media/jimjamz/ARCHIVE1$ ls -la logs/
total 504
drwxrwxr-x  2 root    users  4096 May 18 02:17 .
drwxrwxr-- 17 jimjamz users  4096 Aug  1 05:19 ..
-rwxrwxr-x  1 root    users 93764 Feb 26  2016 AVSCAN-20160225-214734-AB9989CA.LOG
-rwxrwxr-x  1 root    users 80226 Mar 25  2016 AVSCAN-20160324-113755-5CAA2791.LOG
-rwxrwxr-x  1 root    users  4359 Jul 12  2016 diff_20160611.log
-rwxrwxr-x  1 root    users   890 May 28  2017 diff_20161010.log
-rwxrwxr-x  1 root    users 45911 Oct 14  2016 diff_20161013.log
-rwxrwxr-x  1 root    users 46636 Oct 16  2016 diff_20161015.log
-rwxrwxr-x  1 root    users 22300 May 28  2017 diff_20161025.log
-rwxrwxr-x  1 root    users 37032 Nov  1  2016 diff_20161101.log
-rwxrwxr-x  1 root    users 45926 Nov 12  2016 diff_20161112.log
-rwxrwxr-x  1 root    users 43374 Dec 31  2016 diff_20161231.log
-rwxrwxr-x  1 root    users 54553 May 18 02:17 diff_dir.log
-rwxrwxr-x  1 root    users  1551 May 28  2017 fsum_openssl_conversion.log

Reducing back to 774 makes the directory inaccessible once again.  Why?  I don't understand why the extra execute permissions change the accessibility.

The other way is to change the ownership to me:

sudo chown jimjamz -R /media/jimjamz/ARCHIVE1/logs/

I won't and shouldn't have to do that either, just to be able to view the files.

Last edited by jimjamz (2018-08-24 11:46:53)

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#2 2018-08-23 17:20:00

nobody
The Great
Registered: 2015-08-10
Posts: 3,655

Re: [SOLVED] Not permitted to view files on disk even with same group GID

In order to access directories, the mode MUST have the executable bit set, that is 775 is the correct mode for the directory while 774 is just wrong (otherwise, the mode would be 664 at most).

For accessing files, the octal mode is '6', that is 664 for rwrwr.

When changing group affiliation, you need to log in/log out in general for the change to become active for your user (or log in using another session).

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#3 2018-08-24 00:23:23

johnraff
nullglob
From: Nagoya, Japan
Registered: 2015-09-09
Posts: 12,674
Website

Re: [SOLVED] Not permitted to view files on disk even with same group GID

twoion wrote:

In order to access directories, the mode MUST have the executable bit set

...so you might check the permissions on the directory /media/ARCHIVE1/logs

Last edited by johnraff (2018-08-24 00:24:03)

...elevator in the Brain Hotel, broken down but just as well...
( a boring Japan blog (currently paused), now on Bluesky, there's also some GitStuff )

Introduction to the Bunsenlabs Boron Desktop

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#4 2018-08-24 11:34:39

jimjamz
Member
From: Nagasaki, Japan
Registered: 2016-04-04
Posts: 189

Re: [SOLVED] Not permitted to view files on disk even with same group GID

But the executable permission is set for both owner and group, which is what my user on the Bunsenlabs laptop is a member of:

id jimjamz

response:

uid=1000(jimjamz) gid=1000(jimjamz) groups=1000(jimjamz),24(cdrom),25(floppy),27(sudo),29(audio),30(dip),44(video),46(plugdev),100(users),108(netdev)

The permissions, `drwxrwxr--` would indicate that the directory/file is executable for both owner and group.

Last edited by jimjamz (2018-08-24 11:35:21)

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#5 2018-08-24 11:45:31

jimjamz
Member
From: Nagasaki, Japan
Registered: 2016-04-04
Posts: 189

Re: [SOLVED] Not permitted to view files on disk even with same group GID

OK, this is strange.  I haven't changed anything, except shutting down and powering the laptop back on with the disk connected.  Now, the files are accessible.

I logged out/in and rebooted many times whilst testing this to see the changes reflected, but it always said not permitted.

So here is how the directory currently looks:

jimjamz@bunsen-mac:~$ ls -la /media/jimjamz/ARCHIVE1/logs/
total 504
drwxrwxr--  2 root    users  4096 May 18 02:17 .
drwxrwxr-- 17 jimjamz users  4096 Aug  1 05:19 ..
-rwxrwxr--  1 root    users 93764 Feb 26  2016 AVSCAN-20160225-214734-AB9989CA.LOG
-rwxrwxr--  1 root    users 80226 Mar 25  2016 AVSCAN-20160324-113755-5CAA2791.LOG
-rwxrwxr--  1 root    users  4359 Jul 12  2016 diff_20160611.log
-rwxrwxr--  1 root    users   890 May 28  2017 diff_20161010.log
-rwxrwxr--  1 root    users 45911 Oct 14  2016 diff_20161013.log
-rwxrwxr--  1 root    users 46636 Oct 16  2016 diff_20161015.log
-rwxrwxr--  1 root    users 22300 May 28  2017 diff_20161025.log
-rwxrwxr--  1 root    users 37032 Nov  1  2016 diff_20161101.log
-rwxrwxr--  1 root    users 45926 Nov 12  2016 diff_20161112.log
-rwxrwxr--  1 root    users 43374 Dec 31  2016 diff_20161231.log
-rwxrwxr--  1 root    users 54553 May 18 02:17 diff_dir.log
-rwxrwxr--  1 root    users  1551 May 28  2017 fsum_openssl_conversion.log

As you can see, I'm logged in as myself (not root), and the permissions are still currently 774.  I have full read/write access, so it must have now registered that the users group on the disk is the same users group that I am a member of.

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#6 2018-08-25 02:08:40

johnraff
nullglob
From: Nagoya, Japan
Registered: 2015-09-09
Posts: 12,674
Website

Re: [SOLVED] Not permitted to view files on disk even with same group GID

(BTW my question was about the permissions set on the directory /media/ARCHIVE1/logs itself, not its contents. ie 'ls -l /media/ARCHIVE1' and look at the logs entry. But it's fixed now anyway.)

...elevator in the Brain Hotel, broken down but just as well...
( a boring Japan blog (currently paused), now on Bluesky, there's also some GitStuff )

Introduction to the Bunsenlabs Boron Desktop

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