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-   -   Where does the plus sign in file permissions come from? (http://www.linux-archive.org/ubuntu-desktop/342538-where-does-plus-sign-file-permissions-come.html)

Otto Kekäläinen 03-16-2010 07:01 PM

Where does the plus sign in file permissions come from?
 
Hello,

Listing of ls -la /dev/dvb/adapter0/ shows:
drwxr-xr-x 2 root root 140 2010-03-14 08:20 .
drwxr-xr-x 3 root root 60 2010-03-14 08:20 ..
crw-rw----+ 1 root video 212, 4 2010-03-14 08:20 ca0
crw-rw----+ 1 root video 212, 0 2010-03-14 08:20 demux0
crw-rw----+ 1 root video 212, 1 2010-03-14 08:20 dvr0
crw-rw----+ 1 root video 212, 3 2010-03-14 08:20 frontend0
crw-rw----+ 1 root video 212, 2 2010-03-14 08:20 net0

Where does the +-sign come from?

As far as I know, Ubuntu does not use ACL by default.

According to "info coreutils 'ls invocation'":

A file with any other combination of alternate access methods is
marked with a `+' character.

What is the alternate access method in this case? Something related to
AppArmor or PolicyKit?


I'm trying to debug an issue, which appears in pair with the plus sings
in file permissions. It would be very helpful I somebody could point to
what package makes those attributes..



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Martin Pitt 03-16-2010 07:22 PM

Where does the plus sign in file permissions come from?
 
Hello Otto,

Otto Kekäläinen [2010-03-16 22:01 +0200]:
> crw-rw----+ 1 root video 212, 4 2010-03-14 08:20 ca0
> [...]
>
> Where does the +-sign come from?
>
> As far as I know, Ubuntu does not use ACL by default.

It's indeed from ACLs, and Ubuntu has used ACLs on devices since
around hardy. First it came from hal, and in karmic the equivalent
functionality moved to udev (see /lib/udev/rules.d/70-acl.rules)

Martin
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Martin Pitt 03-17-2010 07:59 AM

Where does the plus sign in file permissions come from?
 
Hello Otto,

Otto Kekäläinen [2010-03-17 9:43 +0200]:
> Ok, thanks. The bug is maybe a regression. Are there any significant
> changes to ACL in Lucid?

Not compared to Karmic, it hardly changed at all.

> The symptom involves that sometimes the ACL is on and sometimes off.
> Is there something else that puts the ACL on/off that the udev init
> script?

No, the udev script should be the only one. The intention is that the
user who has the current foreground console gets those extra ACL
privileges, and other users get them revoked if they loose the
foreground console (i. e. for user switching, etc.). This ensures that
hardware that you plug in gets activated for the "current" user.

Under which circumstances are they off for you?

Martin

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Otto Kekäläinen 03-17-2010 07:00 PM

Where does the plus sign in file permissions come from?
 
Lainaus Martin Pitt <martin.pitt@ubuntu.com>:
>> The symptom involves that sometimes the ACL is on and sometimes off.
>> Is there something else that puts the ACL on/off that the udev init
>> script?
>
> No, the udev script should be the only one. The intention is that the
> user who has the current foreground console gets those extra ACL
> privileges, and other users get them revoked if they loose the
> foreground console (i. e. for user switching, etc.). This ensures that
> hardware that you plug in gets activated for the "current" user.

Oh, that explains a lot. If the ACL also forbids users to shutdown the
computer unless they are the only user logged in and their console is
active?

These lines in syslog are probably related?:
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Could not
determine active console
Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error
waiting for native console 4 activation: Invalid argument


> Under which circumstances are they off for you?

It occurs randomly. ACL might be off right from boot or after using
the computer for some time. 75% of the time ACL is on and works just
fine.

More details in the bug report itself:

https://bugs.launchpad.net/ubuntu/+bug/537596

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Martin Pitt 03-30-2010 06:34 AM

Where does the plus sign in file permissions come from?
 
Otto Kekäläinen [2010-03-17 22:00 +0200]:
> Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Could not
> determine active console
> Mar 17 21:40:42 shuttle console-kit-daemon[874]: WARNING: Error
> waiting for native console 4 activation: Invalid argument

For the record, this is LP #544139.

Martin
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