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Old 09-12-2012, 02:39 PM   #1
Obscurious
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Using the Recursive Switche in Commands


I recently ran into a permission problem wherein a user, belonging to the group owning the files, was not able to write. Since the write operation the user wanted to perform was a complicated Git command it was not a matter of checking one file's permissions. I simply issued


Code:
sudo chown -R git:git /home/git/projectX
sudo chmod -R g+w /home/git/projectX
The permission problem still persisted. Digging around I found that a directory

Code:
/home/git/projectX/.git/objects
was not group writable even after issuing the above commands.

Is my understanding of the -R switch wrong? The -R works in other cases on hidden directory and files. Can anyone offer some insight, please and thanks.
 
Old 09-12-2012, 03:02 PM   #2
business_kid
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sudo loses the permissions war with root on occasion. Su & password do also.

su - is better.
 
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Old 09-12-2012, 03:15 PM   #3
kakaka
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If I create a simple directory tree, and in that tree, include a directory starting with dot, chmod -R g+w changes the group write permission just fine, on the system I'm using.

Are you saying that if you look at the permissions on /home/git/projectX/.git/objects the group write bit is not set?

Or are you instead saying that when some complicated Git command is run, there are error messages?

More complete details on the situation would be helpful.

Without them, we can only guess, or try to provide rather general ideas.

Sometimes there can be issues with sudo instead of su.

Some implementations of chmod process symbolic links differently, depending on whether the link was specified on the command line or encountered recursively.
Also, sometimes there can effectively be an interaction between mode bits.

Some implementations of chmod accept a -v option which causes the command to provide a verbose description for every change it makes, or does not make.
If your chmod has that option, you could try that to see if it tells you it will not change the group write bit in some situation.

Some commands run setuid/setgid and so if the issue is error messages from some Git command, or some other command which might be involved in the more complicated situation which you mentioned in passing, then the way in which permissions are being used might be more complicated that you originally expected.

HTH.
 
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Old 09-12-2012, 03:53 PM   #4
Obscurious
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I was running as root, i.e. sudo -s.
After running chmod -R g+w /home/git/projectX the directory /home/git/projectX/.git/objects still did not have the group write bit set.
Git is abstracted from this scenario, it only informed me of permission problems.
Here is the command line output from my problem:

Code:
$ sudo -s
# cd /home/git/projectX
# ls -la
-rw-rw-r--  1 git git  996 2012-07-06 10:36 COPYRIGHT.txt
-rw-rw-r--  1 git git  720 2012-07-06 10:36 cron.php
drwxrwsr-x  8 git git 4.0K 2012-08-27 16:08 .git/

# chmod -R g+w *
# ls -la .git
drwxr--r-x 190 git git 4.0K 2012-09-07 10:43 objects/
-rw-r--r--   1 git git   41 2012-08-27 16:08 ORIG_HEAD
-rw-rw-r--   1 git git   94 2012-07-06 10:36 packed-refs

#ls -la .git/objects
drwxr--r-x 2 root    git 4.0K 2012-09-04 12:21 00/
drwxr--r-x 2 root    git 4.0K 2012-09-04 12:35 01/
drwxr--r-x 2 root    git 4.0K 2012-09-04 12:21 02/
So you can see objects and the contents of objects did not get updated.

Running a clean test, using Kakaka's suggestion of the -v option we have:

Code:
$ sudo -s
# cd /home/obscurious
# mkdir -p tmp/.hidden
# touch tmp/.hidden/testfile
# ls -la tmp/.hidden/testfile
-rw-rw-r-- 1 root root 0 2012-09-12 13:27 testfile
# chmod -Rv g+x tmp
mode of `tmp' changed to 0775 (rwxrwxr-x)
mode of `tmp/.hid' retained as 0775 (rwxrwxr-x)
mode of `tmp/.hid/testfile' changed to 0674 (rw-rwxr--)
# ls -la tmp/.hid
-rw-rw-r-- 1 root    root       0 2012-09-12 13:27 testfile
Which worked as expected and did not reproduce the problem described above. I hope this is more clear. This is an up-to-date ubuntu server 12.04, running bash.
 
Old 09-12-2012, 04:06 PM   #5
suicidaleggroll
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Quote:
Originally Posted by Obscurious View Post
Code:
mode of `tmp/.hid/testfile' changed to 0674 (rw-rwxr--)
# ls -la tmp/.hid
-rw-rw-r-- 1 root    root       0 2012-09-12 13:27 testfile
That was expected? Or was that a typo?
 
Old 09-12-2012, 05:13 PM   #6
Obscurious
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Typo thanks for catching that.
 
Old 09-12-2012, 05:37 PM   #7
chrism01
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1. Try the -v option on the real thing
2. Its possible someone has used http://linux.die.net/man/1/chattr on that file; try http://linux.die.net/man/1/lsattr to check
 
Old 09-13-2012, 02:46 AM   #8
kakaka
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Obscurious,

I had mentioned that sometimes mode bits effectively interact. Notice the s in the group section of the mode bits from this line of output you posted:

Code:
drwxrwsr-x  8 git git 4.0K 2012-08-27 16:08 .git/
If Git set that bit, then you may need to review Git's security model, because you might be effectively bypassing it by making the changes you are.

Depending on exactly how chmod is implemented in the kernel you are using, you may be able to remove the s by running:

Code:
chmod g-s .git
then if run purely as root ( that is, IF sudo -s in your environment is indeed equivalent to su - ) , the recursive chmod should likely behave as you expected.

But if Git set that bit and the original owner and group owner of the directories in the directory tree, ( possible bugs in Git not withstanding ) the bit probably shouldn't be changed, and the changes you are trying to make probably shouldn't be made.

Another possible command to investigate if there are still problems:

Code:
getfacl .git

Last edited by kakaka; 09-13-2012 at 02:57 AM.
 
  


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