Tuesday, February 2, 2010

HOWTO allow multiple users write access to a directory without changing umask

I have often run into the problem of giving multiple users write access to a code repo. The main problem is what permissions are set on files which are added in new commits. The default umask is 022, so you get directories as 755 and files as 644, which obviously doesn't work.

The solution I have used in the past is to change the umask in /etc/profile and /etc/login.defs to 002. You have to do both, otherwise files added via ssh and other means don't get the right mask. The disadvantage is that now all files get created as 775,664, when you only really need it for one directory. There is a better way, enter filesystem acls.

First, change your /etc/fstab to include the 'acl' option for the mount point where your repo resides:

/dev/sda1 / ext3 defaults,acl 0 0

Do some of the regular prep to make sure you files are owned right, and dirs have the sticky bit set.

chown -R user:group /code
chown -R g+w /code
find /code -type d -exec chmod g+s {} \;

Use setfacl to set the default acls for new files and directories:

setfacl -R -m d:u::rwx,d:g::rwx,d:o:r-x /code

And check the result with 'getfacl'. Also when you use 'ls', you should see a '+' at the end of the usual permissions string that indicates there are more acls:


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