What does chmod 775 mean? Shared folder permissions for a team

In octal, the owner's digit is 7, read, write and execute. The group digit is 7, so the group gets read, write and execute too. Others get 5, made from 4+1, so they can read and enter but not write.

The mode alone doesn't make a team folder. Pick a group with only the people who need access, then point the folder at it. Here's a setup with made-up names: the folder is /srv/project and the group is developers. chgrp developers /srv/project sets the group, chmod 775 /srv/project sets the mode, and chmod g+s /srv/project makes new files get the folder's group instead of the creator's.

Compared with 777, others lose write access. They can still read and enter, so see the chmod 777 page for why full write access is risky.

The group is the real access list. groups username shows the groups one user belongs to, so run it for each person on the team and for anyone who shouldn't have access. If someone who shouldn't write there is in the group, make a smaller group.

The folder's mode doesn't set the mode of the files inside. A new file takes its mode from the umask, and with umask 022, which many Linux systems use by default, that's 644, so the group can't write to it. Run umask 002 in each teammate's shell or profile, and new files come out as 664, which the group can write. Files that already exist need chmod g+w on them. New subfolders follow the umask too, so at 022 a new folder is 755, and the group can't add files to it.

Skip 775 for a folder that holds secrets, or where the group is large or unclear, since every member can write to the folder. A web root that nobody else should write to belongs at 755, or 750 if a group needs to read it.