Linux: how to create a super user

Attempting to expand on @Zoredache's answer, as I give this a go myself:

• Create a new group (www-pub) and add the users to that group

  groupadd www-pub

  usermod -a -G www-pub usera ## must use -a to append to existing groups

  usermod -a -G www-pub userb

  groups usera ## display groups for user

• Change the ownership of everything under /var/www to root:www-pub

  chown -R root:www-pub /var/www ## -R for recursive

• Change the permissions of all the folders to 2775

  chmod 2775 /var/www ## 2=set group id, 7=rwx for owner (root), 7=rwx for group (www-pub), 5=rx for world (including apache www-data user)

  Set group ID (SETGID) bit (2) causes the group (www-pub) to be copied to all new files/folders created in that folder. Other options are SETUID (4) to copy the user id, and STICKY (1) which I think lets only the owner delete files.

  There's a -R recursive option, but that won't discriminate between files and folders, so you have to use find, like so:

  find /var/www -type d -exec chmod 2775 {} +

• Change all the files to 0664

  find /var/www -type f -exec chmod 0664 {} +

• Change the umask for your users to 0002

  The umask controls the default file creation permissions, 0002 means files will have 664 and directories 775. Setting this (by editing the umask line at the bottom of /etc/profile in my case) means files created by one user will be writable by other users in the www-group without needing to chmod them.

Test all this by creating a file and directory and verifying the owner, group and permissions with ls -l.

Note: You'll need to logout/in for changes to your groups to take effect!

After more research it seems like another (possibly better way) to answer this would be to setup the www folder like so.

1. sudo usermod -a -G developer user1 (add each user to developer group)
2. sudo chgrp -R developer /var/www/site.com/ so that developers can work in there
3. sudo chmod -R 2774 /var/www/site.com/ so that only developers can create/edit files (other/world can read)
4. sudo chgrp -R www-data /var/www/site.com/uploads so that www-data (apache/nginx) can create uploads.

Since git runs as whatever user is calling it, then as long as the user is in the "developer" group they should be able to create folders, edit PHP files, and manage the git repository.

Note: In step (3): '2' in 2774 means to 'set Group ID' for the directory. This causes new files and sub directories created within it to inherit the group ID of the parent directory (instead of the primary group of the user) Reference: http://en.wikipedia.org/wiki/Setuid#setuid_and_setgid_on_directories