I would like to start a process as root upon each user login. The motivation beside this is, that the process will work on encrypted home folder of particular user folder.

How can I achieve this?

  • Then shouldn't this be the user's own process? – SailorCire Jan 19 '15 at 16:14

If your system uses PAM (most do), you can use the pam_exec module in the session stack. Note that the user won't be logged in until the command finishes; if you want to run something in the background, fork it. Several environment variables provide information about the session. For example:

session optional pam_exec.so seteuid /usr/local/sbin/my-login-process

where /usr/local/sbin/my-login-process contains something like

  exec 2>&1 >>"/var/log/my-root-service/$PAM_USER.log"
  echo "$PAM_USER logged in on $PAM_TTY on $PAM_RHOST at $(date)"
} &

In the /etc/sudoers file (shortcut visudo) add these lines:

Cmnd_Alias   CMDNAME = /path/to/binaryOrscriptToBeRunAsRoot
%groupnamehere ALL=NOPASSWD: CMDNAME

Instead of using a username only, creating a CMDNAME group and all users in that group have that permission:

groupadd groupnamehere
usermod -G groupnamehere usertoaddtogrouphere

To test this, become the user, and execute the command:

  1. Become the user => su - usernamehere
  2. Check groups user is in => groups
  3. Run command => sudo CMDNAME restart
  4. In case it isn't a global command run => sudo /path/to/binaryOrScript arg

An example of this is:


Cmnd_Alias   TESTME = /usr/local/bin/testme.sh


#netstat can only be run by root on my servers.
#File permissions are 'chmod 700'
netstat -tln |grep :80


# You need to change 'testme' in the boundry to match the groupname created
# This checks to see if the user who just logged is part of that cmdgroup, 
# if so, it runs whatever is inside.
username=`id -un`
if groups $username | grep &>/dev/null '\btestme\b'; then
        sudo /usr/local/bin/testme.sh

Login to a user of that group and see:

[nonrootuser ~]#
tcp   0  0 :::80          :::*           LISTEN

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