Need to restrict the normal users to run only limited set of commands assigned to him/her and all other commands for which normal user have permission to execute by-default, shall not be executed.
E.g: user XYZ can run only
The normal user has been given permission to execute some commands which are available in
/usr/local/bin/, So to remove those permissions and to restrict the user to run only particular set of commands, following steps shall be useful.
1. Create the restricted shell.
# cp /bin/bash /bin/rbash
2. Modify the target user for the shell as restricted shell
While creating user:
# useradd -s /bin/rbash localuser
For existing user:
# usermod -s /bin/rbash localuser
Then the user
chrooted and can’t access the links outside his home directory
3. Create a directory under
/home/localuser/, e.g. programs
# mkdir /home/localuser/programs
4. Now if you check, the user
localuser can access all commands which he/she has allowed to execute. These commands are taken from the environmental
PATH variable which is set in
/home/localuser/.bash_profile. Modify it as follows.
# cat /home/localuser/.bash_profile # .bash_profile # Get the aliases and functions if [ -f ~/.bashrc ]; then . ~/.bashrc fi # User specific environment and startup programs PATH=$HOME/programs export PATH
PATH variable is set to
~/programs directory, as
/usr/local/bin is binded to
/bin is binded to
/home/username/bin so replacing that.
5. Now after logging with the username
localuser, user cant run a simple command too. The output will be like this,
[[email protected] ~]$ ls -rbash: ls: command not found [[email protected] ~]$ less file1 -rbash: less: command not found [[email protected] ~]$ clear -rbash: clear: command not found [[email protected] ~]$ date -rbash: date: command not found [[email protected] ~]$ ping redhat.com -rbash: ping: command not found
6. Now create the softlinks of commands which are required for user
localuser to execute in the directory
# ln -s /bin/date /home/localuser/programs/ # ln -s /bin/ls /home/localuser/programs/ # ll /home/localuser/programs/ total 8 lrwxrwxrwx 1 root root 9 Oct 17 15:53 date -> /bin/date lrwxrwxrwx 1 root root 7 Oct 17 15:43 ls -> /bin/ls
Here examples of date and ls commands has been taken
7. Again login with user
localuser and try to execute the commands.
[[email protected] ~]$ date Mon Oct 17 15:55:45 IST 2011 [[email protected] ~]$ ls file1 file10 file2 file3 file4 file5 file6 file7 file8 file9 programs [[email protected] ~]$ clear -rbash: clear: command not found
8. One more step can be added to restrict the user for making any modifications in their
.bash_profile , as users can change it.
Run the following command to make the user
.bash_profile file as immutable so that root/localuser can’t modify it until root removes immutable permission from it.
# chattr +i /home/localuser/.bash_profile
To remove immutable tag,
# chattr -i /home/localuser/.bash_profile
Make file .bash_profile as
immutable so that user
localuser can’t change the environmental paths.