Red Hat System Administration I

Log in as alice on your serverX virtual machine and open a window with a Bash prompt. Use the umask command without arguments to display Alice's default umask value.

[alice@serverX ~]$ umask
0002

Create a new directory /tmp/shared and a new file /tmp/shared/defaults to see how the default umask affects permissions.

[alice@serverX ~]$ mkdir /tmp/shared
[alice@serverX ~]$ ls -ld /tmp/shared
drwxrwxr-x. 2 alice alice 6 Jan 26 18:43 /tmp/shared
[alice@serverX ~]$ touch /tmp/shared/defaults
[alice@serverX ~]$ ls -l /tmp/shared/defaults
-rw-rw-r--. 1 alice alice 0 Jan 26 18:43 /tmp/shared/defaults

Change the group ownership of /tmp/shared to ateam and record the new ownership and permissions.

[alice@serverX ~]$ chown :ateam /tmp/shared
[alice@serverX ~]$ ls -ld /tmp/shared
drwxrwxr-x. 2 alice ateam 21 Jan 26 18:43 /tmp/shared

Create a new file in /tmp/shared and record the ownership and permissions.

[alice@serverX ~]$ touch /tmp/shared/alice3
[alice@serverX ~]$ ls -l /tmp/shared/alice3
-rw-rw-r--. 1 alice alice 0 Jan 26 18:46 /tmp/shared/alice3

Ensure the permissions of /tmp/shared cause files created in that directory to inherit the group ownership of ateam.

[alice@serverX ~]$ chmod g+s /tmp/shared
[alice@serverX ~]$ ls -ld /tmp/shared
drwxrwsr-x. 2 alice ateam 34 Jan 26 18:46 /tmp/shared
[alice@serverX ~]$ touch /tmp/shared/alice4
[alice@serverX ~]$ ls -l /tmp/shared/alice4
-rw-rw-r--. 1 alice ateam 0 Jan 26 18:48 /tmp/shared/alice4

Change the umask for alice such that new files are created with read-only access for the group and no access for other users. Create a new file and record the ownership and permissions.

[alice@serverX ~]$ umask 027
[alice@serverX ~]$ touch /tmp/shared/alice5
[alice@serverX ~]$ ls -l /tmp/shared/alice5
-rw-r-----. 1 alice ateam 0 Jan 26 18:48 /tmp/shared/alice5

Open a new Bash shell as alice and view the umask.

[alice@serverX ~]$ umask
0002

Change the default umask for alice to prohibit all access for users not in their group.

[alice@serverX ~]# echo "umask 007" >> ~/.bashrc
[alice@serverX ~]# cat ~/.bashrc
# .bashrc

# Source global definitions
if [ -f /etc/bashrc ]; then
	. /etc/bashrc
fi

# Uncomment the following line if you don't like systemctl's auto-paging feature:
# export SYSTEMD_PAGER=

# User specific aliases and functions
umask 007

Log out and back into serverX as alice and confirm that the umask changes you made are persistent.

[alice@serverX ~]$ umask
0007