1. Presented by, Mr. Satish Pise
Experiment No. 5
Presented by,
Mr. Satish Pise

2. SGID, SUID and sticky bit
The set user id (SUID): When a file is executed by a user, the program runs under the permissions of the file owner.
The set group id (SGID): For a file, the program runs under the permissions of the file group. For a directory, new files created in the directory use the directory group as the default group.
The sticky bit: The file remains (sticks) in memory after the process ends.

3. The SGID bit is important for sharing files.

4. Options for permissions
■ u for the user
■ g for the group
■ o for others (everyone else)
■ a for all of the above
■ x to assign execute permissions only if the object is a directory or if it already had execute permissions.
■ s to set the UID or GID on execution
■ t to save program text
■ u to set the permissions to the owner’s permissions
■ g to set the permissions to the group’s permissions
■ o to set the permissions to the other’s permissions
Security: Minimize use of setuid and setgid programs owned by root

5. Assign SUID to a File : # chmod u+s testfile
Assign SUID to a File : # chmod u+s testfile.txt OR # chmod 4750 testfile.txt Assign SGID to a file : # chmod g+s lpr.txt # chmod 2750 lpr.txt Here in 2750, 2 indicates SGID bitset. 7 for full permissions for owner, 5 for write and execute permissions for group, and 0 no permissions for others.

6. Assign StickyBit toa directory : #mkdir csedir # chmod o+t /home/csedir OR # chmod +t /home/csedir # chmod 1757 /home/csedir 1 indicates Sticky Bit set, 7 for full permissions for owner, 5 for read and execute permissions for group, and 7 full permissions for others. Check using #ls –l csedir #ls –ld csedir