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Unix Advanced File Permission

# chmod u + s < filename > SUID

# chmod g + s < file name> GUID

# chmod o + t <Dir Name> Sticky Bit

What is SUID ?

The common explanation given for SUID is, it is an advanced file permission SUID allows an user to execute a script as if the owner of the script is executing it.

Example for SUID is

#passwd

GUID bit is set on an executable. It runs with the permission its owner

To understand the concept about SGID

1. Create a group called online

2. Create a folder called training

3. Create 3 Users called John, Daniel & Joe

4. Add 3 users into the group called online

5. Change the group owner online for the folder training

6. Create a file or folders under the directory Online

7. Check the owner of the group for every folder & files

8. It is in the respective of User’s Group

9. Do delete a file or folder irrespective the owner of the group

10. Now set the GUID

         a. # chmod 2775 /training

         b. Check the SGID setting on the folder

11. Now do create the files & folders

12. Try to add one more user into the group

13. Test the ownership of the folder

14. Does inherit the ownership of the group for folders & files

15. So that what is SGID?

To understand the concept about Sticky Bit

1. Create a Folder called /alldata [ mkdir /alldata ]

2. # chmod 777 /alldata

3. Create a few folders and files from different User

4. Check the Ownership of the folder & file

5. Try remove folder & file from different User irrespective of the ownership since we have assigned the 777
     permission

6. Now apply the sticky bit concept for the folder

       a. # chmodt+o /alldata or # chmod 1777 /alldata

       b. Now create the folders & files Under the folder alldata

       c. Check the Ownership

       d. Try remove folder & file from different User irrespective of the ownership since we have assigned the 777
           permission

7. Now what do you understand the concept.

8. So that What is Stickbit ?

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