1. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
Lecture 1
Security & permissions commands
Date: MON 18/03/1432
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

2. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
Umask(User Mask
Umask abbreviation of user mask
Is a command to set the file mode creation mask
(Umask) sets the file-creation permissions
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

3. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
Umask(User Mask
Symbolic mask:
Umask -S
displays the existing default value for new files
For example the result of the last command may be like:
u=rwx,g=rwx,o=rx
This means creating new files with the mode:
-rw-rw-r--
And directories with the mode:
Drwxrwxr- x
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

4. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
Umask(User Mask
Notes:
r:read
w:write
X:excute
u:user
g:group
o:other
r=4
w=2
x=1
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

5. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
Umask(User Mask
Octal mask:
666 in the case of files,
777 in the case of directories.
The octal notation is as follows:
0 – read, write and execute
1 – read and write
2 – read and execute
3 – read only
4 – write and execute
5 – write only
6 – execute only
7 – no permissions
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

6. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
Umask(User Mask
(Umask 022)
causes files to be created with permissions of 644 (rw-r--r--) ,
and directories to be created with permissions of 755 (rwxr-xr-x
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

7. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
Umask(User Mask
022 (masking out the write permission for the group and others), which ensures that new files are only writable for the owner (i.e. the user who created them).
Another common value is 002, which leaves the write permission for the file's group enabled. This can be used for files in shared workspaces, where several users work with the same files
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

8. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
Umask(User Mask
umask 0174 mkdir foo touch bar ls -l drw-----wx 2 dave dave 512 Sep 1 20:59 foo -rw----w- 1 dave dave 0 Sep 1 20:59 bar
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

9. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chmod (change mode)
(chmod) set permissions (modes) of files or directories
Chmod +rwx file-name
To add read write and execute for all
Chmod -rwx file-name
To remove read write and execute from all
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

10. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chmod (change mode)
Change mode of MYFILE to -rw-rw-r--
chmod 664 myfile
ls -l myfile
-rw-rw-r Jul 3 10:13 myfile
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

11. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chmod (change mode)
Add the read and write permissions to the user and group classes of a directory:
chmod ug+rw mydir
ls -ld mydir
drw-rw unixguy uguys 96 Dec 8 12:53 mydir
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

12. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chmod (change mode)
remove write permissions for all classes:
chmod a-w myfile
ls -l myfile
-r-xr-xr-x 2 unixguy uguys 96 Dec 8 12:53 myfile
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

13. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chmod (change mode)
Set the permissions for the user and the group to read and execute only (no write permission) on mydir:
chmod ug=rx mydir
ls -ld mydir
dr-xr-x--- 2 unixguy uguys 96 Dec 8 12:53 mydir
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

14. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chgrp(change group)
(chgrp) changes group associated with file.
chgrp group files Or
chgrp -R group files .
Note:
Can be used to change the group associated with subdirectories and files of a directory.
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

15. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chgrp(change group)
ls -l fu -rw-r--r-- 1 amani amani 545 Nov fu chgrp work fu -rw-r--r-- 1 amani work 545 Nov fu
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

16. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chown(change owner)
chown - changes ownership of a file.
(chown userid files )
or:
chown -R userid files
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

17. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
chown(change owner)
chown root fu ls –l fu -rwxrwx--- 1 root work 0 Sep 27 19:30 fu
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel

18. Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel
End
Ustaza. Imtithal Alnour Saeed & Ustaza Sana AL-Hwishel