RHCSA Ch6

Question 1

change owner of a file

Answer 1

chown user1 file.txt

Question 2

change group owner of a file

Answer 2

chown :accounting file.txt

Question 3

Change user and group owners

Answer 3

chown user1:accounting file.txt

Question 4

what are the values of rwx

Answer 4

r = 4
w = 2
x = 1

Question 5

give user rwx, group rx, and other no permission - numeric and symbolic

Answer 5

chmod 750 file.txt

chmod u=rwx,g=rx,o= file.txt

Question 6

giver user rwx using symbolic permissions

Answer 6

chmod u+rwx file.txt

Question 7

take away execute from all users

Answer 7

chmod ugo-x file.txt
chmod a-x file.txt
a=all

Question 8

explain umask

Answer 8

umask
default is 0022
default perms for directories are 777. Subtract 022 from 777 = 755 (rwx,rx,rx)
default perms for files is 666. Subtract 022 from 666 = 644 (rw,r,r)

Question 9

changed umask

Answer 9

umask 0002 = only good for current session
To make persistent, edit ~/.bashrc and type umask 0002
To change system wide, edit /etc/profile.d/umask.sh
- if [ “$UID” -ge 1000 ] ;then
umask 0002
fi
^ for any user with an ID of 1000 or greater, their umask will be 0002

Question 10

set the SUID bit on a file

Answer 10

sudo chmod 4755 /usr/bin/su

sudo chmod u+s /usr/bin/su

Question 11

set the SGID bit to a file

Answer 11

chmod 2755 /usr/bin/screen
chmod g+s /usr/bin/screen
any file created in screen directory, will be own by that group

Question 12

search for SUID and SGID set

Answer 12

SUID
find / -perm -4000
SGID
find / -perm -2000

Question 13

What is the sticky bit

Answer 13

Makes sure that other users cannot move or delete a file in a directory with the sticky bit set

Question 14

how do you set the sticky bit

Answer 14

chmod 1777 stickydirectory

Question 15

list acl of a file

Answer 15

getfacl file.txt

Question 16

create a ACL for a user on a file

Answer 16

setfacl -m user:: file.txt
setfacl -m user:bob:rwx /home/file.txt
setfacl -m u:bob:rwx /home/file.txt
-m = modify

Question 17

create ACL for a group on a file

Answer 17

setfacl -m group:accounting:rx file.txt

setfacl -m g:accounting:rx file.txt

Question 18

set ACL for a user and group in one command

Answer 18

setfacl -m u:bob:rwx,g:accounting:rx file.txt

Question 19

create ACL for directory

Answer 19

setfacl -R -m user:bob:rwx /home/bob

-R = for files that currently exist in the directory

Question 20

set default acl on directory

Answer 20

sudo setfacl -d -m user:bob:rwx dir1

ensures that new files will grant bob rwx

Question 21

What are the three different options to delete and ACL

Answer 21

• x Remove specific acl
• k Remove all default acl
• b remove all acl