User Management

Question 1

useradd

Answer 1

• c: comments
• G: add supplementary group
• g: add primary group
• m: home directory
• s: default shell

Question 2

passwd

Answer 2

-e: expire after use

Question 3

userdel

Answer 3

-r: remove home directory

Question 4

groups

Answer 4

Shows user what primary and secondary groups members of.

Question 5

groupadd

Answer 5

Add system group

Remove with groupdel

Question 6

/etc/passwd

Answer 6

Flat file database with info on users and system accounts.
Format is: user, password field ( x=encryption in /etc/shadow ) , uid, bid, uid info, full home path, comment for account, directory path for shell.

Question 7

/etc/shadow

Answer 7

Similar layout to passwd.
User, encrypted password, days since J1:1970 password changed, min # days password valid, days may change password, days warning, days inactive following expire, day account expires.
Note: encryption can be identified within salt.
$1$=MD5
$2a$=Blowfish
$2y$=Blowfish
$5$=SHA256
$6$=SHA512

Question 8

/etc/group

Answer 8

UID, password status, gid , other used in.

Question 9

/etc/skeleton

Answer 9

Contains items automatically added to new user’s home directory when account created.

Question 10

/etc/default/useradd

Answer 10

Config file referenced by useradd when new user acct created. Includes GROUP, HOME, INACTIVE, EXPRE, SHELL, SKEL, CREATE_MAIL, SPOOL.

Question 11

getent

Answer 11

Query database for info about user/group.

Can see: group, passwd

Question 12

usermod

Answer 12

Modify user account settings.

• a: add
• d: home directory
• G: secondary group
• L: lock login
• s: shell file
• U: unlock login

Question 13

change

Answer 13

List and modify aging parameters of user passwd.

• E : expire. Ex: -E 2019-01-01
• l: list account settings
• W : amount of days to expire.

Question 14

groupmod

Answer 14

Modify attributes of existing groups

• g: set new GID
• n: set new name for group.