Unix%20System%20Administration

1
Unix System Administration

• Chapter 6
• Adding New Users

2
Bob Jane Adding Users

• Edit /etc/passwd ( /etc/shadow if necessary)
• Set the password using passwd command
• Create the users home directory
• Copy config files (dot files) to the home
  directory
• Setup any mail aliases

3
How Many Users Does It Take To Screw-Up Your
System?

• Add user to any secondary groups via /etc/group
• Record account info (paper)
• Enter user into site-wide database (e.g. LDAP)
• Configure disk quota
• verify account is setup correctly

4
Cant Unix People Spell?

• /etc/passwd format
• username (must be uniq)
• encrypted password (x if shadow used)
• userid (does not need to be uniq, 0-65535)
• groupid (primary group)
• gecos (comment or real name field)
• home directory location
• login shell (empty /bin/sh)

5
Everybody Has a Better Mousetrap

• Edit the password file using vipw or just vi
• Other utilities to ease account creation and
  management
• Most OSs have a utility to add users
• useradd/usermod/userdel (Linux, Solaris, )
• admintool (Solaris)
• smit or smitty (AIX)
• linuxconf (Linux)

6
Size Does Matter

• 64 (1 char
  password)
• 4,096 (2 char password)
• 262,144 (3 char password)
• 16,777,216 (4 char password)
• 1,073,741,824 (5 char password)
• 68,719,476,736 (6 char password)
• 4,398,046,511,104 (7 char password)
• 281,474,976,710,656 (8 char password)

7
So Long Sucker, Er, I Mean Alumni

• Removing a user
• backup all user info (below) first
• remove entries in /etc/passwd and /etc/shadow
• remove userid from /etc/group
• remove any entries in /etc/aliases
• remove mail spool file (INBOX)
• remove home directory

8
I Have The Power

• Setting quotas
• edquota username
• edquota -p protousername username
• Disabling account (but not removing)
• passwd -l username

9
Stop Your Web Browsing and Pay Attention!

• Name a possible problem with reusing UIDs.
• What/who is PAM?
• How many characters are actually used in the
  password?