1. LINUX SYSTEM ADMINISTRATION

2. SYS ADMIN TASKS Linux System Administration Setting the Run Level
System Services
User Management
Network Settings
Scheduling Jobs
Quota Management
Backup and Restore
Adding and Removing software/packages
Setting a Printer
Monitoring the system (general, logs)
Monitoring any specific services running. Eg. DNS, DHCP, Web, NIS, NPT, Proxy etc.

3. Init Runlevels Linux System Administration
The following runlevels are defined in Linux:
0 - halt (Do NOT set initdefault to this)
1 - Single user mode
2 - Multiuser, without Network (The same as 3, if
you do not have networking)
3 – Text Mode
4 - unused
5 – Graphical Mode
6 - reboot (Do NOT set initdefault to this)

4. Init Runlevels Desktop Configuration
The default runlevel for a system to boot to is configured in /etc/inittab.
id:5:initdefault:
In GUI: Applications  System Settings  Server Settings Services
Generally, Linux operates in runlevel 3 or 5.

5. Linux Services Linux System Administration
There are 113 deamons, Out of them, the following are most widely used:
apmd : Power Management
autofs : Automount services
crond : Periodic Command Scheduler
cups : Common Unix Printing System
dhcpd : The DHCP server
dovecot : IMAP (Internet Message Access Protocol) and POP3 (Post Office Protocol) server
gpm : Mouse
httpd : Apache Web server

6. Linux Services Linux System Administration
iptables : Kernel based Packet Filtering firewall
kudzu: Finds new Hardware
mysqld : MySQL server
named : BIND server
network : Networking
nfs : Network File Share
nfslock : NFS file locking
ntpd : NTP (Network Time Protocol) server
portmap : RPC (Remote Procedure Call) support
postgresql : The Postgresql Database Engine

7. Linux Services Linux System Administration
sendmail : Sendmail Mail Server
smb : Samba Network Services
snmpd : Simple Network Management Protocol
squid : Squid Proxy Server
sshd : Open SSH and SFTP server
syslog : System Logging
xinetd : Provides support for telnet, ftp, talk, tftp etc.
ypbind : NIS Server

9. Linux Services Linux System Administration
Start/Stop boot time services in /etc/rc.d/rc3.d or /etc/rc.d/rc5.d
All services startup scripts which start with S will start at boot time and all startup scripts which start with K will not start at boot time. The number after S or K is the priority.
K95kudzu
K96pcmcia
S56xinetd
S60vsftpd
Use
service <service name> start/stop/restart
to start, stop or restart a service from command line

10. Creating a new User Account
Linux System Administration
Creating a new User Account
Add an entry in /etc/passwd and /etc/shadow file (use next uid and suitable gid). You will have to create the user directory and assign a password to the user
Use useradd or adduser command to create a new user (useradd –g <group> -d <home directory> -c <comment> -s <shell> login-name)
Use groupadd to create a new group (groupadd group-name). You will have to assign a password (passwd login-name)
In GUI: Applications  System Settings  Users and Groups

12. Removing a User Account
Linux System Administration
Removing a User Account
Remove login id from /etc/passwd & /etc/shadow file and delete home directory
userdel –r <username>
Use GUI to Delete the user

13. Modifying Users Syntax: usermod [options] username
Options are pretty much identical to those of useradd
Also, -l to change the user’s login name
And –G to list additional groups to add user to

14. Group Management Group info housed in /etc/group
Similar to user management
groupadd
groupdel
groupmod

15. Finding User Information
finger <nama-user>
id <nama-user>
groups <namauser>
cat /etc/passwd

16. File for User Management
/etc/group
Group account information.
/etc/gshadow
Secure group account information.
/etc/login.defs
Shadow password suite configuration.
/etc/passwd
User account information.
/etc/shadow
Secure user account information.
BEIT Presentation

17. /etc/passwd File /etc/passwd Holds user account info
Linux System Administration
/etc/passwd File
/etc/passwd Holds user account info
Login name
User Id (uid)
Group Id (gid)
General Comment about the user
Home Directory
Shell

18. $ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/bin/sh bin:x:2:2:bin:/bin:/bin/sh sys:x:3:3:sys:/dev:/bin/sh sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/bin/sh man:x:6:12:man:/var/cache/man:/bin/sh lp:x:7:7:lp:/var/spool/lpd:/bin/sh mail:x:8:8:mail:/var/mail:/bin/sh news:x:9:9:news:/var/spool/news:/bin/sh uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
hplip:x:113:7:HPLIP system user,,,:/var/run/hplip:/bin/false gdm:x:114:120:Gnome Display Manager:/var/lib/gdm:/bin/false himanshu:x:1000:1001:Himanshu,,,:/home/himanshu:/bin/bash guest:x:1001:1003::/home/guest:/bin/sh

19. /etc/group File
This file has information regarding the various groups in the system, each line gives information about one group.

20. # cat /etc/group root:x:0:root bin:x:1:root,bin,daemon daemon:x:2:root,bin,daemon sys:x:3:root,bin,adm
adm:x:4:root,adm,daemon
tty:x:5:
disk:x:6:root
lp:x:7:daemon,lp
mem:x:8:
kmem:x:9:
mail:x:12:mail

21. /etc/shadow File Linux System Administration
/etc/shadow Contains the encrypted password information for users' accounts and optionally the password aging information.
/etc/gshadow : Contains the encrypted password information for groups' accounts and optionally the password aging information.
Contoh /etc/shadow:
ddouthitt:$6$QR3drPrQ$JLolPKyiVuXvea1F2IpbPx9F9PEV0s/IGcNCpm6ZrBA6AFDvwHPQG7EsTQHuUqxfCvlsuKRb.O7w5RLPyj8nS/:15119:0:99999:7:::

23. chage $ chage -l ddouthitt Last password change : May 25, 2011
Password expires : never
Password inactive : never
Account expires : never
Minimum number of days between password change : 0
Maximum number of days between password change : 99999
Number of days of warning before password expires : 7