Unix Notes

1
Unix Notes

• System Administration

13
2
Basic System Admin Tasks (As Before)

• Account Management (add, delete, change
  passwords)
• Startup and Shutdown
• Monitor System
• Disk Administration
• Memory Management
• Security and Backups
• Job Management
• Networking
• Install/Upgrade Hardware and Software
• Services Management (email, web, etc..)
• Etc. Same list as with Windows Admin.

3
Basic Installation Steps

• Have 3 Red Hat Linux CD (no boot floppy disk)
• Reboot System off of the CD
• Select Language, Keyboard and Mouse configuration
• (taking defaults often works best, since linux
  probes the hardware for correct defaults)

4
More Installation .

• Disk Partitioning
• Choose Boot Loader
• Network Configuration (hostname, ip address,
  subnet mask, default gateway, dhcp, dns, etc..)
• Firewall Configuration
• Time Zone selection

5
And more installation..

• Set root password (root is the unix
  administrators account)
• Pick software packages to install
• Formatting of Hard drive Occurs
• Installation of software Occurs from CD to hard
  drive
• Create boot disk?
• Configure monitor and graphics card

6
Last Installation Slide

• Reboot
• Setup User Accounts
• Set Date and Time
• Finished!
• (you can now sign on as root or any other
• account you created above)

7
Account Creation/Deletion

• Manual
• Edit /etc/passwd, /etc/shadow (if it exits),
  /etc/group (maybe)
• Create home directory (mkdir /home/smith)
• Set password (passwd)
• Copy config files to account, from /etc/skel
  (like .cshrc, .login, .emacs, etc..)
• Check permissions (chmod), ownership (chown) and
  group (chgrp)

8

• To delete reverse the above, remove entries from
  /etc/passwd, /etc/shadow and /etc/group. Erase
  home directory and files within. Erase mail
  spool area (/var/spool/mail).

9
Gui Tools

• Solaris - admintool
• Linux - (linuxconf under RedHat linux 5.x)
• User Manager under RedHat Linux 7.x
• Start ? System Settings ? Users and Groups (
  Under RedHat Linux 9)

10

• /etc/passwd file - one line per account (user and
  system accounts)
• fields separated by colons
• username (1-8 characters)
• password - encrypted
• uid - user id number, integer
• gid - group id number, integer, related to
  /etc/group
• general info field
• home directory
• shell (/bin/sh /bin/bash /bin/csh /bin/tcsh)

11
example (from clam)

• trleex7104842000Tracey Lee/clam/u2/students/
  trlee/bin/tcsh
• jlamelasx7104942000joselamelas/clam/u2/studen
  ts/jlamelas/bin/tcsh
• traceypx7105042000Tracey Pino/clam/u2/student
  s/traceyp/bin/tcsh
• pwconv - tool to convert /etc/passwd to
  passwd/shadow combo

12

• /etc/shadow file - one line per account (user and
  system accounts)
• fields separated by colons
• username (1-8 characters)
• Encrypted password
• other misc. fields (may not be used), mainly for
  password/account expiration
• Ex
• smithZZ/rpaXz!2wi.Cw
• stanab2393.!xy!!.CW3

13

• /etc/group file - one line per group name
• fields separated by colons
• Groupname (1-8 characters)
• Optional group password (not often used)
• Group ID number (integer number)
• List of users in the group (comma separated)
• Ex.
• root0root,adm
• sys3root
• staff1000stan,megan,rachel
• users2000nixon,carter,bush,clinton,washington

14
Basic unix commands

• date
• cp file1 file2
• mv file1 file2
• mv file1 directory1
• vi filename
• emacs filename
• pico filename
• more filename
• cat filename
• chown username file
• chgrp groupname file
• chmod ugorwx filename
• echo PATH

• ls
• ls -lg
• man ls
• pwd
• cd
• cd ..
• cd .
• cd /usr/ local
• passwd
• mkdir directoryname
• rmdir directoryname
• rm filename

15

• start-up-files (in ones account)
• .login .cshrc .bashrc .xinitrc .emacs
  etc..
• (use ls al to see all files, even hidden/.dot
  files)

16
3. File System/Partitions

• Typical Partitions
• / (root, contains everything that is not in the
  other partitions, like /etc /dev etc..)
• /usr (system files)
• /var (log files and spool area)
• /home (home directories)
• Other partitions partitions particular to linux
• /boot (boot info)
• /services (for email, web, and other services)
• swap (swap space)

17

• Can have more partitions, or less (at least 2 are
  needed, swap and root). The above is typical.
• Each of the above is associated with a partition
  on the hard drive, like /dev/hda1 /dev/hda2
  and can be seen with "df" or "mount" or look at
  the contents of /etc/fstab.

18
Df and Mount commands

• df (Disk Free)
• On clam (df k)
• Filesystem kbytes used avail capacity
  Mounted
• /dev/hda1 962571 437769 467048 49 /
• /dev/hda2 . . . 80
  /usr
• /dev/hda3 . . . 21
  /var
• /dev/hdb1 . . . 63
  /home
• Etc

19
DF and Mount Commands

• mount
• / on /dev/hda1 read/write/logging on 3/1/04
  740am
• /usr on /dev/hda2 read/write/logging on 3/1/04
  740am
• /var on /dev/hda3 read/write/logging on 3/1/04
  740am
• /home on /dev/hdb1 read/write on 3/1/04 741am
• /test on /dev/hdb3 read on 3/10/04 1100am
• Etc

20
Processes (jobs)

• ps (just view your own jobs)
• ps -ax more (all system jobs)
• ps -aux more
• kill job
• kill -9 job (sure kill)
• top (tool to watch the top N jobs running)

21
PS Command

• ps ax
• PID S (status) Time Command
• 1 S 440
  init
• 2 S 120
  pageout
• 252 R 030 named
• 292 S 120 cron
• 300 S 110 lpd
• 1253 R 020 ./hw1

22
PS Command

• ps ax
• PID S (status) Time Command
• 1 S 440 init
• 2 S 120 pageout
• 252 R 030 named
• 292 S 120 cron
• 300 S 110 lpd
• 1253 R 020 ./hw1

23
PS Command

• ps aux
• User PID CPU MEM Start Time Command
• smith 569 5 3 800am 345
  a.out
• root 204 1 1 630am 030
  backup
• mrpig 1000 50 60 200am 833 test

24
Booting/Shutdown

• boot disk
• LILO (linux linker loader), useful for
  multibooting/dual booting
• Grub (another boot loader)
• Above not needed with Solaris on a Sun
  workstation...a pc/linux thing.

25
Meg

• login - name/passwd at the username prompt
• logout - logout or control-d or by selecting
  logoff from the lower-left button (and can also
  shutdown system from here)

26
Shutdown

• shutdown now go to single user mode
• shutdown -h now halt (firmware level)
• shutdown -r now reboot
• reboot
• halt
• (see man shutdown)

27
Run Levels

• run level
• 0 - halt (firmware)
• 1 - single user mode
• 3 - multi user mode
• 5 - multi user with xdm
• 6 reboot
• Can be viewed in /etc/inittab
• id3initdefault (default bootup mode)
• init 0 similar to halt or shutdown -h
• init 6 similar to reboot or shutdown r
• (see man inittab)

28
StartUp Scripts

• /etc/rc.d/rc0.d
• rc1.d
• rc2.d
• ...
• rc6.d
• --gt K10xxx
• or S10xxx
• Each specific job/daemon that must startup at
  boot time and stay running all the time, has a K
  and S file in one of the above startup areas.
  Like cron /etc/rc.d/rc3.d/S40cron
• K40crond
• K scripts Kill scripts S scripts Start
  scripts

29
X windows

• Gui interface created by MIT in the mid 80s (pre
  windows days)
• Linux - runs version called Xfree

30
Pearls of Wisdom

• Security Issues 1. Permissions
• BIG 3 2. Ownership
• 3. Group
• Good SysAdmin 1. Testing
• BIG 3 2. Documentation
• 3. Communication

31
Unix

• job/processes/daemons startup and run
• /etc/rc scripts (S and K scripts, run at bootup)
• /etc/inetd.conf (started by inetd daemon) (also
  called xinetd daemon and /etc/xinetd.conf)
• cron (job scheduler)

32
THE END