1. Chapter 15 System Administration By C. Shing ITEC Dept Radford University

2. Objectives Understand system administrator’s duty Understand the system start up and shutdown procedures Understand how to maintain file systems and user accounts Understand how to install software and peripheral devices Understand how to configure kernel Understand how to manage system accounting and security

3. System Admin Duty Boot up and shutdown systems Maintain and back up system Maintain user accounts and system accounting Install system and application software Install and configure peripheral and kernel Maintain network interface and system security

4. System Admin Account Root: user ID is 0 –Hard to correct problems if made mistake Become superuser: use su utility to create a child shell of root –sudo: provide special privilege for a specific task

5. System Start up Power up self test Load kernel to RAM Kernel start running and initialize itself Kernel starts first process PID=1(init), then it spawns child processes (getty) for creating and maintaining login shell using /etc/inittab to decide runlevels –Run fsck to check file systems (use sync utility to fix damaged file systems) –Mount file systems use mount for entries in /etc/vfstab file –Start daemons

6. System Run Level (Mode) BSD system in either of the 2 modes: –Single-user: create a Bourne shell Only / is mounted automatically Need manually mount other file systems for system repair, back-up, kernel reconfiguration –Multi-user Start daemons by running boot up file /etc/rc Start locally maintained services by running boot up file /etc/rc.local Clear files in /tmp

7. System Run Level (Mode) (Cont.) BSD system in either of the 2 modes: –Multi-user (Cont.) Create getty processes for every terminal in /etc/ttytab file Start up network services, default mode Start login process by replacing getty process when detect login attempt Start up shell replaces login shell for successful login Store login username in /etc/utmp and login session in /var/adm/wtmp

8. System Run Level (Mode) (Cont.) BSD system in either of the 2 modes: –Multi-user (Cont.) Logout: init process receives SIGCHLD signal – remove username in /etc/utmp and logout session in /var/adm/wtmp –Create a new getty process for the freed terminal

9. System Run Level (Mode) (Cont.) System V in either of the 8 levels: –0-6: can have own boot-up script for each level 0 : firmware 1 or S: for Single-user mode 2: muti-user, no network 3: multi-user, network 4: not used 5: shutdown for power off 6: reboot

10. System Run Level (Mode) (Cont.) System V in either of the 8 levels: –Boot-up files are /etc/rc0, /etc/rc1,…, /etc/rc6, /etc/rcS –Run level scripts are in /etc/rc0.d, /etc/rc1.d, …, /etc/rc3.d, /etc/rcS.d Start up script: name begins with S Shutdown script: name begins with K –All process management scripts are in /etc/init.d directory

11. System Shutdown shutdown –option time [message] –Option: h – halt r – reboot –Time: now – shutdown immediately +minutes – within minutes hours:minutes – within hours and minutes Example: shutdown –h now

12. System Shutdown (Cont.) halt reboot sync update super-block

13. Maintain File System fsck –p [filesystem] –Automatically correct inconsistency on filesystem Free block also inode Used block but not inode More than 1 inodes reference 1 block Wrong block number Wrong inode link count Inode not in any directory

14. Maintain File System (Cont.) df -k [filesystem] –Report in 1K block the disk space used/available for the mounted filesystem Example: df -k

15. Maintain File System (Cont.) du -option [filename] –Option: k – 1K block s – size only –Report in 1K block the disk usage for the filename recursively down to subdirectories Example: du –k.

16. Maintain File System (Cont.) quota [-v] [username] –Display [username’s] disk quota Example: quota

17. Maintain File System (Cont.) format [-d diskname] [-p partition] –Format partition on diskname Disk partition rule: –Swap space: 2 to 2.5 * RAM size –Partitions needed: /, /usr, /var, /tmp, /export through NFS, /opt

18. Maintain File System (Cont.) Red Hat server partition recommendation: (128 MB RAM) –/: 256 MB –Swap: 256 MB –/usr: 512 MB + –/boot: 16 MB –/home: user accounts: 512 MB + –/var: server log for a long time –/tmp or link to /var/tmp Note: combine partition space if not needed

19. Maintain File System (Cont.) Red Hat client partition recommendation: (32 MB RAM) –Swap: 64 MB –/boot: 16 MB –/: rest

20. Maintain File System (Cont.) Solaris server partition recommendation: (Dedicated server) –/ –Swap –/usr: shared system files –/opt: larger for NFS service –/export –/export/home: holds user accounts –/export/swap: for serve diskless client –/var: server log for a long time –/tmp or link to /var/tmp Note: combine partition space if not needed

21. Maintain File System (Cont.) Solaris client partition recommendation: –/ –Swap –/usr –/opt: if local optional software used –/var: client log for a long time –/tmp: if user or application use this a lot –/home: if workstation contains user accounts Note: combine partition space if not needed

22. Maintain File System (Cont.) mkfs newfilesystem [sectornumber] –Create a newfilesystem (with sectornumber sectors) newfs newfilesystem devicetype –Invoke mkfs using sectornumber specified by the devicetype in /etc/device.tab

23. Manage User Accounts Add user entry in /etc/shadow and /etc/passwd files –Use vipw command to edit –Change password using passwd command Add group entry in /etc/group file Create home directory for the user –Set up owner, group and directory permissions Provide start up files –.login and.cshrc files for start-up tc shell

24. Install Software & Configure Kernel Deposit/Download software in appropriate directory –Solaris: under / /kernel: Unix kernel (e.g. /kernel/genunix has about 1.5 MB) /bin, /usr/bin: Unix utilities, built-in commands /sbin: system binaries /dev: device files /lib: essential libraries /usr/lib: libraries for C, FORTRAN, … etc /var/log: log files /var/adm: admin log files

25. Install Software & Configure Kernel (Cont.) Deposit/Download software in appropriate directory –Solaris: under / (Cont.) /etc: admin files, start-up files, configuration files /opt: optional system software /proc: pseudo file systems, contains managing process information –User application: under /usr/local, often a mount point for other file systems /usr/local/bin: local software binary

26. Install Software & Configure Kernel (Cont.) Modify configuration file for your environment Use config utility to recompile kernel and create makefile for the architecture if not provided Run make utility to produce executable file for the software Reboot the system

27. Install Software & Configure Kernel (Cont.) Example: Install Kerberos 5 On Red Hat Linux –cd /usr/local/bin –mkdir kerberos; cd kerberos –Now, download Kerberos 5 from web –tar -xzf krb5-1.3.1.tar.gz This uncompress and untar the file –./configure --without-krb4 This recompiles kernel and create a makefile to exclude Kerberos 4 support – make This compiles necessary system files for Kerberos 5 – make install This creates executables and puts them in the right directories

28. Install Peripheral Devices Install device driver Find major and minor number of the device Associate the device with device driver –mknod devicename option majornumber minornumber Option: b – block device c – character device

29. Install Peripheral Devices (Cont.) Example: –mknod /dev/disk1 b 4 0 disk is a block device

30. Install Peripheral Devices (Cont.) Terminal files: –/etc/termcap (/etc/terminfo): complete terminal information –/etc/ttydefs: define terminal baud rate

31. Manage Network Devices ifconfig utility to configure network interface –Ifconfig interfacename ip-address netmask [up/down] assign ip-address to interfacename and running/shutdown Route utility to manually manage routing table –route add/delete ip-address netmask gateway create/delete an entry to ip-address in the routing table

32. Manage Network Devices (Cont.) netstat -r display routing table

33. Manage System Accounting and Security acct –Display accounting information –System usages store in /etc/adm/acct directory, use sa utility –Login/logout information stored in /usr/adm/wtmp file, use ac and last utilities

34. Manage System Accounting and Security (Cont.) Security –Disable unused ports –Disable commands/methods that avoid password rlogin, rsh –Disable utilities with known security problem ping, finger –Do not log on root account unless necessary Logon your regular account and use su utility to get super- user privilege –Watch files with SUID and SGID set /tmp has sticky bit set: only owner can modify or delete files –Use secure protocols Use secure telnet to replace telnet

35. Misc. uname –a Prints system information dmesg Display system diagnostic information such as memory, devices

36. Reference Ch. 15 Ch. 2 & 3 of Nemeth etl.