CPSC 665 Spring 2004 Basic System Administration

1. CPSC 665 Spring 2004Basic System Administration Nolan Flowers

2. Agenda • Operating Systems • Red Hat Linux • Solaris • Sources for information • O’reilly Books Unix Power Tools 2nd edition • Linux Administration Handbook

3. Topics Covered • Useful commands • Useful files • Installing software

4. Commands • find • ls • grep • ifconfig • netstat • chmod • chown • chgrp • adduser

5. find • The Syntax for find is:

6. ls • Action: • Command to list files • Syntax: • ls -<parameters> • Commonly user parameters are: • -al list all long format (includes files that start with .) • -l list long format (doesn’t include . Files) • -ald list all long format directories

7. grep • Action: • Searches on a regular expression • Syntax: • grep <pattern> • ls’ best friend • ls –al | grep filename • Accepts wildcards

8. ifconfig • Action: • Gives status on network interfaces • Syntax: • Ifconfig (-a for unix) • Returns MAC address, interface status, netmask, broadcast address, number of received and transmitted packets, etc

9. netstat • Action: • Gives network status • Syntax: • netstat -<parameter> • Commonly used parameters • -nr lists routing table • -at lists active internet connections

10. chmod • Action: • Changes permissions on files or directories • Syntax: • chmod mode file (chmod 777 thisfile)

11. chown • Action: • Changes ownership of files or directories • Syntax: • chwon owner file (chown bubba thisfile)

12. chgrp • Action: • Changes group ownership of a file or directory • Syntax: • chgrp groupname file (chgrp staff thisfile) • chown and chgrp can be aggragated: • chown user:group file (chown bubba:staff thisfile)

13. adduser • Action: • command to add users • Syntax: • usage: adduser [-u uid [-o]] [-g group] [-G group,...] • [-d home] [-s shell] [-c comment] [-m [-k template]] • [-f inactive] [-e expire ] [-p passwd] [-M] [-n] [-r] name

14. Important Files • /etc/password • /etc/shadow • /etc/group

15. /etc/password • Sample /etc/password file bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin adm:x:3:4:adm:/var/adm:/sbin/nologin • One line per user each with seven fields • login name • Encrypted password (x indicates use of shadow file) • UID number • Default GID number • Full Name • Home directory • Login shell

16. /etc/shadow • Sample /etc/shadow file bin:*:12333:0:99999:7::: daemon:*:12333:0:99999:7::: adm:*:12333:0:99999:7::: • One line per user each with nine fields • login name • Encrypted password • Date of last password change • Minimum number of days between password changes • Maximum “ • Number of days in advance to warn about password expiration • Number of days after expiration that account is disabled • Account expiration date • Reserve field that is always empty

17. /etc/group • Sample /etc/group file wheel:*:10:root,joe,jim,john csstaff:*:100:bubba,sissy students:*:200:kim • One line per group each with four fields • Group name • Encrypted password (historical) • GID number • List of members, separated by a comma with no spaces

18. Pitfalls & Cautions • Make sure the shell exists before modifying /etc/password • Don’t set UID to 0. Convenient, but a really bad idea. • Start group IDs higher than 100.

19. Installing Software • wget • tar -xvfz • Dependencies • configure • make • make install

20. wget • ftp, scp and http are methods of transfering data. • wget <link> establishes the connection and transfers the file in one easy step • Example: unix % wget http://mirror.ehpg.net/apache/httpd/httpd-2.0.48.tar.gz This will retrieve the apache source to your local directory

21. tar • Most, if not all files come either tar’d or gzip (compressed) or both. • tar has no compression it is just a bundleing of files for ease of transfer. • To untar and uncompress at the same time use: • tar xvfz <filename> • x: extract • v: vervose • f: file • z: unzip

22. Dependencies • A majority of software depends on other software to compile and run. • C is needed to compile the software (make) • To run https, pops or imaps you need ssl • To have php query databases, … etc. • Some package managers check dependencies and download them as needed.

23. Configure • Configure is where you pass parameters to fine-tune your installation of the software. • Common parameters are: • Location (ie directories) • Security (openssl) • What modules to include

24. make • This builds the program. • That is, make would be executed, it would look for the first target in Makefile and do what the instructions said. • The expected end result would be to build an executable program.

25. make install • This again invokes make. • make finds the target install in Makefile and follows the directions to install the program. • Voila! Your program is compiled and installed.

26. Installing Software • cd ./apache_1.3.29 • ./configure \ • --prefix=/usr/local/apache \ • --enable-module=so \ • --enable-module=rewrite \ • --enable-shared=rewrite \ • --enable-module=setenvif \ • . . . <parameters deleted for brevity> • --enable-shared=log_agent \ • --enable-module=headers \ • --enable-shared=headers • make • make install

27. Installing Software • When make doesn’t • Things to consider when make fails: • Bad download of source code • Wrong parameters passed in configure • Things to remember: • Verify the checksum • Always do a ‘make clean’ prior to trying again

28. Check the logs • When a program is not running as expected, the first place to look is the log files. • Log files either explicitly state the nature of the error or give excellent clues • If you compiled from source double check your dependencies. Since so many parameters can be passed to configure, errors are easy to make.

29. Class Listserv • Class Listserv • 665-04@listserv.tamu.edu • Questions specifically for gold team • Only gold and platinum teams have access to read these e-mails • 665-04-gold@listserv.tamu.edu