Web Administration

1. Web Administration Introduction to Linux

2. Linux – The Basics • Core component  Kernel • Kernel along with supporting function libraries  written in C • Different software apps modify appearance but all kernels are common to all distributions • Kernel is directly responsible for controlling the hardware (via device drivers)

3. Kernel Cont’d • Upgrade kernel  • Take advantage of new technologies • Fix problems • www.kernel.org • www.opensource.org Kernel is small – performs faster due to less code for the processor to analyze. Developed first by Linus Torvalds.

4. More Sites • www.linuxdoc.org • LUG Linux Users Groups (local to area) • www.gnu.org

5. Linux Basics Cont’d • Package Manager  Red Hat  RPM’s • Tarball  compressed archive of files like zipped files • Linux iso’s downloaded from: • www.linuxiso.org

6. Common Uses • Internet servers • File & Print servers • Application servers • Super computers • Scientific / Engineering workstations • Office workstations

7. Internet Server • Hundreds of network services that provide the framework for an internet server. • Mail services • Routing • FTP services • Firewalls & Proxy services • Web services • News services • DNS services

8. Mail Services • E-mail is distributed via a network of e-mail servers,  mail transfer agents (MTA’s). • Sendmail, postfix, smail, and qmail. • An MDA (Mail Delivery Agent) downloads from the MTA for the user • Procmail, fetchmail • MUA (Mail User Agent)  user views e-mail • Mutt, pine, printmail, elm, mail, Netscape, Eudora

9. Routing • A core service that is necessary for the Internet to function. • Internet  a large network of interconnected smaller networks. • Router provides interconnect – it contains information regarding the structure of the Internet  sends this info from one network to another. • Linux is a good choice for routers: Linux router Project  www.linuxrouter.org

10. FTP Services • Most common and efficient method for transferring files over Internet. • File Transfer Protocol • Keep updated – security issues • www.wu-ftpd.org

11. Firewalls & Proxy Services • Firewalls are placed between network and connection to the internet. • Linux has firewall support built directly into the kernel; utilities  ipchains and netfilter/iptables used to configure rules. • netfilter.samba.org

12. Proxy Services • Requests Internet resources such as URL’s and FTP sites on behalf of the internal computers. • Keep track of the information passed to the client by maintaining a Network Address Translation (NAT) table. • Common linux proxy server is Squid. • www.squid-cache.org

13. Web Services • Internet browser • Basic level – web server is just a server using HTTP  provide information. • However – they can process programs • CGI/ Perl scripts, PHP scripts • SSL (Secure Socket Layer) is a method for communicating with encrypted material. • www.apache.org

14. DNS Services • Uniquely identified computers – IP address is assigned. 204.26.82.3 • DNS translates URL’s or FQDN such as www.linux.org into an IP address. • BIND (Berkely Internet Name Daemon) • www.isc.org

15. Typical Install Partitions /boot -> contains Linux kernel and boot files -> 50MB /home -> User home dir’s ->200 MB / user /usr -> System commands and utilities -> ~ 2GB /usr/local -> Location of add programs -> ~4GB /opt -> Alternate location of add programs -> ~4GB /var -> Logs and spools -> 2GB /tmp -> Temp files created by programs -> 500MB Swap -> typically twice installed RAM

16. Filesystem • Linux supports over 50 different filesystems. • ext2 is traditional filesystem used on most Linux systems. • Ext3 and REISER are much more robust as they perform a function called journaling. • A journaling filesystem is one that keeps track of the information written to the hard drive in a journal.

17. Boot Loader • Is a program started by the BIOS ROM after POST, which loads the Linux kernel into memory. • Can also be used to load other OS’s. • Two types: • LILO (LInux LOader) • GRUB (GRand Unified Bootloader

18. Basic Linux Usage • Recall that an OS is merely a collection of software that allows you to use the system hardware in a meaningful fashion. • Kernel in Linux is simply a file called “vmlinux” • There must exist a channel that allows a certain user to communicate with the kernel. • In Linux, called a terminal – allows login access. • Putty – ssh into our box from outside this lab

19. Shell • Once logged in the basic user interface is a shell – accepts input from user and passes into the kernel for processing. • Default shell – BASH shell (Bourne Again Shell) • It interprets all info the user enters onto the command line. • Commands indicate the name of the program to execute and are case sensitive.

20. Basic Shell Commands • Options are specific letters that start with a dash “_” appear after the command name and alter the way the command works. • Arguments do not start with a dash. Specify parameters that the command works upon.

21. Common Commands clear clears terminal screen reset resets to default terminal settings Finger displays info on system users who displays current logged on users whoami displays your login name id displays the number associated with your user acct name date current date and time cal dispalys calendar for the current month exit exits the shell

22. Help • Linux contains manual pages that help you gather information about any command. • Can be accessed with man “command” • Command for shutdown: • shutdown –h now • halt • reboot