Linux Administration

Pre-Install

• Different distributions – Redhat, Caldera, mandrake, SuSE, FreeBSD

• Redhat Server Install– Check HCL– Significant issues

• Stability, availability and performance• Avoid games, casual users, anonymous ftp, telnet• Allow access via secure shell, secure ftp and

firewall policies• Avoid Xwindows unless needed by user at console• Watch out - runaway daemons will eat your cpu

More pre-install options• Dual-booting

– Need separate partitions for all OS you plan to run• Fips.exe for repartitioning FAT• Install windows First, Linux afterwards

• Install Options– CDRom (boot.img) or over the net (bootnet.img)

• If install fails – Kernel panic

• You don’t need to panic !• Its almost always Hardware issues.

– Check cdrom for CRC errors– Check HCL

Installation

• Boot.img– For CDROM install

• Type text for text based screen• Hit enter for GUI based (If video card is pretty

decent)

– Select language, keyboard and mouse• To Reconfigure

– /usr/sbin/kbdconfig (keyboard) /usr/sbin/mouseconfig (mouse)

Creating Partitions• Partitions are mounted at boot time • / is the root directory• Common partitions

– /usr • For program files

– /home• Home directories for users

– /var• Log files and system messages

– /tmp• Temporary files. Monitor to avoid, filling up the entire hd

– Swap• Not a file-system. Used as virtual storage and paging• Double the RAM if less 128Mb or same as RAM is more

than 128Mb.

Boot Manager• Handles the actual load process of the OS

– Same as NTLDR (windows NT)– LILO– GRUB

• Where to setup the boot manager ?– MBR (Master Boot Record)

• BIOS uses POST for hardware checking and passes control to MBR.

• The software in MBR is loaded– First sector of the boot partition

• Select this if you are using another boot loader– Preferred boot loader runs first and passes control to

LILO/GRUB if you decide to start linux.

• LBA (Logical Block Addressing): – Used by SCSI devices

Network Config and User List

• Ethernet cards are numbered– eth0, eth1, eth2– Configurable as DHCP or static

• User list– /etc/passwd

• Cannot login unless the user has an entry• NIS for remote user authentication

– /etc/shadow• Encrypted passwd file• Supports long passwords – upto 256 char• Supports different encryptions

– MD5, blowfish

Configuring X• X Windows:

– Basis of linux gui– Communicates with the actual video hardware.– Numerous programs that use X

• KDE, GNOME, Enlightenment, Sawfish– Decoupled from the base OS

• Possible to load OS with out starting the GUI• Saves memory and system resources

– Xorg• Version of X used by linux.

– Xfree86 (older version)• Auto detects video card and monitor• Manual configuration if card is not identified

– Requires user to know frequency monitor, refresh rates, memory on video card.

Common Commands• #linuxconf &

– For most administrative tasks• Manage users, passwords, network configurations, devices

• #ps –ef | grep more– See all running processes.

• #kill – Kill a running process (kill -9 254)

• #man– Documentation (man ls)

• #ls (folder, file listing)• #chgrp (change group)• #chown (change ownership)- p:384 for permissions

• #gzip, #tar (to compress files)• #du (disk utilization)

Useful Commands

• Su (switch user)– Change user

• Uptime– Tells how long the system has been up.

• Xconfigurator (redhat 8 or lower)– redhat-config-xfree86 (redhat 9)– Configure display

• Mouseconfig– Configure mouse

• Setup– Fire wall, ports, display manager, audio