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System Administration Basics

Session 3

By: Bahaa S. Salama (bahaa2008)

Agenda

Users Administration

Permissions

Partitions

Booting process

Processes

Applications

Networking Basics

Important Files

/etc/passwd/etc/shadow/etc/group/etc/gshadow

Users Administration

Add user useraddDelete user userdelModify user usermodChange/Set password passwdDisplay logged in users whoDisplay effective user whoamiDisplay real/effective id id

User Administration cont.

Who is login/what is he doing wCurrent logged in users usersMessage all users wallAdd groupgroupaddDelete groupgroupdelModify groupgroupmodGroups that I'm memer ingroups

Permissions

Why Permissions ?

User,Group,Other

Read,Write,Execute

Permissions symbolicallyr read u userw write g groupx execute o other

Permissions - cont.

Permissions numerically7 rwx 3 -wx6 rw- 2 -w-5 r-x 1 --x 4 r-- 0 ---

Change user chown

Change group chgrp

Change permissions chmod

Partitions Information

List Partition fdisk -l

Partion Editorfdisk /dev/sda-nadd new partition-d delete partition-llist partition -a add bootable flag

Disk space

File System usage df

File Space usage du-s summerize-h human readable

Mounting Partitions

List current mounts mount

Mount partitionsmount -t fstype -o options device dir

Examplesmount -t vfat /dev/sda1 /media/sda1

Unmount umount device umount /dev/sda1

/etc/fstab

File Syntax

UUID vs devices

Processes Management

List processes ps aux

Kill processkill by pid kill -9 pidkill by namekillall prog_name

Processes treepstree

Top processestop

Boot Process

BIOS - Boot Sequence

Stage 1 bootloader (MBR)

Stage 2 bootloader (Grub,LILO, etc)

Kernal (linux kernel)

Init (starting userspace applications)

Boot loader

Grub Installation

/boot/grub/menu.lst

Splash screen

Timeout

Default option

Other Systems

Kernel && init

Init Runlevels

0 halt1 single-user mode3multi-user mode5 multi-user mode + X-based login screen6 reboot

Init Scripts

Understanding init scripts

/etc/init.d/

How to use init scriptsStart

Stop

Restart

Reload

Status

Installing Applications

Installation MethodsFrom source

Using Package mangers

Using Package utilites

Installing from source

Get the source

Get dependencies

Installing dependencies

Installing the application

Installation Process./configure && make && make install

Uninstallation Processmake uninstall && make clean

Package Managers

/etc/apt/sources.list

/etc/apt/sources.list.d/

Apt-get-install -remove-purge

Apt-cache-search

Package Utilities

dpkg-i install .deb package-r remove .deb package-l list installed packages--reconfigure reconfigure package

Configuring Network Interface

Display interfaces ifconfig -aSet ip manuallyifconfig eth0 Get ip automatic dhclient eth0Set default route route add def gw eth0 Set wireless ap iwconfig eth1 essid Set DNS Servers in /etc/resolv.conf (demo)

Questions

Thanks

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