Download - Linux
In the name of god LINUX
red hat(centos)
Abolfazl Hashemi
Title
• What’s Linux?
• working with directories, files
• Using text editors like vi, vim
• Control on mount & un-mounting process
• File permissions & ownerships
• Linux installation & package management (yum, rpm, wget )
• process & threads
• Configure disk partitions
• Manage disk quota & create quota report
• Symbolic links, FHS
• Writing shell script
• Working with archive files
• System resource management
• Working with debuggers in Linux
• gpg command
• Introduction to network
• Security in linux
• Do automate tasks in Linux, cron job
• Configure & working with OpenSSH
• Working with tcpdump
• Configure web server
• Network configuration
Summary of Linux
• Linux clone of unix os
• Linux can run on small computer
• Open source os
• Distributed of Linux – Debian GNU/Linux
– Fedora Linux
– Gentoo Linux
– Libranet GNU/Linux
– Red Hat Linux
– Yellow Dog Linux
– …….
Kernel
Shell
User
bash tsh zsh
Graphic User Interface(GUI)
x86_64 i386
Installation
• Requirements
• Customize installation
• X configuration
• GUI: graphical user interface
• Install
• What is shell, terminal, virtual terminal, super terminal, konsole, tty.
• man, --help
working with directories, files, …
• Command line for directories
pwd: current working directory-> /root
cd: change working directory -> cd /etc/init.d
ls: list of directory, files, ... .
• ls –a: list of all directory,… .
• ls –l : list of all directory,... With details
mkdir: make directories -> mkdir test
working with directories, files, …(cont’d)
rm: remove file, directory, … .
rm –r: remove recursive ->rm –r file
mv: move file, directory, … .
mv /etc/test /var
cp: copy file, directory, … .
cp /etc/test /var
working with directories, files, …(cont’d)
echo: display a line of text
date: print or set the system date and time date –s: set time and date
more: filter and show text less: opposite of more head: output the first part of file
Head –n 5 /etc/init.d/netfs
tail: output the last part of file tail–n 5 /etc/init.d/netfs
alias: summary of commands that you now it alias ll=“ls –l”
: -> arg out to arg in
working with directories, files, …(cont’d)
Important files:
/
/etc
/var
/sbin
/bin
/dev
/usr
/home
/root
/proc
Exercise1
What is . ?
What is .. ?
Using text editors like vi, vim
vi & vim -> vi test.txt
vim: vi improved
command for vi: i -> insert
:w -> save
:q ->quit
:! ->force
:wq! ->save and quit with force
Using text editors like vi, vim(cont’d)
u بٍ حالت قبل بش می گشدد معادلCtrl+z
Ctrl+r بٍ حالت بعذ می سيد معادلCtrl+y
:r ٍتمام مته سا کپی ي بعذ بٍ مکان دلخًاٌ اضاف .می کىذ
xپاک کشدن کاساکتش. dwٍپاک کشدن کلم. ZZرخیشٌ کشدن ي خشيج. e:باصکشدن فایل جذیذ. :nسفته بٍ فایل بعذی کٍ دس حال تغییش است..
Ctrl+u باال بشدن مته يCtrl+e باال بشدن .صفحٍ
Ctrl+d پاییه بشدن مته يCtrl+y پاییه بشدن .صفحٍ
:e filename يیشایش فایل مًسد وظش. Ctrl+g اطالعاتی دس مًسد فایلی کٍ داخل آن
.َستیذ می دَذCtrl+} يCtrl+{ بٍ ابتذا ي اوتُای پاساگشاف
.می سيدJ باال بشدن خط َای پاییه محل مًسد وظش. H بٍ ايلیه خط می سيدL بٍ آخشیه خط می سيد. R بٍ مذ جایگزاسی می سيد. :s/search-text/replace-text/g فقط دس
می پشسذ gci/.خط مًسد وظش جایگزاسی می کىذبشای کل s%:.کٍ می خًاَی تغییش دَی یا خیش
g/start/s/text/rep:.خط َا اوجام می شًدقشاس می دَذ بٍ ششط repَستtextَشجایی کٍ
-start .:5,10s/searchششيع خط با text/replace-text/g جایگزاصی می کىذ اص
.12تا 5خط :3,9d سا پاک می کىذ 9تا خط 3اص خط .
:# سفته بٍ خط#
:5,10w filename سا دس فایل 10تا 5اص خط .مًسد وظش کپی می کىذ
v: سفته بٍ محیط يیژيیال
Using text editors like vi, vim(cont’d)
• :set remap Accept macros within macros
• :set report Indicates largest size of changes reported on status line
• :set ro Changes file type to "read only"
• :set scroll=n set n lines for CTRL-d and z
• :set sh=shell_path set shell escape (default is /bin/sh) to shell_path
• :set showmode Indicates input or replace mode at bottom
• :set slow Postpone display updates during inserts
• :set sm Show matching { or ( as ) or } is typed
• :set sw=n Sets shift width to n characters
• :set tags=x Path for files checked for tags (current directory included in default)
• :set term Prints terminal type
• :set terse Shorten messages with terse
• :set timeout Eliminates one-second time limit for macros
• :set tl=n Sets significance of tags beyond n characters (0 means all)
• :set ts=n Sets tab stops to n for text input
• :set wa Inhibits normal checks before write commands
• :set warn
• warn
• :set window=n Sets number of lines in a text window to n
• :set wm=n Sets automatic wraparound n spaces from right margin.
• :set ws Sets automatic wraparound n spaces from right margin.
Using text editors like vi, vim(cont’d)
• :set ai Turns on auto indentation
• :set all Prints all options to the screen
• :set ap Prints line after d c J m :s t u commands
• :set aw Automatic write on :n ! e# ^^ :rew ^} :tag
• :set bf Discards control characters from input
• :set dir=tmp Sets tmp to directory or buffer file
• :set eb Precedes error messages with a bell
• :set ed Precedes error messages with a bell
• :set ht= Sets terminal hardware tabs
• :set ic Ignores case when searching
• :set lisp Modifies brackets for Lisp
compatibility.
• :set list Shows tabs (^l) and end of line ($)
• :set magic Allows pattern matching with special characters
• :set mesg Allows others to send messages
• :set nooption Turns off option
• :set nu Shows line numbers
• :set opt Speeds output; eliminates automatic RETURN
• :set para= macro names that start paragraphs for { and } operators
• :set prompt Prompts for command input with :
• :set re Simulates smart terminal on dumb terminal
Using text editors like vi, vim(cont’d)
Exercise2
How to search word in text?
How to save output command in text?
What are grep and find command?
Using text editors like vi, vim(cont’d)
od: octal and other format
export: show variables
env: environments variable
wc: show word, char, … .
sort: sort text
uniq: delete repeated lines
pr: print text
touch: change file timestamps
cpio: copy files to and from archives
dd: convert and copy a file
Control on mount & un-mounting process
• mount: verify hardware(device) to Linux
• umount: unmount
• command for mount: mount -> show devices mounted
mount /dev/cdrom /mnt->mount cd rom
mount /dev/sda1 /mnt ->mount sda(storage device type a number1
mount –l –t <type> -> list and type of devices
/etc/udev/rules.d -> verify devices
Control on mount & un-mounting process(cont’d)
Important file:
/etc/fstab
/etc/mtab
/proc/mounts
Exercise3
What is mount point?
What is journaling?
File permissions & ownerships
d r-- r-- r-- = d 4 4 4 -> directory & permission is 444
- --- --- ---
- rwx rwx rwx -> read, write, execute
ll -> - --- --- ---
types are directory, link, … .
File permissions & ownerships(cont’d)
- Normal data file; may be text, an
executable program, graphics, compressed data, or just about any other type of data.
d Directory; disk directories are files
just like any others, but they contain filenames and pointers to disk in odes. Controlling Access to Files 195
l Symbolic link; the file contains the
name of another file or directory. When Linux accesses the symbolic link, it tries to read the linked-to file.
p Named pipe; a pipe enables two
running Linux programs to communicate with each other. One opens the pipe for reading, and the other opens it for writing, enabling data to be transferred between the
programs.
s Socket; a socket is similar to a
named pipe, but it permits network and bidirectional links.
b Block device; a file that
corresponds to a hardware device to and from which data is transferred in blocks of more than one byte. Disk devices (hard disks, floppies, CD-ROMs, and so on) are common block devices.
c Character device; a file that
corresponds to a hardware device to and from which data is transferred in units of one byte. Examples include parallel port, RS-232 serial port, and audio devices.
File permissions & ownerships(cont’d)
command for permission
chmod: change file mode -> chmod 777 filename
chown: change file owner and group-> chown user1 filename -> chown –R
Set User ID (SUID)
Set Group ID (SGID)
File permissions & ownerships(cont’d)
File permissions & ownerships(cont’d)
File permissions & ownerships(cont’d)
File permissions & ownerships(cont’d)
Command line:
groupadd: create new group -> groupadd test -p test
groupadd –r: create system group
groupdel: delete group
groupmems: add members to group ->groupmems –g test [-l] [-a] [-d]
groupmod: groupmod test –g 777
File permissions & ownerships(cont’d)
find / [-group name] [-user name]
newgrp: login to new group
useradd: create new user
Userdell: delete user
passwd: change password
File permissions & ownerships(cont’d)
Important directory: /etc/shadow
/etc/group
/etc/gshadow
/etc/login.defs
/etc/passwd
Exercise4 What is umask ?
What is file attributes?
What is sudoedit ?
symbol
• > Creates a new file containing standard output. If the specified file exists, it’s overwritten.
• >> Appends standard output to the existing file. If the specified file doesn’t exist, it’s created.
• 2> Creates a new file containing standard error. If the specified file exists, it’s overwritten.
• 2>> Appends standard error to the existing file. If the specified file doesn’t exist, it’s created.
• &> Creates a new file containing both standard output and standard error. If the specified file exists, it’s overwritten.
• < Sends the contents of the specified file to be used as standard input. • << Accepts text on the following lines as standard input. • <> Causes the specified file to be used for both standard input and
standard output.
Linux installation & package management
Install: some time you should install packages(program) for example MySQL packages. Type of packages are URL, .rpm, name, … . yum install package1 [package2] …
Upgrade: some time you should upgrade program for example change MySQL 4 to 5. yum upgrade [package1] [package2]
Update: some time you should update program for example MySQL 5 to 5.1. yum update [package1] [package2] …
Uninstall: some time you should uninstall program for example erase MySQL. remove | erase [package1] [package2] ….
Linux installation & package management(cont’d)
Another command for package management:
rpm just manage .rpm packages
rpm –i -> install
rpm –U -> upgrade
rpm –v -> print verbose information
rpm –h -> print 50 hash marks as the package archive is unpacked. Use with –v
rpm –e -> erase or uninstall
rpm –Uvh package.rpm
Linux installation & package management(cont’d)
Another command for package management:
wget: download from network and support http, https and ftp.
wget –c -> continue
wget –d ->debug
For install all packages you need make file that and compile and copy configure. For example ./configure -> make -> make install
Linux installation & package management(cont’d)
Important file:
/etc/yum
/etc/yum.conf
/etc/yum.repos.d
Exercise5
install mc packages from local use yum
go to /usr/share/doc and find mc files
Work by mc command
Configure disk partitions
sda1 sda2
LVM
Sda(n)
active Primary[4] Extended[5->]
LVM(Logical Volume Manager) partition
Standard partition
Extended : same as primary but don’t have file system and create logical partition on it and their have fs
Configure disk partitions(cont’d)
Configure disk partitions(cont’d)
A partition can be primary, extended and active Just 1 active, 4 primary Name of hard: sda or hda Name of partition: sda1, sda2, … . Name of device: cdrw, cdrom, sdb, … . fdisk: partition table in linux
fdisk –l : list of all partition->fdisk –l name: details for name
fdisk [name of disk] -> fdisk /dev/sda : manage sda Interactive area m for help
Configure disk partitions(cont’d)
a : bootable flag
n : new partition
q : exit with out save
w : write and exit
d : delete a partition
parted : same as fdisk
partx : show number of partition for sda
Configure disk partitions(cont’d)
Create file system on partition
mke2fs : create ext2,ext3,ext4 fs
resize2fs : resize ext2,ext3,ext4 fs
mkfs: build a linux fs
mkswap : set up a linux swap area
Configure disk partitions(cont’d)
Logical Volume Manager, or LVM, is a storage management solution that allows administrators to divide hard drive space into physical volumes (PV), which can then be combined into logical volume groups (VG), which are then divided into logical volumes (LV) on which the file system and mount point are created.
Configure disk partitions(cont’d)
Configure disk partitions(cont’d)
Example: lvm>
pvcreate pv1
vgcreate vg1
lvcraete –L 10g -n lv1 vg1
Mkfs.ext4 /dev/vg1/lv1
Important files:
/dev/*
/sbin/vg*
/etc/fstab
Exercise6
Create lvm disk and vg and pv
Create ext4 file system on lvm
Manage disk quota & create quota report
File system base disk quota allocation User or group based disk quota allocation
Hard limit – For example, if you specify 2GB as hard limit, user will not be able to create new files after 2GB
Soft limit – For example, if you specify 1GB as soft limit, user will get a warning message “disk quota exceeded”, once they reach 1GB limit. But, they’ll still be able to create new files until they reach the hard limit
Grace Period – For example, if you specify 10 days as a grace period, after user reach their hard limit, they would be allowed additional 10 days to create new files. In that time period, they should try to get back to the quota limit.
Manage disk quota & create quota report(cont’d)
Create user and group for disk quota
Enable disk quota check : ->go fstab
LABEL=/home /home ext2 defaults,usrquota,grpquota 1 2
mount -n -o remount /
Reboot server
Show disk quota: quotacheck –avug
a: Check all quota-enabled file system
v: Verbose mode
u: Check for user disk quota
g: Check for group disk quota
Assigned disk quota: edquota username
Manage disk quota & create quota report(cont’d)
Report disk quota:
Repquota /home
Add quota check daily:
Create cron -> next session
Example: go fastab
/dev/VolGroup1/LogVol1 /home ext3 defaults,usrquota 1 2
Symbolic links, FHS
Link : connection between 2 files. For example /var/spool/mail -> /var/mail
Soft link (symbolic link) : point to file
Hard link : pointer of file in directory so if delete file link is exist
ln : make links between files ln –s : create soft link
ln –p : hard link to soft link
FHS(Filesystem Hierarchy System)
Writing shell script
What is shell script : Shell scripts are plain-text files, so you create them in text editors. A shell script begins with a line that identifies the shell that’s used to run it.
The execute text file begin with #!/bin and if you want use bash commands you insert #!/bin/bash ->sharp bang
For execute that you should set execute permission and enter ./filename.
Writing shell script(cont’d)
Writing shell script(cont’d)
Commands for shell script: set: for see system variables
BASH= Our shell name BASH_VERSION= Our shell version name COLUMNS= No. of columns for our screen HOME= Our home directory LINES= No. of columns for our screen LOGNAME= Our logging name OSTYPE= Our OS type PATH= Our path settings PS1= Our prompt settings PWD= Our current working directory SHELL= Our shell name USERNAME= User name who is currently login to this PC
Writing shell script(cont’d)
export: definition variable -> export var=10 echo: show quantity of variable -> echo $var
-n Do not output the trailing new line. -e Enable interpretation of the following backslash escaped
characters in the strings: \a alert (bell) \b backspace \c suppress trailing new line \n new line \r carriage return \t horizontal tab \\ backslash
if [ -n "$var" ]; then echo "not empty"
else echo "empty"
Writing shell script(cont’d)
How to use and create function:
What is function?
Example: function today {
echo “today is”
date +”%A,%B,%D,%Y”
}
Run today
type: show type of command
Writing shell script(cont’d)
Conditions and loops: what is condition and loop? if: what is .bashrc->directory of store information of user bash and
variable and etc. if [ condition]; then commands elif commands else commands fi while: for like while while [condition ]
do commands done
Writing shell script(cont’d)
• Example: #!/bin/bash x=“welcome” y=“welcome to linux” z=15 if [ $z –gt 10]; then echo “z=“$z; else if [ $x –eq $y ]; then echo “x=y”; fi echo “var=\n” $x ”\n” $y “\n” $z fi
Writing shell script(cont’d)
for: for { variable name } in { list } Condition:
Exercise7 Input 2 number and compare their. so calculate a*b,
a+b, a/b, a10.
Working with archive files
tar: extract, archive, … .
tar –cvf filename.tar filetoarchive
tar –xzf filename –C directory->extract & zip
gzip: compress a file -> gunzip: expand a file
zip & unzip: similar to gzip
System resource management
Run level: 0 – 6 -> /etc/grub.conf
0: turn on
6: turn off
pstree: Shows the Parent-Child Relation Between Processes
gstack: print a stack trace of a running process -> gstack [PID]
more /proc/cpuinfo
top: display Linux task
s -> change delay
z -> change color
h -> help
b -> bold
q -> exit
System resource management(cont’d)
ps: report a snapshot of current process -> ps aux USER: The name of the user who started the process.
PID: The PID of the process. The command ps aux sorts the processes by their PID.
%CPU: The percentage of CPU time the process has used since startup.
%MEM: The percentage of memory the process is currently using.
VSZ: The virtual memory size, which is the total amount of memory claimed by this process.
RSS: The resident memory size, which is the amount of memory the process currently has in use.
TTY: The terminal (TTY) from which the process was started. A question mark indicates a daemon process that is not associated to any TTY.
System resource management(cont’d)
STAT: The current status of the process.
START: The time at which the process was started.
TIME: The total amount of system time this process has been using since it started.
COMMAND: The command that was used to start this process. If the name of this command is between square brackets (you can see quite a few examples of this in (Listing 9-5), the process is not started with a command at the command line, but is a kernel thread.
System resource management(cont’d)
Use limited system resource use ulimit command: Core File Limits The -c option limits the size of core dumps, which are
fi les created for
debugging purposes in certain types of program crashes.
File Limits The -f option limits the size of fi les that may be created by the shell, and –n limits the number of open fi le descriptors. (Most systems don’t honor the -n limits, though.)
Process Limits The -u option limits the number of processes a user may run, and -t limits the total CPU time in seconds.
Memory Limits The -v option sets the total amount of virtual memory available to the shell, -s sets the maximum stack size, -m sets the maximum resident set size, -d limits programs’ data set size, and -l sets the maximum size that may be locked into memory.
System resource management(cont’d)
Hard and Soft Limits The -H and -S options modify other options, causing them to be set as hard or soft limits, respectively. Hard limits may not be subsequently increased, but soft limits may be. If neither option is provided, ulimit sets both the hard and soft limits for the feature specified.
Current Settings Passing -a causes ulimit to report its current settings.
Important directories: /proc/*
/boot/System.map –
Exercise8 Read command : pgrep, pkill, free, kill,
Working with debuggers in Linux
After you write shell script you need debug it and some time you need debug software for this problem we use gdb command.
gdb: GNU debugger
In shell script use (gdb) commands……(gdb)
For software use gdb (option) [ pid or name of software]
Some option of gdb
Working with debuggers in Linux(cont’d)
h: for help q: quit run: run [program name] bt: print call stack = where
up: move up one stack frame down: != up frame: frame n ->go to frame n info: info frame ->information current frame
Exercise9 If you need Debugger command see Debugging with gdb
Tenth Edition, for gdb version 7.6.1.2013, Richard Stallman, Roland Pesch, Stan Shebs, 658paper
gpg command
Checksum: when we transfer or storage data between computers maybe information destroyed and we don’t understand or understand not solve their so we use a method to solve it problem. For example CRC checksum. You Consider, checksum different with encrypt. In data encryption goal is encrypt and in checksum goal is solve and understand mistake. For best data transfer we encrypt and checksum methods.
gpg command(cont’d)
MD5: is a hashing method. First get checksum of data then get hash their.
gpg command(cont’d)
Encryption (gpg GNU Privacy Guard) : 2 way for encryption signature file: just who make file can access it
gpg --output file.sig --detach-sign file
Primary and public key: just who Possessing primary key can access it and other just encrypt file with public key. gpg --gen-key->generate private and public key
gpg --list-key->list of key
gpg --edit-key keyID->edit key
gpg --output [fileforsendkey.gpg] --export->create export key
gpg --armor --output [fileforsendkey.gpg] --export-> Creates ASCII armored output
Security in linux
Physical Access Problems Set bios password
Set grub password
[grub-crypt --sha-256] or [grub-crypt --md5]
Copy to /etc/grub.conf -> password –md5 ………………….
Stolen Passwords
Local Program Bugs Set SUID and SGID bit for program
find / -perm +6000 -type f
Server Bugs
Denial-of-Service Attacks
Encryption Issues
Security in linux(cont’d)
Creating Firewall Rules: iptable
/etc/services: see the services run on linux and more details about them.
netstat -> netstat –ap : see active internet connection
Security in linux(cont’d)
Security in linux(cont’d)
The iptables program is the utility that manages firewall.
First you should know about packet and packet filtering.
iptables -L -t filter Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination
Security in linux(cont’d)
Security in linux(cont’d)
#!/bin/bash iptables -F INPUT iptables -F FORWARD iptables -F OUTPUT iptables -P INPUT DROP iptables -P FORWARD DROP iptables -P OUTPUT DROP # Let traffic on the loopback interface pass iptables -A OUTPUT -d 127.0.0.1 -o lo -j ACCEPT iptables -A INPUT -s 127.0.0.1 -i lo -j ACCEPT # Let DNS traffic pass iptables -A OUTPUT -p udp --dport 53 -j ACCEPT iptables -A INPUT -p udp --sport 53 -j ACCEPT
# Let clients' TCP traffic pass iptables -A OUTPUT -p tcp --sport 1024:65535 -m state \ --state NEW,ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -p tcp --dport 1024:65535 -m state \ --state ESTABLISHED,RELATED -j ACCEPT # Let local connections to local SSH server pass iptables -A OUTPUT -p tcp --sport 22 -d 172.24.1.0/24 -m state \ --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -p tcp --dport 22 -s 172.24.1.0/24 -m state \ --state NEW,ESTABLISHED,RELATED -j ACCEPT
Do automate tasks in Linux, cron job
What is automate task ?
When use automate task? Some system maintenance tasks should be
performed at regular intervals and are highly automated
Automate task in linux? at
cron: cron is a daemon
at & cron: at just run once and cron run ongoing
Command for cron job:
Do automate tasks in Linux, cron job
crontab: execute program to configuration cron crontab –l : see cron job crontab [-u user] [-l | -e | -r] [file]
/etc/cron.d: configuration directory -> sysstat /var/spool/cron: cron job Create cron job:
02 4 * * * root run-parts /etc/cron.daily This line begins with five fields that specify the time. The fields
are, in order, the minute (0–59), the hour (0–23), the day of the month (1–31), the month
(1–12), and the day of the week (0–7; both 0 and 7 correspond to Sunday)
Do automate tasks in Linux, cron job
In all cases, you can specify multiple values in several ways: An asterisk (*) matches all possible values.
A list separated by commas (such as 0,6,12,18) matches any of the specified values.
Two values separated by a dash (-) indicate a range, inclusive of the end points. For instance, 9-17 in the hour field specifies a time of from 9:00 a.m. to 5:00 p.m.
A slash, when used in conjunction with some other multi value option, specifies stepped values /a range in which some members are skipped. For instance, */10 in the minute field indicates a job that’s run every 10 minutes
at: at -f commands.txt noon
Working with tcpdump
Capture packets from a particular Ethernet interface using tcpdump -i
Capture only N number of packets using tcpdump -c
Display Captured Packets in ASCII using tcpdump -A
Working with tcpdump
Display Captured Packets in HEX and ASCII using tcpdump -XX
Capture the packets and write into a file using tcpdump -w
Reading the packets from a saved file using tcpdump -r Capture packets with IP address using tcpdump -n Capture packets with proper readable timestamp
using tcpdump -tttt Read packets longer than N bytes
tcpdump -w g_1024.pcap greater 1024
Receive only the packets of a specific protocol type tcpdump -i eth0 arp
Working with tcpdump
Receive packets flows on a particular port using tcpdump port tcpdump -i eth0 port 22
Capture packets for particular destination IP and Port tcpdump -w comm.pcap -i eth0 dst 16.181.170.246
and port 22
tcpdump Filter Packets – Capture all the packets other than arp and rarp tcpdump -i eth0 not arp and not rarp
Introduction to network
tcp/ip and osi model: physical layer data link layer network layer transport layer session layer presentation layer application layer
Topology of network Ring Star bus
protocol
Introduction to network (cont’d)
IP DNS DHCP Port telnet and ssh ftp http and https Arp and rarp icmp
Network configuration
Ifconfig
Setup
DNS Forward
Primary
Secondary
Stub
Reverse
/etc/resolv.conf
/etc/hosts
Network configuration(cont’d)
DHCP How to work dhcp ? /etc/dhcp/dhcpd.conf
Telnet & SSH how to work telnet or ssh? ssh 192.168.1.100 telnet 192.168.1.100
Network configuration(cont’d)
icmp
Ping
tracepath
ftp
How to work ftp?
scp