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Mitesh Shah

Linux Expert | Automation Enthusiast | Security Consultant

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Network Clients

18 minutes to read (1862 words) ()

Overview

Web Clients

  • Links is a Text Based (Non GUI) Web Broser.
  • Provided by the elinks package.
  • Full support for Frames and SSL.

Examples:

[mitesh@Matrix ~]$ links http://www.redhat.com
[mitesh@Matrix ~]$ links -dump http://www.redhat.com
[mitesh@Matrix ~]$ links -source http://www.redhat.com

Wget

  • The wget is a non-interactive network downloader.
  • Retrieves files via HTTP and FTP.

Options:

/-----------------------------------------------------------------------------------------------\
|												|
|	--continue (-c)	|	Continue Partially Downloaded File				|
|												|
|	--tries=number	|	Retry the specified number of times to download the files	|
|	--wait=seconds	|	Wait the specified number of seconds between the retrievals	|
|												|
|	--recursive	|	Turn on recursive retrieving					|
|	--level=depth	|	Specify recursion maximum depth level				|
|			|	(The default maximum depth is 5)				|
|	--convert-links	|	After download is complete convert all links,			|
|			|	To make them suitable for local viewing				|
|												|
\-----------------------------------------------------------------------------------------------/

Examples:

[mitesh@Matrix ~]$ wget http://www.redhat.com/training/index.html

[mitesh@Matrix ~]$ wget -c ftp://ftp.site.com/selinux.tar.gz

[mitesh@Matrix ~]$ wget --tries=50 --wait=30 ftp://ftp.site.com/files

[mitesh@Matrix ~]$ wget --recursive --level=1 --convert-links http://www.site.com

Google Chrome/Firefox

  • Tabbed Browsing
  • Popup Blocking
  • Cookie Manageent
  • Themes and Extensions
  • Multi-Engine Search Bar
  • Supports For Many Popular Plug-ins

Email and Messaging

Graphical Mail Clients

Evolution
  • Flexible Email & Groupware Tool
  • Used For
    • Email Access
    • Maintain a Calendar, Tasklist and Contacts Database
Thunderbird
  • Standalone Mozilla Email Client
  • Used For
    • Email Access
    • Usenet and RSS Supports

Security and Anti-spam Features:

  • Evolution and Thunderbird both support the Bayesian Spam Fileters.

  • Evolution and Thunderbird both allows emails to be signed and encrypted.
  • Evolution integrates supports for the GPG (GNU Privacy Guard) utility for this purpose.
  • By Default, Thunderbird uses S/MIME for this purpose but use GPG with the help of the plugin called EnigMail.

Non-GUI Mail Clients

Mutt
  • Mappable Hotkeys
  • Highly Configurable
  • Context Sensitive Help with ?
  • Message Threading & Colorizing
  • GNU Privacy Guard (GPG) Integration
  • Supports POP, IMAP and LocalMailboxes

Examples:

  • You Can Read One Mailbox (POP Account, IMAP Account or Local Mailbox) At A Time.
# Start The Local Mailbox
[mitesh@Matrix ~]$ mutt

# The mutt -f Starts The Specified Mailbox
[mitesh@Matrix ~]$ mutt -f imaps://user@server

Note!: You Can Change Which Mailbox Mutt Viewed By Default, By Altering Its Configuration File ~/.muttrc.


Open SSH - Secure Remote Shell

  • SSH Allows Remote Logins & Remote Command Execution Via A Secure Encrypted Connections.

Syntax:

ssh [user@]hostname
ssh [user@]hostname command

Examples:

[mitesh@Matrix ~]$ ssh localhost
[mitesh@Matrix ~]$ ssh root@bluehost.com

[mitesh@Matrix ~]$ ssh neo@localhost 'df -h'
neo@localhost's password:

Filesystem            		Size  Used Avail Use% Mounted on
/dev/mapper/vg_Matrix-lv_root	 50G  2.4G   45G   6% /
tmpfs                 		495M  472K  494M   1% /dev/shm
/dev/sda1             		485M   30M  430M   7% /boot
/dev/mapper/vg_Matrix-lv_home	 59G  3.2G   53G   6% /home

scp - Secure File Transfer

  • The scp works like cp command.
  • The scp is a secure remote file copy program.

Syntax:

scp [OPTIONS] [[user@]host1:]file1... [[user@]host2:]file2

* Options:
-r(recursive):          Recursively copy an entire directory tree
-p(preserve):           Preserve the permissions, ownership, and time stamps

Examples:

# Download the process.log file
[mitesh@Matrix ~]$ scp neo@localhost:process.log .
neo@localhost's password:
process.log                                        100% 8843     8.6KB/s   00:00

# Upload the userstat.log file
[mitesh@Matrix ~]$ scp userstat.log neo@localhost:.
neo@localhost\'s password:
userstat.log                                        100% 8843     8.6KB/s   00:00

rsync - Efficient File Sync

  • The rsync is a faster than scp.
  • The rsync copies the difference in like files.
  • The rsync uses a secure ssh connections for transport the files.
  • The rsync is a fast, versatile, remote (and local) file-copying tool.

Examples:

[mitesh@Matrix ~]$ rsync --progress neo@localhost:file1 .
neo@localhost's password:
file1
55 100%   53.71kB/s    0:00:00 (xfer#1, to-check=0/1)

sent 36 bytes  received 129 bytes  36.67 bytes/sec
total size is 55  speedup is 0.33

[mitesh@Matrix ~]$ cat file1
Hello Linux!
Welcome to the OSS!

Open SSH Keybased Authentication

  • SSH Allows You To Authenticate Using The Private-Public Key Schema.
  • Optional, Password less, But Still Secure Authentication

Uses Two Keys Generated By The ssh-keygen

  1. Private Key
    • Private Key Stay On Your System
    • Usually Passphrase Protected (Recommended)
  2. Public Key
    • Public Key Is Copied To The Destination With ssh-copy-id
    • By Default ssh-copy-id copy the ~/.ssh/id_rsa.pub

Syntax:

ssh-copy-id [user@]hostname

Examples:

ssh-copy-id -i ~/.ssh/identity.pub [user@]hostname
ssh-copy-id -i ~/.ssh/id_rsa.pub [user@]hostname
ssh-copy-id -i ~/.ssh/id_dsa.pub [user@]hostname

NOTE!: Older system may not have ssh-copy-id command
Which will require you to manually copy your public keys to the destination system,
And append it to the ~/.ssh/authorized_keys file, or create the file if it does not exist.
The ~/.ssh/authorized_keys file must be readable by you. Otherwise ssh will ignore it.


Structure Of ssh-keygen

/---------------------------------------------------------------\
|								|
|				identity	Private	600	|
|			RSA1					|
|				identity.pub	Public	644	|
|								|
|	ssh-keygen						|
|								|
|				id_rsa		Private	600	|
|			RSA					|
|				id_rsa.pub	Public	644	|
|								|
|				id_dsa		Private	600	|
|			DSA					|
|				id_dsa.pub	Public	644	|
|								|
\---------------------------------------------------------------/

Examples:

# Generate Protocol2 RSA Key Pairs
[mitesh@Matrix ~]$ ssh-keygen

# Generate Protocol2 DSA Key Pairs
[mitesh@Matrix ~]$ ssh-keygen -t dsa

# Generate Protocol1 Key Pairs
[mitesh@Matrix ~]$ ssh-keygen -t rsa1

NOTE!: By Default ssh-keygen Generates Protocol2 RSA Key Pairs.


ssh-agent

  • If you created your private key with a passphrase, which is highly recommended for the security reasons, Then whenever the key is used to connect to the other machines, you must type your passphrase.

  • An Authentication Agent Stores The Decrypted Private Keys
  • Thus, Passphrase only need to be entered once.
  • In GNOME Authentication Agent is provided automatically.
  • Otherwise, You will need to create a Agent-Managed Shell with ssh-agent command
[mitesh@Matrix ~]$ ssh-agent bash
[mitesh@Matrix ~]$
  • The Keys are added to the Agent with ssh-add command
  • If no filename is specified, The Keys stored in ~/.ssh/id_rsa and ~/.ssh/id_dsa will be used
  • You can view the list of stored keys by running
[mitesh@Matrix ~]$ ssh-add -l

NOTE!: When you are finished, Just type exit to return your original shell.
When the Agent is terminated, All your keys are forgotten.


FTP Clients

  • Several FTP Clients are availables such as sftp, lftp, lftpget, gftp and many more.

sftp

  • Interactive Secure File Transfer Program.
  • The sftp uses a secure ssh connections for transport the files.

lftp:

  • More Featureful File Transfer Program.

Examples:

[mitesh@Matrix ~]$ lftp ftp.example.com
[mitesh@Matrix ~]$ lftp -u joe ftp.example.com

lftpget

  • Non-interactive File Transfer Program.

Examples:

[mitesh@Matrix ~]$ lftpget ftp://ftp.example.com/pub/file.txt

gftp

  • Graphical File Transfer Program.
  • Applications -> Internet -> gFTP
  • Allows Drag and Drop Transfer
  • Anonymous or Authenticated Access
  • Optional Secure Transfer vis SSH (sftp)

SMB Clients

  • FTP Like Client To Access SMB/CIFS Resources On Server
  • SMB Clients are used to access the shared resources on the MS Windows Network

Options:

-W:	Workgroup or Domain
-U:	Username
-N:	Suppress password prompt (Useful when accessing a service that does not require a password)

File Transfer with Nautilus

  • Nautilus are also used to access the remote file shares.
  • Places -> Connect to Server
  • Allows Drag and Drop File Transfer
  • Graphically Browse With Multiple Protocols
  • Suported Connection Types:
  • SSH
  • FTP
  • SFTP
  • WebDAV (HTTP)
  • Secure WebDAV (HTTPS)
  • Microsoft Windows Shares

Nautilus URL

ftp://ftp.example.com		|	Connects via ftp to ftp.example.com
sftp://user@ftp.example.com	|	Same as above, but connecting securely via ssh as user

smb://				|	List all available SMB Servers
smb://example			|	List SMB Share on example server
smb://user@example		|	Same as above but authenticate as user

Xorg Clients

  • One Of The Most Important Features Of Xorg Is Its Client/Server Architecture, That Makes Any Graphical Application On Linux System Completely Network Transparent.

  • That Means You Can Start Any Graphical Application On The Remote System & That Application Displayed On The Local System.
  • The Graphical Application Running In This Way
  • Affects Files On The Remote System
  • Take Up Resources (Cpu Cycles, Memory, Etc) On The Remote System
  • And That Graphical Application Only Displayed On The Local System

Note!: All Graphical Applications Are X Clients & Connects To The Remote X Server Via TCP/IP
By Default, The Data Transfer Is Not Encrypted But Can Be Tunneled Securely Over An SSH Connection

ssh -X [user@]hostname xterm &

Network Diagnostic Tools

ping

  • Detects If It Is Possible To Communicate With Other Systems.
  • Many System No Longer Respond To The Pings.

host

  • DNS Lookup Utility.
  • It is normally used to convert Hostnames to IP addresses and vice versa.

dig

  • DNS Lookup Utility.
  • Similar to host but greater in details.

netstat

  • Provides a Number Of Network Statistics.

traceroute

  • Display The List Of Computers(IP Addresses) Through Which The Packet Is Passed To Reach Their Destination.




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