SSH Passwordless Login Using SSH Keygen in 5 Easy Steps

SSH (Secure SHELL) is an open source and most trusted network protocol that is used to login into remote servers for execution of commands and programs. It is also used to transfer files from one computer to another computer over the network using secure copy (SCP) Protocol.

In this article we will show you how to setup password-less login on RHEL/CentOS 7.x/6.x/5.x and Fedora usingssh keys to connect to remote Linux servers without entering password. Using Password-less login with SSH keys will increase the trust between two Linux servers for easy file synchronization or transfer.

My Setup Environment

SSH Client : 192.168.0.12 ( Fedora 21 )
SSH Remote Host : 192.168.0.11 ( CentOS 7 )

If you are dealing with number of Linux remote servers, then SSH Password-less login is one of the best way to automate tasks such as automatic backups with scripts, synchronization files using scp and remote command execution.

In this example we will setup SSH password-less automatic login from server 192.168.0.12 as user tecmint to192.168.0.11 with user sheena.

Step 1: Create Authentication SSH-Kegen Keys on – (192.168.0.12)

First login into server 192.168.0.12 with user tecmint and generate a pair of public keys using following command.

[tecmint@tecmint.com ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/tecmint/.ssh/id_rsa): [Press enter key]
Created directory '/home/tecmint/.ssh'.
Enter passphrase (empty for no passphrase): [Press enter key]
Enter same passphrase again: [Press enter key]
Your identification has been saved in /home/tecmint/.ssh/id_rsa.
Your public key has been saved in /home/tecmint/.ssh/id_rsa.pub.
The key fingerprint is:
5f:ad:40:00:8a:d1:9b:99:b3:b0:f8:08:99:c3:ed:d3 tecmint@tecmint.com
The key's randomart image is:
+--[ RSA 2048]----+
|        ..oooE.++|
|         o. o.o  |
|          ..   . |
|         o  . . o|
|        S .  . + |
|       . .    . o|
|      . o o    ..|
|       + +       |
|        +.       |
+-----------------+

Step 2: Create .ssh Directory on – 192.168.0.11

Use SSH from server 192.168.0.12 to connect server 192.168.0.11 using sheena as user and create .sshdirectory under it, using following command.

[tecmint@tecmint ~]$ ssh sheena@192.168.0.11 mkdir -p .ssh
The authenticity of host '192.168.0.11 (192.168.0.11)' can't be established.
RSA key fingerprint is 45:0e:28:11:d6:81:62:16:04:3f:db:38:02:la:22:4e.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.0.11' (ECDSA) to the list of known hosts.
sheena@192.168.0.11's password: [Enter Your Password Here]

Step 3: Upload Generated Public Keys to – 192.168.0.11

Use SSH from server 192.168.0.12 and upload new generated public key (id_rsa.pub) on server 192.168.0.11under sheena‘s .ssh directory as a file name authorized_keys.

[tecmint@tecmint ~]$ cat .ssh/id_rsa.pub | ssh sheena@192.168.0.11 'cat >> .ssh/authorized_keys'
sheena@192.168.1.2's password: [Enter Your Password Here]

Step 4: Set Permissions on – 192.168.0.11

Due to different SSH versions on servers, we need to set permissions on .ssh directory and authorized_keys file.

[tecmint@tecmint ~]$ ssh sheena@192.168.0.11 "chmod 700 .ssh; chmod 640 .ssh/authorized_keys"
sheena@192.168.0.11's password: [Enter Your Password Here]

Step 5: Login from 192.168.0.12 to 192.168.0.11 Server without Password

From now onwards you can log into 192.168.0.11 as sheena user from server 192.168.0.12 as tecmint user without password.

[tecmint@tecmint ~]$ ssh sheena@192.168.0.11

Copying files & directories to remote servers

15 scp commands securely copy files to remote servers Linux

Basically to copy files/directories from one Server/Machine to another we have to use file sharing services such as Samba(SMB) OR NFS, but we don’t want to create an Samba server / NFS server just to copy required files/directories one time. Here is an solution where we can make use of 15 scp commands securely copy files to remote server. This SCP commands works an all the Unix / Linux flavors.

scp copies files between hosts on a network. It uses SSH for data transfer, and uses the same authentication and provides the same security as SSH. Unlike rcp, scp will ask for passwords or passphrases if they are needed for authentication.

SCP command syntax

scp [options] Source Destination

15 scp commands advantages

• scp use SSH as dependant 
• SCP use cipher systems AES, Blowfish, 3DES, CAST128, and Arcfour which are supported by SSH
• We can also use passphrase to authenticate

Environment for demonstration

• Server (Source) 192.168.4.20
• Desktop (Destination) 192.168.4.200

1. Copy File from Source to Destination ( Server1 –> Server2)

A simple way to copy the file from server to desktop use below command.

[root@TechTutorials ~]# scp test root@192.168.4.200:/root/Desktop
The authenticity of host '192.168.4.200 (192.168.4.200)' can't be established.
ECDSA key fingerprint is da:58:0e:40:bc:6b:4c:d2:d1:fc:3f:c6:4f:64:93:2e.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.4.200' (ECDSA) to the list of known hosts.
root@192.168.4.200's password:
test.rpm 100% 14KB 14.2KB/s 00:00

2. Copy multiple files from source to destination

In this below example we just copy multiple files to remote host, as custom selected files (required files)

[root@TechTutorials ~]# scp initial-setup-ks.cfg file1 file2 root@192.168.4.200:/root/Desktop/

scp commands

3. Copy directory instead of copying single / multiple files

If we have an multiple files in a directory instead of copying all the files separately we can just copy entire directory as it is to destination. Let’s see an example command

[root@TechTutorials ~]# scp -r test root@192.168.4.200:/tmp/
root@192.168.4.200's password:
ABD 100% 0 0.0KB/s 00:00
uyyo1 100% 0 0.0KB/s 00:00
123ks 100% 0 0.0KB/s 00:00
yupsd45 100% 0 0.0KB/s 00:00
56767 100% 0 0.0KB/s 00:00
UYSISDNF 100% 0 0.0KB/s 00:00
hyie 100% 0 0.0KB/s 00:00
ABD 100% 0 0.0KB/s 00:00
UYSISDNF 100% 0 0.0KB/s 00:00

 As we see an above example we copied an ‘test’ directory to destination server. To copy directory ‘-r’ option have to use along with scp command

4. Preserving the time stamp as like source

When you copy files / directories from Source to Destination, we get an latest time stamp in destination side. Copy the files / directories exact as like source (all attributes will be copied) so exact time stamp and permissions will be copied.

[root@TechTutorials ~]# scp -rvp test root@192.168.4.200:/root/Desktop/

preserving attributes

5. Compress and copy files / directories faster – 15 scp commands

Using ‘-C’ option will compress and copy the files / directories to destination. Data compression will happens in Network level and destination receives data size as it is in source.

[root@TechTutorials ~]# scp -C linux-nrpe-agent.tar.gz root@192.168.4.200:/root/
root@192.168.4.200's password:
linux-nrpe-agent.tar.gz 100% 6840KB 6.7MB/s 00:00

6. Know your copy status

If you would like to see an copy status, we have to use ‘-v’ option along with scp command. Verbose will be displayed 

[root@TechTutorials ~]# scp -v file1 root@192.168.4.200:/root/
Executing: program /usr/bin/ssh host 192.168.4.200, user root, command scp -v -t /root/
OpenSSH_6.6.1, OpenSSL 1.0.1e-fips 11 Feb 2013
root@192.168.4.200's password:
debug1: Authentication succeeded (password).
Authenticated to 192.168.4.200 ([192.168.4.200]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
debug1: Sending command: scp -v -t /root/
Sending file modes: C0644 32 file1
Sink: C0644 32 file1
file1 100% 32 0.0KB/s 00:00
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: channel 0: free: client-session, nchannels 1
debug1: fd 0 clearing O_NONBLOCK
debug1: fd 1 clearing O_NONBLOCK
Transferred: sent 2624, received 2308 bytes, in 0.1 seconds
Bytes per second: sent 19033.1, received 16741.0
debug1: Exit status 0

7. Use random port to along with scp command

We can also specify particular port to copy data from source to destination

[root@TechTutorials ~]# scp -P 22 file2 root@192.168.4.200:/root/Desktop/
root@192.168.4.200's password:
file2 100% 32 0.0KB/s 00:00

8. Suppress scp command output (verbose) warning and error messages Just copy

Quiet mode: disables the progress meter as well as warning and diagnostic messages from ssh

[root@TechTutorials ~]# scp -vq file1 root@192.168.4.200:/tmp/
Executing: program /usr/bin/ssh host 192.168.4.200, user root, command scp -v -t /tmp/
root@192.168.4.200's password:
Sending file modes: C0644 32 file1
Sink: C0644 32 file1

9. copy/scp  files/directories without using password

Generate an ssh key and copy to destination which makes passwordless connection

[root@TechTutorials ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
ff:37:20:a2:52:a3:88:f8:23:de:ef:ef:79:ed:a8:49 root@TechTutorials
The key's randomart image is:
+--[ RSA 2048]----+
| |
| |
| |
| |
| S |
| o ... . |
|.. . o E .o. . |
|+ + o o o..o o |
|.+.oo+o*o..... . |
+-----------------+
[root@TechTutorials ~]# ssh-copy-id root@192.168.4.200
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.4.200's password:
Number of key(s) added: 1
Now try logging into the machine, with: "ssh 'root@192.168.4.200'"
and check to make sure that only the key(s) you wanted were added.

Now initiate an scp will not ask any password

[root@TechTutorials ~]# scp key stdin root@192.168.4.200:/root/

without password copy files

10. Instead of password use key file

To use key file we have to mention ‘-i’ option along with 15 scp commands

[root@TechTutorials ~]# scp -i privatekey.key anaconda-ks.cfg root@192.168.4.200:/root/

11. Use SSH config file to scp

Here in 15 scp commands we can also use predefined  parameters to make scp copy easier

All possible values with scp command

 AddressFamily
BatchMode
BindAddress
CanonicalDomains
CanonicalizeFallbackLocal
CanonicalizeHostname
CanonicalizeMaxDots
CanonicalizePermittedCNAMEs
ChallengeResponseAuthentication
CheckHostIP
Cipher
Ciphers
Compression
CompressionLevel
ConnectionAttempts
ConnectTimeout
ControlMaster
ControlPath
ControlPersist
GlobalKnownHostsFile
GSSAPIAuthentication
GSSAPIDelegateCredentials
HashKnownHosts
Host
HostbasedAuthentication
HostKeyAlgorithms
HostKeyAlias
HostName
IdentityFile
IdentitiesOnly
IPQoS
KbdInteractiveAuthentication
KbdInteractiveDevices
KexAlgorithms
LogLevel
MACs
NoHostAuthenticationForLocalhost
NumberOfPasswordPrompts
PasswordAuthentication
PKCS11Provider
Port
PreferredAuthentications
Protocol
ProxyCommand
PubkeyAuthentication
RekeyLimit
RhostsRSAAuthentication
RSAAuthentication
SendEnv
ServerAliveInterval
ServerAliveCountMax
StrictHostKeyChecking
TCPKeepAlive
UsePrivilegedPort
User
UserKnownHostsFile
VerifyHostKeyDNS

[root@TechTutorials ~]# scp -F .ssh/config anaconda-ks.cfg root@192.168.4.200:/root/

12. Execute remote to remote host copy

Scenario is copy files from Server2 –> Server3 execute scp command from Server1

[root@TechTutorials ~]# scp root@192.168.2.20:/root/file1 root@192.168.4.200:/tmp/

13. Use different Encryption algorithm to copy

As i mentioned in above of this article SSH will support not only AES encryption it will also support more algorithms, we can also specify which algorithm yo want to use 

[root@TechTutorials ~]# scp -c 3des nagios-plugins-2.1.1.tar.gz root@192.168.4.200:/tmp/
nagios-plugins-2.1.1.tar.gz 100% 2615KB 2.6MB/s 00:00

14. Use specified bandwidth

Whereas we may not have much bandwidth to copy files from source to destination, if we push numbers of files yet time with low bandwidth Network will choke/breaks. Instead of breaking we take an action to limit and copy. All the values of bandwidth we mention in Kilo-bits.

[root@TechTutorials ~]# scp -l 500 nagios-plugins-2.1.1.tar.gz root@192.168.4.200:/tmp/
nagios-plugins-2.1.1.tar.gz 100% 2615KB 63.8KB/s 00:41

15. Shell script to copy files / directories to multiple Servers with single command

To make 15 scp commands simple i made an simple scripts which help you to copy files/directories to multiple servers using single command. Use passwordless connection which makes your work more easier

To use this script we have to write list of servers in /tmp/destfile.txt

# vi /tmp/destfile.txt
192.168.4.200
192.168.4.2
192.168.4.90
#chmod 777 /tmp/destfile.txt

Now Create a file anywhere where to keep script file. In this example i want to keep my script in /scripts/ directory

# vi /scripts/multiscp.sh
#!/bin/bash
## Author: Ankam Ravi Kumar
## Purpose: Copy files to multiple Server using single script
## Date: 21st July 2016
echo -e "Please Enter the file path which you want to copy:\c"
read file
for dest in `cat /tmp/destfile.txt`; do
  scp -rC $file ${dest}:/tmp/
done

How to execute this file

# chmod u+x /scripts/multiple.sh
# sh /scripts/mutiple.sh

Output of the script

[root@Techtutorials ~]# sh multiscp.sh
Please Enter the file path which you want to copy:/root/test
root@192.168.4.129's password:
test                                                                                                         100%  550     0.5KB/s   00:00

Conclusion

15 scp commands which makes our life easy to copy files/directories instantly to remote servers.

Thanks for the read please write your feedback on the same.

Compressing files & directories (tar and zip)

20 useful tar and zip commands

Introduction to File compression and archiving

20 useful tar and zip commands  It is useful to store a group of files in one file for easy backup, for transfer to another directory, or for transfer to another computer. It is also useful to compress large files; compressed files take up less disk space and download faster via the Internet.

It is important to understand the distinction between an archive file and a compressed file. An archive file is a collection of files and directories stored in one file. The archive file is not compressed — it uses the same amount of disk space as all the individual files and directories combined. A compressed file is a collection of files and directories that are stored in one file and stored in a way that uses less disk space than all the individual files and directories combined. If disk space is a concern, compress rarely-used files, or place all such files in a single archive file and compress it.

Note: tar file is not a compressed file, but compressed file is archived file

As we so many extensions to compress the files using tar command, as we take few examples in this article. All the extensions will work to compress the files and directories but there compression ratio is different compare to each other. Based extension compression ratio we can use different options.

1. gzip

2. bzip

3. zip

Syntax: tar <File Name.tar> <directory / file path>

1. Archiving files using tar command

Archiving is not an compression of files and directories it’s an kind of group all the files and directories together in single file, instead of multiple files. After creating an archive file, we can’t see size difference in between actual file system size and archive file.

Let’s see an example below

[root@TechTutorial tar]# du -h *.txt   <<-- Files Size before creating an archive
44K     d.txt
44K     g.txt
44K     kumar.txt
44K     ravi.txt
44K     tech.txt
44K     test1.txt
44K     test2.txt
44K     test3.txt
44K     test4.txt
[root@TechTutorial tar]# tar -cvf ravi.tar *.txt   << to Create an Archive file command
d.txt
g.txt
kumar.txt
ravi.txt
tech.txt
test1.txt
test2.txt
test3.txt
test4.txt
[root@TechTutorial tar]# du -h ravi.tar  << -- After Creating an archive file size
380K    ravi.tar

explanation of tar command options

-c Create an archive file

-v verbose (display all files status to archive)

-f specifying the files

2. Extracting an archive file

In order to extract the archive file we have to use -x option along with tar command

[root@TechTutorial tar]# tar -xvf ravi.tar
d.txt
g.txt
kumar.txt
ravi.txt
tech.txt
test1.txt
test2.txt
test3.txt
test4.txt

3. Updating an archive file with newly created files

There is a requirement that, we have to update an archive file by adding only newly created files.  Adding only newly created files to archive will save us the lot of time.

Let’s see an example as shown below, when we use -u option along with tar command it will update the tar file with newly created files

[root@TechTutorial tar]# touch Techtutorials.txt
[root@TechTutorial tar]# tar -uvf ravi.tar *.txt
Techtutorials.txt

4. List files from archive without extracting them

all the times we know need to extract an archive in order to see the archive content, if it is an large file its very difficult to extract and it takes lot of time to extract and required disk space as well to extract the files.

We have to use ‘-t’ option to see all files which are there in archive file

[root@TechTutorial tar]# tar -tf ravi.tar
d.txt
g.txt
kumar.txt
ravi.txt
tech.txt
test1.txt
test2.txt
test3.txt
test4.txt
Techtutorials.txt

5. Extract single file from archive

This option is very handy whenever we have an large archive file, we need only single file from that archive to be restored. In order to restore an single file from archive we have to use wildcards

[root@TechTutorial tar]# rm -rf *.txt  <<-- Deleted all the Files from current location
[root@TechTutorial tar]# ls   << -- After Deletion we have below files
3  arkit10.doc  arkit1.doc  arkit2.doc  arkit3.doc  arkit5.doc  arkit6.doc  arkit7.doc  arkit8.doc  arkit9.doc  ravi.tar
[root@TechTutorial tar]# tar -xvf ravi.tar Techtutorials.txt   <<<-- Restored an single file from archive
Techtutorials.txt
[root@TechTutorial tar]# ls   <<-- After Restoration we have below files
3            arkit1.doc  arkit3.doc  arkit6.doc  arkit8.doc  ravi.tar
arkit10.doc  arkit2.doc  arkit5.doc  arkit7.doc  arkit9.doc  Techtutorials.txt

above is the example how we can restore a single from archive

6. Extract multiple files from archive (not all files)

As you see in 5th step we extracted single file from archive, in the same way we are going to extract an multiple files from archive (not all).

Note: in order to extract files from archive you have to know exact file names, you can use ‘-t’ to see all the files in archive

[root@TechTutorial tar]# rm -rf Techtutorials.txt   <<-- To get clarity deleted previous presented files
[root@TechTutorial tar]# tar -xvf ravi.tar "Techtutorials.txt" "test1.txt"
test1.txt
Techtutorials.txt
[root@TechTutorial tar]# ls
3            arkit1.doc  arkit3.doc  arkit6.doc  arkit8.doc  ravi.tar           test1.txt
arkit10.doc  arkit2.doc  arkit5.doc  arkit7.doc  arkit9.doc  Techtutorials.txt
[root@TechTutorial tar]# rm -rf Techtutorials.txt test1.txt
[root@TechTutorial tar]# tar -xvf ravi.tar --wildcards *.txt
d.txt
g.txt
kumar.txt
ravi.txt
tech.txt
test1.txt
test2.txt
test3.txt
test4.txt
Techtutorials.txt

Note:: As we deleting the previous files only for demonstration only, DO NOT DELETE FILES in your environment.

you can mention multiple file names and also we can use wildcard option to restore multiple files as shown above example

7. Compressing files in gzip

As of now we see how to archive an files (grouping files together in single file). After creating an archive we did not get an space saving benefit because archive will not compress an files, file size will not decrease. When we compress an files we save disk space. If we want to create ‘gzip’ file with extension ‘.gz’ we have to use ‘-z’ option along with ‘tar’ command.

Let’s see an example

[root@TechTutorial tar]# tar -czvf tech.tar.gz *.txt
d.txt
g.txt
kumar.txt
ravi.txt
Techtutorials.txt
tech.txt
test1.txt
test2.txt
test3.txt
test4.txt
[root@TechTutorial tar]# ls
3            arkit2.doc  arkit6.doc  arkit9.doc  kumar.txt  tech.tar.gz        test1.txt  test4.txt
arkit10.doc  arkit3.doc  arkit7.doc  d.txt       ravi.tar   Techtutorials.txt  test2.txt
arkit1.doc   arkit5.doc  arkit8.doc  g.txt       ravi.txt   tech.txt           test3.txt
[root@TechTutorial tar]# du -h tech.tar.gz
4.0K    tech.tar.gz
[root@TechTutorial tar]# du -h *.txt
44K     d.txt
44K     g.txt
44K     kumar.txt
44K     ravi.txt
0       Techtutorials.txt
44K     tech.txt
44K     test1.txt
44K     test2.txt
44K     test3.txt
44K     test4.txt
[root@TechTutorial tar]#

As shown in above example, after compression of text files using ‘-z’ we got an compression file size is 4KB actual file size 380KB

8. Compressing files using bzip

Its also same like ‘gzip’ only but compression ratio of ‘.bz2′ is more compare to ‘.gz’ we are going to compress same files as we used in above example and see how much we will get the compressed file size, for ‘bzip’ we have to use ‘-j’ option.

[root@TechTutorial tar]# tar -cjvf 1tech.tar.bz2 *.txt
d.txt
g.txt
kumar.txt
ravi.txt
Techtutorials.txt
tech.txt
test1.txt
test2.txt
test3.txt
test4.txt
[root@TechTutorial tar]# du -h 1tech.tar.bz2
4.0K    1tech.tar.bz2

In this comparison of ‘.gz’ and ‘.bz2’ compression methods practical examples are below

9. Compression ratio of .gz (gzip) and .bz2 (bzip)

After compressing 34MB using ‘.gz’ output file size is 8.6MB.

Using same  files compressed with ‘.bz2’ output file size is 7.2MB. Comparatively .bz2 compression ratio is higher than .gz

[root@TechTutorial tar]# du -h tarr.tar.gz
8.6M    tarr.tar.gz
[root@TechTutorial tar]# du -h tarr.tar.bz2
7.2M    tarr.tar.bz2

10. Extracting compressed files from ‘gzip’ and ‘bzip’

To extract ‘gzip’ and ‘bzip’ files we have to use ‘-x’ option along with there own options ‘-z’ for gzip and ‘-j’ for bzip.

Below is the example for extracting the ‘bzip’ file

[root@TechTutorial tar]# tar -xjvf 1tech.tar.bz2
d.txt
g.txt
kumar.txt
ravi.txt
Techtutorials.txt
tech.txt
test1.txt
test2.txt
test3.txt
test4.txt

Below is the practical example for extracting the ‘gzip’ file

[root@TechTutorial tar]# tar -xzvf tech.tar.gz
d.txt
g.txt
kumar.txt
ravi.txt
Techtutorials.txt
tech.txt
test1.txt
test2.txt
test3.txt
test4.txt
[root@TechTutorial tar]#

11. zipping the files using zip command

zip command is used to compress the files with .zip extension, zip is available in different platform’s such as Unix, Linux, Windows and MAC.

Syntax:  zip <Destination File Path and Name>.zip  <source files to compress>

below is the example to compress the files using ‘zip’ command

[root@TechTutorial tar]# zip docfiles.zip *.txt
  adding: d.txt (deflated 100%)
  adding: g.txt (deflated 100%)
  adding: kumar.txt (deflated 100%)
  adding: ravi.txt (deflated 100%)
  adding: Techtutorials.txt (stored 0%)
  adding: tech.txt (deflated 100%)
  adding: test1.txt (deflated 100%)
  adding: test2.txt (deflated 100%)
  adding: test3.txt (deflated 100%)
  adding: test4.txt (deflated 100%)
[root@TechTutorial tar]#

12. zipping files and directories along with sub directories and its files

When we use remote directory compression using ‘zip’ command it will not compress all the sub directories and its content in order to compress all the sub directories and its files we have to use ‘-r’ along with zip command

[root@TechTutorial tar]# zip -r subdir.zip ravi/
  adding: ravi/ (stored 0%)
  adding: ravi/kumar/ (stored 0%)
  adding: ravi/kumar/tech/ (stored 0%)
  adding: ravi/kumar/tech/d.txt (deflated 100%)
  adding: ravi/kumar/tech/g.txt (deflated 100%)
  adding: ravi/kumar/tech/kumar.txt (deflated 100%)
  adding: ravi/kumar/tech/ravi.txt (deflated 100%)

13. compressing with high compression ratio

zip command has good feature that we can also mention an compression ratio option from 1 to 9. 9 gives high compression.

[root@TechTutorial tar]# zip -9 -r deepcompress.zip ravi/
  adding: ravi/ (stored 0%)
  adding: ravi/kumar/ (stored 0%)
  adding: ravi/kumar/tech/ (stored 0%)
  adding: ravi/kumar/tech/d.txt (deflated 100%)
  adding: ravi/kumar/tech/g.txt (deflated 100%)
  adding: ravi/kumar/tech/kumar.txt (deflated 100%)
  adding: ravi/kumar/tech/ravi.txt (deflated 100%)
  adding: ravi/kumar/tech/Techtutorials.txt (stored 0%)
  adding: ravi/kumar/tech/tech.txt (deflated 100%)
  adding: ravi/kumar/tech/test1.txt (deflated 100%)
  adding: ravi/kumar/tech/test2.txt (deflated 100%)
  adding: ravi/kumar/tech/test3.txt (deflated 100%)
  adding: ravi/kumar/tech/test4.txt (deflated 100%)

14. Excluding particular file / directory from compression

We can also exclude file from compression in order to do that ‘-x’ we have to use.

[root@TechTutorial tar]# zip -r compress1.zip ravi/ -x ravi/g.txt
  adding: ravi/ (stored 0%)
  adding: ravi/d.txt (deflated 100%)
  adding: ravi/kumar.txt (deflated 100%)
  adding: ravi/ravi.txt (deflated 100%)
  adding: ravi/Techtutorials.txt (stored 0%)
  adding: ravi/tech.txt (deflated 100%)
  adding: ravi/test1.txt (deflated 100%)
  adding: ravi/test2.txt (deflated 100%)
  adding: ravi/test3.txt (deflated 100%)
  adding: ravi/test4.txt (deflated 100%)
[root@TechTutorial tar]# ls ravi/
d.txt  g.txt  kumar.txt  ravi.txt  Techtutorials.txt  tech.txt  test1.txt  test2.txt  test3.txt  test4.txt

15. Delete particular file from zip

We can also delete an file from compressed file using option ‘-d’ along with zip command

[root@TechTutorial tar]# zip -d compress1.zip ravi/tech.txt
deleting: ravi/tech.txt

16. Update newly created files to zip

We can update zip file using ‘-u’ option which will only add newly created files to zip file.

[root@TechTutorial tar]# touch Update2.txt
[root@TechTutorial tar]# zip -u compress1.zip *.txt
  adding: Update2.txt (stored 0%)
[root@TechTutorial tar]#

17. Update zip with newly modified files

Update only modifed files to zip file, in order to do modified file update use ‘-fr’ option

[root@TechTutorial tar]# zip -fr compress1.zip *.txt
freshening: Update2.txt (stored 0%)
[root@TechTutorial tar]#

18. List all files from zip without extracting them

List all files from zip without extracting them

# less compress.zip

19. Check zip file content without extracting

Without extracting zip file, if you want to see zipped file content you can see using ‘zmore’ and ‘zless’ commands.

# zmore compress.zip
# zless comress.zip

20. De-compress zip file

In order to extract the zip file we have to use ‘unzip’ command. If files are exists it will ask you for the confirmation to re-write the same.

[root@TechTutorial tar]# unzip compress1.zip
Archive:  compress1.zip
replace d.txt? [y]es, [n]o, [A]ll, [N]one, [r]ename: y
  inflating: d.txt
replace g.txt? [y]es, [n]o, [A]ll, [N]one, [r]ename: y
  inflating: g.txt
replace kumar.txt? [y]es, [n]o, [A]ll, [N]one, [r]ename: A
  inflating: kumar.txt

20 useful tar and zip commands 20 useful tar and zip commands 20 useful tar and zip commands 20 useful tar and zip commands 20 useful tar and zip commands