Remote Copying Tools, Archiving Tools, Backup & User Management

These are the topics that are covered in today's session.

Pranav Jambare

Remote Copying Tools:

1 . SCP :

• SCP stands for secure copy command in Linux.

• It is used to copy the files between the servers securely.

• It allows the secure transfer of files between the local host and the remote host or between two remote hosts.

#Syntax :
scp <filename> <remoteuser>@<remoteuserIP>:<destination>

#Example:
scp myLinuxFile root@192.168.100.7:/root

2 . RSYNC:

• RSYNC stands for remote synchronisation command in Linux.

• It synchronizes files from a source to a destination.

• It is famous for its delta-transfer algorithm, which reduces the amount of data sent over the network by sending only the differences between the source files and the existing files in the destination.

• RSYNC finds files that need to be transferred using a checksum algorithm that looks for files that have changed in size or in the last-modified time.

#Syntax:
rsync -av <filename> <remoteuser>@<remoteuserIP>:<destination>

#Example:
rsync -av myLinuxFile root@192.168.100.7:/root

3 . SFTP:

• SFTP stands for Safe File Transfer Protocol.

• It is a secure variant of FTP.

• It is a part of the SSH Protocol and is designed to securely transfer files between remote systems via a network connection.

#Syntax:
sftp <username>@<userIP>

#Example:
sftp linuxUser@192.168.100.7

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Archiving Tools:

• Archiving is the process of combining multiple files into a single package called an archive.

• This archive can then be easily backed up, or simply kept on your machine as a way to organize your file system.

1 . gzip

#Syntax : (Compress)
gzip <filename>

#Example : 
gzip myFile

#Syntax : (Decompress)
gunzip <filename>.gz

#Example : 
gunzip myFile.gz

2 . xz

#Syntax: (Compress)
xz <filename>

#Example:
xz myFile

#Syntax: (Decompress)
unxz <filename>.xz

#Example:
unxz myFile.xz

3 . bzip2

#Syntax: (Compress)
bzip2 <filename>

#Example:
bzip2 myFile

#Syntax: (Decompress)
bzip2 <filename>.bz2

#Example:
bzip2 myFile.bz2

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Backup:

Fig. Regular files being added to an archive with tar and then compressed with gzip.

• The tar utility is also able to compress an archive via a compression tool.

• To create an archive file :

#Syntax:
tar -cvzf <destn.backup> <sourcefile>

#Example:
tar -cvzf myLinuxFile.backup file1 file2 file3

• To extract an archive file:

#Syntax:
tar -xvf <destn.backup>

#Example:
tar -xvf myLinuxFile.backup

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User Management:

• A user is an entity, that can manipulate files and perform several other operations.

• Each user is assigned an ID that is unique for each user in the operating system.

• The ID 0 is assigned to the root user and the IDs 1 to 999 are assigned to the system users, hence the ids for the local user begin from 1000 onwards.

1 . Adding the User :

• The command "useradd" or "adduser" can be used to create a new user in Linux also, the sudo permissions are required to perform this command.

    #Creating a User:
    root@myLinux:~# useradd testuser
    #OR
    root@myLinux:~# adduser testuser
  

2 . Verifying the User:

root@myLinux:~# id testuser
uid=1001(testuser) gid=1001(testuser) groups=1001(testuser)

3 . Deleting the User:

root@myLinux:~# userdel testuser

4 . Managing the password policy:

Fields of /etc/password file:

#The sudo permissions are required to perform this command
root@myLinux:~# cat /etc/passwd|tail -1
testuser:x:1001:1001::/home/testuser:/bin/sh

Where,

testuser --> Name of user

x --> Encrpyted password

1001 --> User id

1001 --> Group id

:: --> Nickname (Con-name)

/home/testuser --> Home directory of the user

/bin/bash --> Default shell of user

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Setting the password :

#The sudo permissions are required to perform this command
root@myLinux:~# passwd testuser
#Next...
New password: 123 
Retype new password: 123
passwd: password updated successfully

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Changing the password policy:

root@myLinux:~# chage -M 2 -m 5000 -W 4 -I 12 -E 2024-12-2

Where,

-M --> maxdays password change date

-m --> mindays password change date

-W --> warning

-I --> Inactivity

-E --> Account Expiry date

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5 . Change / Restrict the User:

Give "No Login" to the User:

root@myLinux:~# usermod testuser -s /sbin/nologin

#Verifying...
root@myLinux:~# su - testuser
Cannot change directory to /home/testuser:   
No such file or directory
This account is currently not available.

To revert the changes to get a login:

root@myLinux:~# usermod testuser -s /bin/sh

#Verifying...
root@myLinux:~# su - testuser
Last Login : .....
$whoami
testuser

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6 . Lock and Unlock User:

# To Lock the user:
root@myLinux:~# usermod -L testuser

# To Unlock the user:
root@myLinux:~# usermod -U testuser

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7 . Adding Group:

#The sudo permissions are required to perform this command
root@myLinux:~# groupadd testgroup

#Verifying the group...
root@myLinux:~# cat /etc/group|tail -1   
testgroup:x:1002:

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8 . Adding a user to a group:

root@myLinux:~# usermod -G testgroup testuser 

#Verifying...
root@myLinux:~# id testuser
uid=1001(testuser) gid=1001(testuser) groups=1001(testuser),1002(testgroup)

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9 . Deleting a group:

root@myLinux:~# groupdel testgroup

#Verifying...
root@myLinux:~# id testuser
uid=1001(testuser) gid=1001(testuser) groups=1001(testuser)

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10 . Change the user-id of the user:

root@myLinux:~# usermod -u 1005 testuser

#Verifying...
root@myLinux:~# id testuser
uid=1005(testuser) gid=1001(testuser) groups=1001(testuser)

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