Hey, all!! I'm Rudrakshi back here with my new blog in which I'll be covering concepts and terminologies covered in the 4th session of #Linuxworkshop conducted by Pranav Jambare sir.

This blog presents information about Find and Locate command used in the Linux system and details about SSH.

Locate & Find

Find:

• Find is a command used to search for a file and directory.

• However, these files & directories can be searched on the basis of name, modification time, permission, and size.

• It can also find files or directories owned by a particular owner or group or by location.

• It can also be used to find files in the current directory or in a different directory.

• Basically, the find command is a very useful tool for finding files and directories on Linux systems.

• Find searches for your file recursively from a starting point that you specify

• Is more powerful and flexible, but slower and more resource intensive.

• Syntax:

    find [path] -[options]
  

• Different options:

  • "-name pattern": searches file on the basis of the name given.

  • "-type": searches file or directory on the basis of its given type.

  • "-user username": searches file on the basis of user name.

  • "-group groupname": searches file on the basis of the name of the group**.**

  • "-perm mode": searches files based on their permission.

  • "-exec command {} \;": executes a command on each matching file or directory.

  • "-inum": searches files based on their inode value.

  • "-size": searches on the basis of size provided.

Locate:

• Locate command is used to find files and directives quickly.

• Locate relies on a database that is maintained by an "updatedb" command.

• Locate searches a prebuilt database of files on your system, which makes it faster than the find command.

• the database allows locate command to find files or directories quickly without making it search the entire database.

• It is important to update database for acquiring latest changes and find files.

• Syntax:

locate [options] patter

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SSH

• SSH (Secure Shell) is a network protocol that allows users to connect safely and securely over an unsecured network.

• SSH is a protocol for remote communication in Linux.

• SSH is a widely used and supported protocol.

• SSH provides encryption for protecting data and authentication for user verification.

• For using SSH you need to install SSH-client on a local computer and SSH-server on a remote computer.

• Syntax:

    ssh username@IPaddress
  

• where username is the user name on a remote computer and "IP address" is the hostname of a remote computer.

SSH is used for secure file transfer, displaying graphics through remote systems, port sharing, and many more things.

SSH uses two types of keys:

Private Key:

• A private key is used to authenticate a user for a remote system.

• It is used to verify a user's identity.

• It is kept private by the user it is recommended to not share it with anyone for your system's security.

• Private keys are used to secure SSH connections.

Public Key:

• A public key is a cryptographic key used for the authentication of users to the remote system.

• A public key is mainly stored on a remote system in a file called "authorized_key" which is located in the user's home directory.

• The public key is copied to the remote system and added to the "authorized_key" file while the private key is kept on the user's local system.

• Using public key authentication is more secure than a password, as there is no need to transmit a password over a network.

Assembling SSH connection:

• For the creation of SSH connection systems need to have these two important packages installed.

  1. openssh-client

  2. openssh-server

• The Syntax for Installing Packages:

    $ yum install [packagename]
    # $ yum install openssh-server
    # $ yum install openssh-client
  

• The syntax for checking port 22:

    $ netstat -tunlp|grep 22
  

• The syntax for checking the status of service:

    $ systemctl status [serviceName]
    #e.g.systemctl status sshd
  

• The syntax for starting the service:

    $ systemctl start [serviceName]
  

• The syntax for stopping the service:

    $ systemctl stop [serviceName]
  

• The syntax for restarting the service:

    $ systemctl restart [serviceName]
  

• The syntax for connecting servers remotely:

    $ ssh username@hostid
    # ssh rsawant@132.167.122.1
  

• The Syntax for allowing/denying users to connect with a specific server:

    #use the following command to visit configuration file
    $ vim /etc/ss/sshd_config
    #then add
    $ AllowUser [username] or $ DenyUser [username]
    #after adding save and restart the service and then check the status