Linux_Questions

1. Provide steps to create a directory inside a directory where the parent directory does not exist.
Ans: mkdir -p dirA/dirB/dirC

2. How to install a package on a Linux server when there is no internet connection?
Ans: For this we must have ssh connection to the server, so we can copy the files and build them right there in the server and we can install that package or we can copy the binaries.
On the server having internet we can download .deb package and it's dependencies.
We can transfer those file via scp on the server with No Internet. Then we can install the package on the server with No Internet (dpkg -i /path_to_directory/package_name.deb)


3. How to access specific folders of Server A from Server B and Server C?
Ans: 
* NFS (Network File System):
     Network File System is a distributed file system protocol that allows us to mount remote directories on your server. It is ideal, where the shared resources must be accessed regulary.
	We will have to setup the NFS for the host as well as the client server individually.
	For the host server, first, we will have to create the shared directory. This can achieved by configuring a general purpose mount(/var/nfs/general), exporting the home directory.Then we will have to configure the NFS exports(/etc/exports) and we will have to adjust the firewall of the host server.
	For the client server, we will have to create mount points and mounting directories.
	We can test the setup by running the command from the host server.

* SSH Connection-
    Access Server A from Server B:
    From server B: ssh username@A_IP

    Access Server A from Server B:
    From server C: ssh username@A_IP
*FTP Connection:
  To access the specific folders of a Server we can setup FTP Server:
  TO achieve that, 
      - make the changes in vsftpd configuration file
      - open the port 22 in firewall
      - we can create a user directory and set the permission
      - we can connect to the server A from server B(where the FTP server is configured) using the command [ftp <IP_of Server_A]

4. How to check all the running processes from a server?
Ans: Command is:
        ps --> displays information about active processes
        top --> displays dynamic real-time information about running processes.

5. Provide the command to delete all the files older than X days inside a specific directory.
Ans: find /path/to/directory -type f -mtime +X -delete
	      Where path/to/directory: the directory where the file is located at
	      X: no of days

6. Create a shell script to identify the process ID a. script should as a user input for process ID b. If the process exists, the script should print the process ID and exit c. If the process doesn't exist script should print the process doesn't exist and asks for another input
Ans: 
#!/bin/bash
while true; do
    # Ask the user for the PID
    read -p "Enter the PID of the process you want to check (or 'q' to quit) " pid
    if [ "$pid" == "q" ]; then
            echo "Exiting from the script"
            exit 0
    fi
# Check if the process exists

if ps -p $pid > /dev/null; then
    echo "Process with PID $pid is running."
else
    echo "Process with PID $pid is not running."
fi
done