Task Sesi 4: Linux and Unix Administration 2

Project Challenge

Project Challenge

1. Set up 2 servers on VirtualBox
2. Configure the 2 servers to connect via SSH without a password
3. Create a file named server1.txt on server1
4. Create a cron job to automate sending the server1.txt file from server1 to server2 at a specified interval

Step 1: Setup Two Servers

Since i am using MacOS i will use UTM to set up my virtual machine. I will use Ubuntu 24.04 LTS as my server. For details my server setup:

	Server 1	Server 2
user	u24-1	u24-2
server-name	u24-1	u24-2
IP	192.168.64.9	192.168.64.8
OS	Ubuntu 24.04 LTS	Ubuntu 24.04 LTS
RAM	2 GB	2 GB

Setup Server Already success

left side is server1 and right side is server2. Both server successfully setup and i can access both server using SSH.

Step 2: Configure Passwordless SSH

Workflow

sequenceDiagram
    participant S1 as Server 1
    participant S2 as Server 2

    S1->>S1: ssh-keygen -t rsa
    Note over S1: Generates:<br>~/.ssh/id_rsa (private)<br>~/.ssh/id_rsa.pub (public)

    S1->>S2: ssh-copy-id u24-2@192.168.64.8
    Note over S2: Adds Server 1's public key to<br>~/.ssh/authorized_keys

    S1->>S2: ssh u24-2@192.168.64.8
    Note over S1,S2: Passwordless SSH successful

    S2->>S2: ssh-keygen -t rsa
    S2->>S1: ssh-copy-id u24-1@192.168.64.9
    S2->>S1: ssh u24-1@192.168.64.9
    Note over S1,S2: Bidirectional passwordless SSH

On Server 1

1. Generate an SSH key pair:

   ssh-keygen -t rsa
   

   More Detail

   this command will generate 2 key (files):

   • private key: ~/.ssh/id_rsa

     private key is secret key, should be kept secret. DO NOT SHARE THIS KEY

   • public key: ~/.ssh/id_rsa.pub

     public key is the key that you can share to other server. This key will be used to verify your identity.

2. Copy the public key to Server 2:

   ssh-copy-id u24-2@192.168.64.8
   

   This command will copies your public SSH key (located: ~/.ssh/id_rsa.pub) to the remote server's authorized_keys file.

   or manually copy the public key to server2

   cat ~/.ssh/id_rsa.pub
   # output:
   # ssh-rsa AAAAB3NzaC1y..../FgWNXulrHoe7rew== u24-1@u24-1
   

   Copy the output and paste it to ~/.ssh/authorized_keys on server2

   # login to server2
   ssh u24-2@192.168.64.8
   
   # we are on server2 right now
   mkdir -p ~/.ssh # if not exist
   # paste the public key to ~/.ssh/authorized_keys
   echo "ssh-rsa AAAAB3NzaC1yc2E...banyak karakter...user@server1" >> ~/.ssh/authorized_keys
   

On Server 2

It same as above: Generate an SSH key pair and copy the public key to Server 1

ssh-keygen -t rsa
ssh-copy-id u24-1@192.168.64.9

Step 3: Create server1.txt on Server1

On Server 1, I created a dynamic file that updates every minute:

crontab -e

Add this line:

*/1 * * * * echo "Hello World! Waktu: $(date)" >> /home/u24-1/server1.txt

This appends a timestamped message to /home/u24-1/server1.txt every minute because of */1 in the first column.

Step 4: Automate File Transfer with Cron

On Server 1, set up a cron job to copy server1.txt to Server 2 every 5 minutes:

crontab -e

Add this line:

*/5 * * * * scp /home/u24-1/server1.txt u24-2@192.168.64.8:/home/u24-2

• scp securely copies the file over SSH.
• Check log cron using grep CRON /var/log/syslog | tail -5. It will show the last 5 cron jobs.

Full Crontab Configurate

*/1 * * * * echo "Hello World! Waktu: $(date)" >> /home/u24-1/server1.txt
*/5 * * * * scp /home/u24-1/server1.txt u24-2@192.168.64.8:/home/u24-2

Result

left side is server1 and cron job that will append Hello World! Waktu: $(date) to server1.txt every minute. and cron job that will copy server1.txt file from Server 1 to Server 2 every 5 minutes.

right side is server2 and will see the result of server1.txt file that copied from server1. after waiting another 5 minutes, the condition will be like this:

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