📦 Cloning an Ubuntu System Using SSH and `dd`

📚 Table of Contents

• 📚 Table of Contents
• 📚 Introduction
• 🎯 Benefits of Using SSH for Cloning
• 🔧 Prerequisites
• ⚠️ Disclaimer
• 👣 Step-by-Step Guide
  • 1. 📊 Diagram and Network Configuration
  • 2. 🔄 Preparation on Destination Server
  • 3. 🚀 Set Up tmux on Client Machine
  • 4. 💾 Perform dd Clone
  • 5. 🔄 Post-cloning Procedures on Destination Server
  • 6. 🔍 Verify MD5 Checksums
• 🎉 Conclusion

📚 Introduction

System cloning is an essential task that ensures a smooth migration of data and settings from one machine to another. This guide will walk you through the process of cloning an Ubuntu system from Source Server to Destination Server using SSH and dd. Leveraging SSH provides a secure and encrypted data transfer channel between the two systems, making it a reliable choice for IT professionals.

Note

In a lab environment, both machines are on the same network. However, in a real-world scenario, as long as Source Server and Destination Server can SSH into each other, they can be located on different networks.

🎯 Benefits of Using SSH for Cloning

• 🤑 Cost-Effective: Uses existing network infrastructure; no need for additional hardware.
• 🔒 Secure: SSH encrypts data across the network, reducing risks of interception.
• ⏳ Minimal Downtime: Cloning over SSH can be performed remotely, offering flexibility and reducing system downtime.
• 🆓 Open Source Server: Both SSH and dd are open-Source Server tools available on most Linux distributions without additional licensing costs.

🔧 Prerequisites

• Two Ubuntu server machines (source and destination server).
• One client machine for remote connection.
• Destination Server should boot from a Live CD for system configuration.
• Ensure network connectivity between all machines.
• SSH access configured between machines.
• Install tmux on the client machine to prevent disconnects during long operations.

⚠️ Disclaimer

Warning

This guide is provided as-is without any warranties. The authors are not responsible for any damage or data loss that may occur. It is highly recommended to back up your system thoroughly before proceeding. Practice on a lab environment before applying these steps in a production environment.

👣 Step-by-Step Guide

1. 📊 Diagram and Network Configuration

• Diagram:

sequenceDiagram
    participant Client
    participant Source Server
    participant Destination Server

    Client->>Source Server: SSH connection to Source Server
    Client->>Source Server: Start tmux session
    Client->>Source Server: Execute dd command
    Source Server->>Destination Server: Transfer disk image via SSH
    Destination Server->>Source Server: Acknowledge data receipt
    Client->>Destination Server: SSH connection to Destination Server
    Client->>Destination Server: Activate LVM volumes
    Client->>Destination Server: Mount partitions
    Client->>Destination Server: Update /etc/fstab
    Client->>Destination Server: Check MD5 checksum
    Client->>Destination Server: Reinstall GRUB
    Client->>Destination Server: Reboot system
    Source Server ->> Client: Check MD5 checksum
    Destination Server ->> Client: Compare MD5 checksums

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Source Server Specs

blkid
/dev/sda2: UUID="8c25bceb-6a04-45d8-9e60-f786fe1e0778" TYPE="ext4" PARTUUID="9a3b0e19-8322-4f5e-9edc-f90b65738d0b"
/dev/sda3: UUID="IZvTo7-LaTh-hX6U-udHF-rchA-heeq-ft6Xla" TYPE="LVM2_member" PARTUUID="be13df45-0673-48d1-9bda-dc3ae8516805"
/dev/mapper/ubuntu--vg-ubuntu--lv: UUID="015ffb9a-4b73-4010-9b73-854ddd6e8c55" TYPE="ext4"

lsblk
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT       
loop0                       7:0    0 91.9M  1 loop /snap/lxd/24061  
loop1                       7:1    0 63.3M  1 loop /snap/core20/1828
loop2                       7:2    0 49.9M  1 loop /snap/snapd/18357
loop3                       7:3    0 38.8M  1 loop /snap/snapd/21759
loop4                       7:4    0   64M  1 loop /snap/core20/2379
loop5                       7:5    0 91.9M  1 loop /snap/lxd/29619  
sda                         8:0    0   25G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0    2G  0 part /boot
└─sda3                      8:3    0   23G  0 part
  └─ubuntu--vg-ubuntu--lv 253:0    0 11.5G  0 lvm  /
sr0                        11:0    1 1024M  0 rom

Destination Server Specs

lsblk
NAME  MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
loop0   7:0    0   2.2G  1 loop /rofs
loop1   7:1    0     4K  1 loop /snap/bare/5
loop2   7:2    0  63.3M  1 loop /snap/core20/1828
loop3   7:3    0 346.3M  1 loop /snap/gnome-3-38-2004/119   
loop4   7:4    0    46M  1 loop /snap/snap-store/638        
loop5   7:5    0  91.7M  1 loop /snap/gtk-common-themes/1535
loop6   7:6    0  49.9M  1 loop /snap/snapd/18357
sda     8:0    0    25G  0 disk
sr0    11:0    1   4.1G  0 rom  /cdrom

• Ensure that SSH is installed and configured on both Source Server and Destination Server. Verify network connectivity:
• Ping Source Server and Destination Server from the client machine to ensure connectivity.
• Set up SSH keys for password-less login if needed.

2. 🔄 Preparation on Destination Server

Ensure Destination Server is prepared to receive the disk image:

1. Update package lists and install necessary tools (lvm2, grub-pc).
2. Boot from a Live CD and ensure all partitions are unmounted.

⚠️ Note: Double-check the network connection before proceeding.

3. 🚀 Set Up tmux on Client Machine

On the client machine, open a tmux session to manage the SSH connection. Using tmux ensures that your session remains active even if the network connection is interrupted:

1. Connect to Source Server using SSH from the client.
2. Start a tmux session by running tmux.

Important: Using tmux helps prevent disruptions during long operations, ensuring a smooth and uninterrupted cloning process.

4. 💾 Perform dd Clone

Using SSH, clone the disk from Source Server to Destination Server:

• From the client machine, within the tmux session, execute:

  sudo dd if=/dev/sda bs=64K conv=noerror,sync status=progress | ssh ubuntu@[Destination Server IP] "sudo dd of=/dev/sda bs=64K status=progress"

🔗 Important: Ensure SSH service is running and using tmux on both machines.

5. 🔄 Post-cloning Procedures on Destination Server

After cloning, perform system setup on Destination Server:

• Activate LVM Volumes:

  sudo vgscan
  sudo vgchange -ay

• Mount the Partitions:

  sudo mkdir -p /mnt/root
  sudo mount /dev/mapper/ubuntu--vg-ubuntu--lv /mnt/root
  sudo mkdir -p /mnt/root/boot
  sudo mount /dev/sda2 /mnt/root/boot

• Check UUIDs using blkid

  lsblk
  NAME                      MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
  loop0                       7:0    0   2.2G  1 loop /rofs
  loop1                       7:1    0     4K  1 loop /snap/bare/5
  loop2                       7:2    0  63.3M  1 loop /snap/core20/1828
  loop3                       7:3    0 346.3M  1 loop /snap/gnome-3-38-2004/119
  loop4                       7:4    0    46M  1 loop /snap/snap-store/638
  loop5                       7:5    0  91.7M  1 loop /snap/gtk-common-themes/1535
  loop6                       7:6    0  49.9M  1 loop /snap/snapd/18357
  sda                         8:0    0    25G  0 disk
  ├─sda1                      8:1    0     1M  0 part
  ├─sda2                      8:2    0     2G  0 part             
  └─sda3                      8:3    0    23G  0 part
  └─ubuntu--vg-ubuntu--lv 253:0    0  11.5G  0 lvm
  sr0                        11:0    1   4.1G  0 rom  /cdrom
  
  blkid
  /dev/sr0: UUID="2023-03-16-15-57-27-00" LABEL="Ubuntu 20.04.6 LTS amd64" TYPE="iso9660" PTUUID="405a23c7" PTTYPE="dos"     
  /dev/loop0: TYPE="squashfs"
  /dev/loop1: TYPE="squashfs"
  /dev/loop2: TYPE="squashfs"
  /dev/loop3: TYPE="squashfs"
  /dev/loop4: TYPE="squashfs"
  /dev/loop5: TYPE="squashfs"
  /dev/loop6: TYPE="squashfs"
  /dev/sda1: PARTUUID="6534e633-d1a1-43e3-82f2-a5f5fb7b5379"
  /dev/sda2: UUID="8c25bceb-6a04-45d8-9e60-f786fe1e0778" TYPE="ext4" PARTUUID="9a3b0e19-8322-4f5e-9edc-f90b65738d0b"
  /dev/sda3: UUID="IZvTo7-LaTh-hX6U-udHF-rchA-heeq-ft6Xla" TYPE="LVM2_member" PARTUUID="be13df45-0673-48d1-9bda-dc3ae8516805"
  /dev/mapper/ubuntu--vg-ubuntu--lv: UUID="015ffb9a-4b73-4010-9b73-854ddd6e8c55" TYPE="ext4"

• Edit UUID in /etc/fstab

  sudo nano /mnt/root/etc/fstab

  # /etc/fstab: static file system information.
  #
  # Use 'blkid' to print the universally unique identifier for a
  # device; this may be used with UUID= as a more robust way to name devices
  # that works even if disks are added and removed. See fstab(5).
  #
  # <file system> <mount point>   <type>  <options>       <dump>  <pass>
  # / was on /dev/ubuntu-vg/ubuntu-lv during curtin installation
  UUID=015ffb9a-4b73-4010-9b73-854ddd6e8c55 / ext4 defaults 0 1
  # /boot was on /dev/sda2 during curtin installation
  UUID=8c25bceb-6a04-45d8-9e60-f786fe1e0778 /boot ext4 defaults 0 1
  /swap.img       none    swap    sw      0       0

• Reinstall GRUB for boot configuration:

  sudo mount --bind /dev /mnt/root/dev
  sudo mount --bind /proc /mnt/root/proc
  sudo mount --bind /sys /mnt/root/sys
  sudo chroot /mnt/root
  grub-install /dev/sda
  update-grub
  exit

• Clean up and reboot the system:

  sudo umount /mnt/root/dev /mnt/root/proc /mnt/root/sys /mnt/root/boot /mnt/root
  sudo reboot

MD5 Checksums

6. 🔍 Verify MD5 Checksums

After rebooting, verify the integrity of the cloned data by comparing MD5 checksums on both Source Server and Destination Server:

• On Source Server, generate MD5 checksums

  sudo md5sum /dev/sda2 /dev/sda3 /dev/mapper/ubuntu--vg-ubuntu--lv > /tmp/source_md5.txt

• On Destination Server, generate MD5 checksums

  sudo md5sum /dev/sda2 /dev/sda3 /dev/mapper/ubuntu--vg-ubuntu--lv > /tmp/destination_md5.txt

• Transfer the checksum files to the client machine and compare them using diff

  scp ubuntu@[Source Server IP]:/tmp/source_md5.txt /tmp/
  scp ubuntu@[Destination Server IP]:/tmp/destination_md5.txt /tmp/
  diff /tmp/source_md5.txt /tmp/destination_md5.txt

If there are no differences, the cloning process is complete and successful.

🎉 Conclusion

You've successfully cloned an Ubuntu system using SSH and dd. This process ensures a secure and reliable migration with minimal downtime. By following these steps, you're leveraging both the power and flexibility of Linux and open-Source Server tools.

🔔 Final Note: Verify that all settings and data have transferred correctly after rebooting. Both Source and Destination Server are the same packages, settings. GL & HF!