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CatMan
Asked: 2019-12-14 05:36:50 +0800 CST

How can I run the Ubuntu installer from another installation

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This is what I have and what I want to achieve:

 Current Partition Setup   Current State         Desired State  

 /dev/sda1   /BIOS
 /dev/sda2   /             Ubuntu18.04           Ubuntu18.04 I
 /dev/sda3   empty         none                  Ubuntu18.04 II

In want to install Ubuntu 18.04 II from my running installation Ubuntu 18.04. I.

  • I have an ISO install file.

What else do I need and how do I do it?

There is a similar question, Is there a program to install Ubuntu from a Linux system? It uses debootstrap and targets minimal Ubuntu systems and text only installs. Its a very complex setup. I am looking for sth saving the time and effort to reboot.

The key point of my question is that I do not want to shut down or reboot my computer.

I want to boot into /dev/sda1 and start an application/a script/single commands or whatever. After that Ubuntu18.04 II should be installed in /dev/sda3. And I am still in my running install on /dev/sda1.

system-installation

2 Answers

  1. Since you have already instaled one partition, you can use the same bootable media to install on the other partition.

    Plug in your bootable Ubuntu USB, restart the PC and boot the Live CD. Once the Live CD is booted up, start the installation. The installation screen will start.

    1. Select the keyboard layout
    2. On the next screen, the installation will prompt you to install additional drivers, codecs etc.
    3. Formating partitions and dual boot setup This is a very important screen. On this screen, we need to choose how Ubuntu will install. Select the first option which says Install Ubuntu alongside Ubuntu.
    4. Now click continue, on this screen, you need to set up partitions and hard disk space. First, you need to select the drive on which we are installing Ubuntu. On this screen, there will be a graphic representation of our Ubuntu OS and Ubuntu installation and how much space they have or will get after we finish setting up the partitions.
    5. After you finished setting the partitions, click continue and you will get a prompt with a popup and it will ask us to confirm the changes.
    6. Next step is to set up the user account and computer name.
    7. After you set up the user account, the installation will start and it will take some time.
    8. Once the installation is finished, you’ll get a prompt again and it will ask to restart the PC. Remove the bootable USB and restart the PC.
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  2. https://help.ubuntu.com/community/Installation/FromLinux specifies "You may run the Ubuntu Desktop installer directly from your hard drive..." in its third paragraph. It specifies exactly what steps to perform in which order.

    You may also wish to consider creating a swap partition, and telling each Ubuntu version to use it in lieu of a swap file; erase it at shutdown and reboot. That way, you would use less space for swap, as opposed to a swap file occupying space in /sda2 and /sda3.

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