#### joshmccraney

Hi PF!

I'm trying to switch to Ubuntu 14.04.5. Currently I am running Ubuntu 18. How do you recommend I do this; do I have to uninstall Ubuntu, reinstall Windows, and then go to 14?

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#### PeterDonis

Mentor
I'm trying to switch to Ubuntu 14.04.5
Is there a particular reason why you want to go back this far? This version's support period expired in April 2019.

do I have to uninstall Ubuntu, reinstall Windows, and then go to 14?
If you have all your data backed up on separate media, you can just run the Ubuntu installer from CD/DVD (or USB stick if you have one) and tell it to reformat your hard drive. That will erase whatever you currently have installed.

#### joshmccraney

Is there a particular reason why you want to go back this far?
Yea, I'm running a CFD software called OpenFOAM and a particular component only works on an older version of the software, which only runs on an older version of Ubuntu.

If you have all your data backed up on separate media, you can just run the Ubuntu installer from CD/DVD (or USB stick if you have one) and tell it to reformat your hard drive. That will erase whatever you currently have installed.
Can you elaborate here (I'm not too great with computers). How do I tell it to reformulate the HD? When I first installed Ubuntu I did it from the previous Windows that the computer was running. But I'm unsure how to do this from Ubuntu.

#### PeterDonis

Mentor
I'm running a CFD software called OpenFOAM and a particular component only works on an older version of the software, which only runs on an older version of Ubuntu
Have you considered running the older version of Ubuntu inside a virtual machine? Virtualbox will do that. You can install virtualbox from the Ubuntu 18 package manager, and then run it and install Ubuntu 14 in a virtual machine.

How do I tell it to reformulate the HD?
If you boot the computer from the Ubuntu install CD/DVD, and it detects an existing installation on your hard drive, it will give you several options, one of which will be something like "Erase disk and install Ubuntu". That's the one to choose if you want to reformat the hard drive. Note that this will erase everything that's currently on your hard drive, including your existing Ubuntu 18 installation.

When I first installed Ubuntu I did it from the previous Windows that the computer was running.
How did you do that? Did you boot the computer from an Ubuntu install CD/DVD? Or something else?

#### joshmccraney

Have you considered running the older version of Ubuntu inside a virtual machine? Virtualbox will do that. You can install virtualbox from the Ubuntu 18 package manager, and then run it and install Ubuntu 14 in a virtual machine.
I thought about this a while ago, but the CFD software is very slow on a virtual machine.

If you boot the computer from the Ubuntu install CD/DVD, and it detects an existing installation on your hard drive, it will give you several options, one of which will be something like "Erase disk and install Ubuntu". That's the one to choose if you want to reformat the hard drive. Note that this will erase everything that's currently on your hard drive, including your existing Ubuntu 18 installation.
I actually can't use a CD/DVD, though I have a thumbdrive that's worked before.

How did you do that? Did you boot the computer from an Ubuntu install CD/DVD? Or something else?
I booted from an external HD. I had to formulate the HD so it was bootable (from Windows, which is what I was running) and then restarted the computer in a weird way. Does this sound familiar at all?

#### PeterDonis

Mentor
I actually can't use a CD/DVD, though I have a thumbdrive that's worked before.
Ok, that would work the same as far as the installer goes.

I booted from an external HD. I had to formulate the HD so it was bootable (from Windows, which is what I was running) and then restarted the computer in a weird way. Does this sound familiar at all?
I'm not sure. I've always used either a CD/DVD or a bootable USB drive and just booted the Ubuntu installer from that. (The Ubuntu installer is just a version of the appropriate Ubuntu system that boots from CD/DVD or USB stick, and then runs the installer program from the booted Ubuntu system.)

If the external HD is bootable and has Ubuntu on it, and it was connected to the computer by USB, it would be the same as booting from a USB drive.

You might also have had to make changes in your computer's BIOS or UEFI firmware when you booted from the external HD the first time. I don't know if that's what you mean by restarting "in a weird way". Did you reformat the computer's internal HD when you did this? Or do you boot from the external HD whenever you want to boot Ubuntu 18, and then just unplug the external HD and reboot in Windows?

#### pbuk

I don't think I would do this, switching back to 14.04 might solve this problem, but it might create some new ones too!

What openFOAM package is causing the problem?

#### joshmccraney

Ok, that would work the same as far as the installer goes.

I'm not sure. I've always used either a CD/DVD or a bootable USB drive and just booted the Ubuntu installer from that. (The Ubuntu installer is just a version of the appropriate Ubuntu system that boots from CD/DVD or USB stick, and then runs the installer program from the booted Ubuntu system.)

If the external HD is bootable and has Ubuntu on it, and it was connected to the computer by USB, it would be the same as booting from a USB drive.

You might also have had to make changes in your computer's BIOS or UEFI firmware when you booted from the external HD the first time. I don't know if that's what you mean by restarting "in a weird way". Did you reformat the computer's internal HD when you did this? Or do you boot from the external HD whenever you want to boot Ubuntu 18, and then just unplug the external HD and reboot in Windows?
I've reformatted the internal HD, so it always boots as Ubuntu.

And I'll give it a whirl tomorrow (today is busy) and see if it works. Thanks for your help, I really appreciate it!

#### joshmccraney

I don't think I would do this, switching back to 14.04 might solve this problem, but it might create some new ones too!

What openFOAM package is causing the problem?
In the Dambreak tutorial, turning off gravity implies surface tension is dominant, and thus contact angles dictate flow. The build in alphaContactAngle contact angle models are aphysical. So I want to employ the Kistler contact angle model. But I'm having difficulty getting it to work on Ubuntu 18, but a recent lab graduate did it in Ubuntu 14.

I have the .C and .H files, but cannot seem to get FOAM to work with them.

#### pbuk

So I want to employ the Kistler contact angle model. But I'm having difficulty getting it to work on Ubuntu 18, but a recent lab graduate did it in Ubuntu 14.
I am not sure that this has anything to do with Ubuntu versions, more likely the 'recent lab graduate' had installed the latest version of OpenFOAM from its own repository using the instructions at https://openfoam.org/download/7-ubuntu/. If you didn't do that and just did sudo apt install openfoam you will get a very old version.

#### pbuk

Jusy read through again; you only have the source files and even if OpenFOAM can deal with this it probably expects the gcc compiler and other build tools to be installed which they won't be on a new install. Are you getting any error messages that might point at the problem(s)?

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