Trying to install 3 different versions of Ubuntu for triple-boot (no Windows)

Solution 1:

1. No problem.
2. That is normal when you have 2 or more operating systems.

3. Pretty simple. Assume you have an empty disk and boot into the installation and are at the partitioning setup.

   • create 4 partitions. Ubuntu OS needs a root of about 25Gb that can include a /home/. 25Gb is more than enough if you keep your own data outside of the system (ie. out of / and out of /home).
   • mount the 1st of those 4 as /
   • mount the bottom one as /data/ or whatever name you want. Make it ext4.
   • install system 1.

• when done install system 2.
• mount the 2nd partition as /
• mount the bottom one as /data/ -without- formatting.

• when done install system 3
• mount the 3rd partition as /
• mount the bottom one as /data/ -without- formatting.

Some extras:

• Try to avoid sharing /home/.* and just stick to the subdirectories. This will avoid any kind of conflict between releases.
• if you want you can expand each of these with a boot.
• Opt for adding a partition for /opt. If you install 3rd party software that is the most ideal directory to use and there is a good chance you can then use the software on all 3.
• use the same usernames and userIDs on all systems.
• copy from 1 system all the directories in /home/ to /data/.
• When done remove all the -directories- in each of the /home/'s and edit .config/user-dirs.dirs in each of the systems to point to /data/.

And you are done.

I do believe though there is an easier method nowadays.

• Install 16.04 as explained at the 1st part with a /data/ disk. It is the latest LTS so has a long support.
• Install virtualBox or VM Ware. Install 2 systems into that.
• Install guestadditions for VBOX or WM Ware tools for VM Ware and mount the /data/ in the 2 systems.

Big plus for this: you can start all 3 systems at the same time. No picking a system at boot time. Adding more other operating systems is a lot easier an removing a system it also a lot easier. Backup means creating a copy of your container. And you can even multiply containers.

Solution 2:

I suggest you first install Ubuntu 14.04 and during installation make 3 partitions of 250gb ssd each disk formatted as ext4 and mount one partition as / , also format the other disk where you want to save data as /home . Then install Ubuntu 15.04 in the second partition of 250gb ssd and format it as ext4 and mount it as / and mount the other disk where you want to save data which is home for Ubuntu 14.04 as /home (no need to format it). Similarly install Ubuntu 16.04 on the third partition of 250gb ssd and mount it as / and mount the other disk which is used as home for other 2 Ubuntus as /home.

This way your home is mounted on other disk and data in that disk is shared among all Ubuntus. I have earlier used the same approach to share one home directory with Ubuntu and fedora. It will work fine.

Note: Keep username for all Ubuntu the same. You need to install grub and make sure it detects all OSes

Solution 3:

While you can do this, it may be more convenient to use chroot jails to hold your multiple installations of Ubuntu. This has a downside that you will need to use the same kernel for all of your installations, but the upside is that you can use them at the same time, without needing to reboot, and don't need to partition your disks for the individual installations.

There are full instructions on the Ubuntu wiki.