I want to install an older version (17) on the same HD and have both 17 & 20 access the same - or a new - data partition. What's the best way to do this? Preferably /home/username would be the same on both systems.
You are aware of the potential pitfalls in sharing $HOME between two different OSes?
FYI: This box is dual boot; I have 2x OSes installed (Ubuntu lunar
or the development release, and Ubuntu jammy
or the LTS release). I've always liked dual boot; and consequently felt sharing $HOME was great... long ago anyway.
I've done what you're trying to do in the past, back in late 2000's (Ubuntu 10.10 days maybe) I'd experienced few issues with it in the years before then anyway.. However in the following few release cycles I stopped doing it, unless I did a ton of homework
to ensure I didn't suffer data loss.
eg. in 2011 changes were made in GNOME that provided newer features in the GNOME MUA (Evolution or mail user agent program) & other GNOME apps, I decided those features were terrific & started using them on the newer OS, and since the other (older) OS didn't know about those features; I just assumed it wouldn't be an issue... I learnt many
weeks later it was!
Eventually I was notified I was ignoring (not replying
etc to emails) from multiple people, which had me explore why... Turns out by using the feature in my MAIL program on the newer release; it caused emails to be completely ignored by the older program; no errors - just the data it showed was incomplete... I'd not done my homework on that new feature; looked at what change it would do to the datafiles, and how that change would impact the older version of the program (the older app ignored data records that used the new feature & one record before/after too
I've given one example here only; sorry if you don't understand.. but the consequences can be significant... In my case it was a matter of weeks (6-8 weeks) before I noted the problem; and I quickly discovered when using the older OS I could read my emails via jumping to terminal & reading the mail database at terminal; then copy it to the mail app & write replies (which was much slower!
) but hopefully you get the point from this example. (when this release was fully upgraded, the mail was no longer ignored
I've shared $HOME between Ubuntu, Debian, Fedora & OpenSuSE, and in my opinion the OS makes no difference; HOWEVER the age of the software stack in the sharing OS makes a huge difference.
Your question relates to different age of stacks; thus this quick example of a single problem. If data matters to you; you'll need to compare the versions of each of those packages/programs to ensure they'll cope correctly when sharing data with a newer/older version of the app; ie. do your homework first. Homework is on a package basis; ie. every app where you value your data.
From a dual boot sharing $HOME, I then moved to loading specific directories onto my $HOME for specific apps, and for some apps keep more than one copy of the data (due to software stack age differences
), and actually had scripts which would keep those different directories in ~sync, as I use more than a single box; but want my files available regardless of which box I'm actually using (Hey I'm using Ubuntu now, but 30 minutes ago I was on a different box running Debian
I stopped sharing $HOME, in time even stopped sharing app directories mounted from a NFS share onto the local $HOME/.. directory.
Now my shared data is just saved on the NFS share & is available on all my devices. It's available for all my OSes, all my boxes (with local network access anyway
), and works regardless of the age of the stack.
I've had other problems too, some were detected quickly; eg. one newer stack detected an older database was being used; so reformatted it matching the newer software stack preference... When I next rebooted and returned to the other older
OS sharing that data; it just refused to start reporting the database was corrupt (it was unable to read the reformatted database used by the newer app
). FYI: This was a different GNOME app & I've had this issue with a number of apps, and I was mostly a GNOME user back 2006-2011 when I shared my $HOME between OSes thus my mention of the GNOME based apps (which will be common for other GTK desktops such as Xfce, MATE, Cinnamon, etc