[mythtv-users] mythfilldatabase failing after OS upgrade

[Daryl McDonald]

On Fri, Jan 6, 2023 at 6:09 PM Mike Perkins <mikep at randomtraveller.org.uk>
wrote:

> On 06/01/2023 21:01, Hika van den Hoven wrote:
> > Hoi Daryl,
> >
> > There is one thing you always have to remember when you move data like
> > this between old and new systems or even more important, share them
> > between two installation on one physical system.
> >
> > usernames and groupnames are meaningless to the computer. The computer
> > uses the numerical u(ser)id and g(roup)id. For our benefit as stupid
> > mortals it translates it to a name.
> >
> > However the translation between the numerical id's and the names is
> > unique to every installation, with the only exception of root. Root
> > always has a uid of 0 and a gid of 0. Some of the groups have
> > generally by agreement the same gid, but they could be another.
> >
> > So if you create a new installation and want to copy or share data
> > with an old installation you have to ensure the involved users and
> > groups have the same uid and gid on both installations. You can set
> > the uid on user creation (if not already taken by another user).
> >
> > This is why I use ldap for network wide user and group management. The
> > user hika and mythtv have the same uid on all computers and most
> > groups likewise.
> >
> I would add another complication, which I discovered copying a disk from
> an old backend to a new one
> (duff motherboard). Many of the users and groups generated by a fresh
> install are "system" users;
> that means they are usually used only by OS subsystems. These are less
> than 1000 and typically
> assigned the next available numbers. As the order of installation is
> indeterminate during an OS
> install, these are essentially random and won't match the UIDs and GIDs on
> any other host.
>
> Mythtv as installed from repos is often treated as a "system" install,
> meaning that the UID and GID
> the user "mythtv" is assigned can often collide with UIDs from other
> subsystems like, for example,
> gdm and lxd.
>
> For this reason I now *always* create a mythtv user with a known UID and
> GID in the normal user
> range (> 1000) before installing any software. That ensures (i) there are
> no collisions, (ii) any
> existing video files still have the right UID and GID, (iii) the user is
> created under /home rather
> than under /var, and (iv) if I access those directories from elsewhere I
> get sensible answers from NFS.
>
> --
>
> Mike Perkins
>
So, in my case, with a clean install of 22.04/32 on a separate partition of
the 120GB OS ssd and a database restore from 20.04/31 there are bound to be
these kinds of issues? Unless I'm one in one thousand lucky, ouch.

>
>
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