[mythtv-users] mythfilldatabase failing after OS upgrade

[Hika van den Hoven]

Hoi Daryl,

Saturday, January 7, 2023, 12:18:00 AM, you wrote:




> 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. 
>  
>  
Yes, and the smartest move would be to start over your 22.04 install
and this time create the mythtv and daryl user as the first thing
after you created the basic install and before you install any other
software and with the same uid as on your 20.04 install.
If you haven't copied over much you can try to repair, but chances are
you either fix to much or to little and stumble into it again in 6
months or so.

I don't have the commands ready at hand as I rarely use them, but I
can look it up.


Tot mails,
  Hika                            mailto:hikavdh at gmail.com

"Zonder hoop kun je niet leven
Zonder leven is er geen hoop
Het eeuwige dilemma
Zeker als je hoop moet vernietigen om te kunnen overleven!"

De lerende Mens