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List:       macports-users
Subject:    Re: migration hickup
From:       Ryan Schmidt <ryandesign () macports ! org>
Date:       2021-03-10 18:34:12
Message-ID: A45EB90A-00D6-4B79-A1A7-8C5B9D1B62DD () macports ! org
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On Mar 10, 2021, at 05:26, joerg van den hoff wrote:

> On 09.03.21 18:41, Ryan Schmidt wrote:
> > On Mar 9, 2021, at 11:34, joerg van den hoff wrote:
> > > so I find this strange: seemingly everything is just fine (macports user and \
> > > its home dir exists etc.) but I get that "cannot change owner: no macports \
> > > user" warning nonetheless. so this looks like OSX had not a consistent view of \
> > > the state of affairs across different utilities at that point? notably `dscl' \
> > > knowing that user is not sufficient? what, then, is the reliable/correct way to \
> > > decide whether a user account "really" exists? but whatever ...
> > I'm sorry, I don't know and I can't completely explain what you've observed.
> > > understood. will try to recall the procedure in due time when doing another \
> > > migration to a new machine...
> > No need to recall anything since it's documented in \
> > https://trac.macports.org/wiki/Migration. That document is geared toward \
> > migrating from one OS version or architecture to another, but it could be \
> > enhanced to address the case of migrating from one machine to another while \
> > keeping the same OS version and architecture. If you'd like to make those \
> > enhancements feel free; anyone can edit the wiki.
> 
> well, I might try that. at least it seems not true that for said type of migration \
> (same OS/arch) one needs to first nuke the macports installation. from the current \
> migration page: "Note: If you move from one Mac to another Mac using ​Migration \
> Assistant, you have to do it ["it" meaning uninstall MacPorts] first."

That sentence is meant to be taken in context of the rest of the page, which is \
currently all about the need to reinstall MacPorts and ports when migrating from one \
OS version or arch to another.

If you're moving from one Mac to another where both have the same OS version and \
arch, then you don't need to do anything to fix MacPorts; your existing MacPorts \
installation will work just fine if you copy everything correctly. For example, using \
a cloning utility like Carbon Copy Cloner copies everything correctly.

Migration Assistant does not copy everything correctly. It does not preserve the \
correct home directory location of the macports user nor of any of the user accounts \
that MacPorts ports might create. So if you use Migration Assistant, then you will \
have to take additional steps afterward. Either you have to exclude those accounts \
from migration and recreate them afterward, or if you did not exclude the user \
accounts then you have to fix their home directories afterward. 


> OTOH I am not quite sure _what_ to recommend: my "strategy" was
> 
> 1. migrate everything offered by Migration Assistant _except_ the macports user's \
> account. 
> 2. reinstall MacPorts from dmg image
> 
> so I could write something to that extent into the wiki if it helps...
> 
> but I am not at all sure what would have happened if I had done it the way you \
> suspect to be better:

You misread me. I agreed with you that *not* migrating the macports user was the \
easiest way to do it, provided that you recreate the user later by re-running the \
MacPorts installer.

If you instead *did* migrate the macports user, then Migration Assistant will have \
messed it up and it would need to be fixed.


> 1. migrate everything offered by Migration Assistant _including_ the macports \
> user's account (whose home dir than is moved apparently to /Users in the process) 
> 2. mv macport home dir back into the /opt/local tree
> 
> open questions would be: how exactly? with what permissions? does that really yield \
> a working MacPorts installation or would the same warning result I have seen ("no \
> macports user") and which necessitated reinstall of MacPorts from the dmg image?


If you tell Migration Assistant to migrate a user account, it will migrate the user \
account. That means the user account and its home directory will exist on the new \
system. Migration Assistant will relocate the user's home directory into /Users, \
which is inappropriate for the macports user and all of the user accounts that ports \
might create, therefore you will need to undo those changes manually later. To do \
that, for each affected user account, you need to:

1. mv the home directory from /Users/whatever to where it was supposed to be, and
2. use the dscl command to fix the user's NSHomeDirectory entry to match where the \
home directory now is.

For the macports user this is easy enough since we know that its home directory is \
/opt/local/var/macports/home. But for all of the other user accounts, you would need \
to read that port's Portfile to figure out where its home directory is supposed to \
be.

If you tell Migration Assistant *not* to migrate a user account, it will not migrate \
the user account. That means the user account will not exist on the new system. I am \
not certain whether the user's home directory would be copied. It seems like it \
should not be, but I can't test it right now.


I think it would be a good idea if the migration wiki page specifically mentioned \
this problem of the Migration Assistant. I would probably have the page recommend not \
to migrate MacPorts-related user accounts and instead recreate them after migration. \
To recreate the macports user, re-run the MacPorts installer. To recreate users and \
home directories created by any port, reinstall that port (sudo port -n upgrade \
--force portname). Users might want to look into the home directories of each \
MacPorts-created user before migration to make sure there's nothing important in \
there in case it does not get copied.

Many users will not be aware of the problem until after migration is complete, so we \
should also describe how to recover from a migration where the user accounts were \
migrated and relocated.


`port diagnose` should probably be modified so that it detects any home directories \
that were misrelocated to /Users and warns the user about it, perhaps referring them \
to the future version of the Migration page for help in fixing it.


Maybe an even nicer idea: Whenever MacPorts creates a user account, it could record \
its home directory in a new table in the registry. `port diagnose` could check if any \
home directory doesn't match what we recorded and offer a way to set it back. Or this \
could become part of the unfinished `port migrate` command \
(https://trac.macports.org/ticket/56019) (or maybe it already includes this; I don't \
know).


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