Re: git: 36db6b04962a - main - hier(7): document /home/ and /usr/home/

On 11 May 2023, at 9:58, Rodney W. Grimes wrote:

>> On Wed, 10 May 2023 16:48:12 -0500
>> Mike Karels <mike@karels.net> wrote:
>>
>>> On 10 May 2023, at 10:13, Cy Schubert wrote:
>>>
>>>> In message <ba22a75d-06c0-371e-603e-7ded9d1dca97@freebsd.org>, Mitchell
>>>> Horne w
>>>> rites:
>>>>> On 5/10/23 11:19, Rodney W. Grimes wrote:
>>>>>>> The branch main has been updated by mhorne:
>>>>>>>
>>>>>>> URL: https://cgit.FreeBSD.org/src/commit/?id=36db6b04962a01ff7b21592def02d
>>>>> 4c570dac939
>>>>>>>
>>>>>>> commit 36db6b04962a01ff7b21592def02d4c570dac939
>>>>>>> Author:     Mitchell Horne <mhorne@FreeBSD.org>
>>>>>>> AuthorDate: 2023-05-10 12:53:56 +0000
>>>>>>> Commit:     Mitchell Horne <mhorne@FreeBSD.org>
>>>>>>> CommitDate: 2023-05-10 13:25:17 +0000
>>>>>>>
>>>>>>>      hier(7): document /home/ and /usr/home/
>>>>>>>
>>>>>>>      Reviewed by:    imp
>>>>>>>      MFC after:      1 week
>>>>>>>      Sponsored by:   The FreeBSD Foundation
>>>>>>>      Differential Revision:  https://reviews.freebsd.org/D40002
>>>>>>> ---
>>>>>>>   share/man/man7/hier.7 | 10 ++++++++++
>>>>>>>   1 file changed, 10 insertions(+)
>>>>>>>
>>>>>>> diff --git a/share/man/man7/hier.7 b/share/man/man7/hier.7
>>>>>>> index ff11289436a1..b6759dd6e65b 100644
>>>>>>> --- a/share/man/man7/hier.7
>>>>>>> +++ b/share/man/man7/hier.7
>>>>>>> @@ -90,6 +90,10 @@ file descriptor files;
>>>>>>>   see
>>>>>>>   .Xr \&fd 4
>>>>>>>   .El
>>>>>>> +.It Pa /home/
>>>>>>> +user HOME directories.
>>>>>>> +This is a symlink to
>>>>>>> +.Pa /usr/home/
>>>>>>
>>>>>> /usr is "contains the majority of user utilities and applications"
>>>>>> it should not contain home directories.
>>>>>>> I do not know when this move to usr came about it was traditionally
>>>>> /home.
>>>>>> I do not know why /usr/home even exists, it is not needed by
>>>>>> anything I am aware of.  If we have a compatible link it
>>>>>> should be, usr/home -> ../home and /home should be the
>>>>>> directory.
>>>>>>
>>>>>
>>>>> I agree that /usr/home is strange, and is unique (?) to FreeBSD.
>>>>>
>>>>> The oldest commit in the output of `git log --grep '/usr/home'` is:
>>>>>
>>>>> commit f2400d465896a8e4f6fdc57eba840cf49b25bbbd
>>>>> Author: David Nugent <davidn@FreeBSD.org>
>>>>> Date:   Fri Jan 3 04:42:18 1997 +0000
>>>>>
>>>>>      Implemented /home -> /usr/home symlink kludge.
>>>>>      If home basedir would be created in the root partition, create
>>>>>      it under /usr instead, and symlink /basedir -> /usr/basedir.
>>>>>
>>>>> Notes:
>>>>>      svn path=/head/; revision=21242
>>>>>
>>>>>
>>>>> So it has been this way for 26 years at least. I do not know what to say
>>>>> about whether /usr "should" contain it, but it does.
>>>>
>>>> Usually history matters. I can understand not changing it. On the flip
>>>> side, I cut my UNIX teeth on SunOS 4 and Solaris where /home was /home --
>>>> albeit automounted from /export/home on localhost or some NFS server. In
>>>> the Red Hat land at $JOB, /home is its own partition (actually an LVM
>>>> volume). In both cases /home is not in /usr because end-users can fill
>>>> /usr. This can be problematic operationally because it's yet another
>>>> headache to deal with should someone fill the filesystem. Filling /usr is
>>>> more serious than filling /home.
>>>>
>>>> As a point of interest, when I installed my first FreeBSD many moons ago I
>>>> used the Solaris standard of /export/home, using amd (now automount) to
>>>> serve my /home. I'm not advocating we do this, it's overkill, but /home
>>>> should not live in /usr. It's a potential headache for any sysadmin.
>>>>
>>>> With ZFS the solution is easy. With UFS based systems there are a lot of
>>>> other factors that go into how we install the "default" from the get-go.
>>>
>
> First off, thank you Mike for looking at this closer.  Add me to any reviews
> you might creat.
>
>>> The situation is a fair mess.  It took me a little while to figure out that
>>> the kludge referenced above is in the pw(8) command, which is used as the
>>> backend to adduser(8).  Neither /home nor /usr/home is in the base package.
>>> adduser defaults to /home/user, and creates the parent directory (e.g. /home)
>>> if it does not exist, but if there is no internal slash, pw moves the parent
>>> to /usr.  In this case, it makes the symlink from  root.  zfs is different,
>>> in that it includes a usr/home dataset already (created by bsdinstall).
>>> In this case, creating a user with /home/user causes the symlink to be added
>>> as a side effect.
>>>
>>> I?m sure the kludge was originally done when root and /usr were separate
>>> file systems by default, root was small, and there was no /home by default.
>>> However, we now default to a single large file system (with datasets, in
>>> the zfs case).
>>>
>>> All of this really is a horrible kludge, and it is a house of cards.  I'm
>>> amazed that it doesn't break more often.  I'm tempted to remove the kludge
>>> and change the zfs setup to create a home dataset rather than usr/home.
>
> Or make it a menu option(s):
> if (zfs) "Create a user home dataset?" (default yes)
> if (ufs) "Create a user home directory?" (default yes)

Are you suggesting that bsdinstall should do this?  For ufs, there is no
need.

> 	"User home location: /home" (This is default)

Are you proposing that the default for pw should be set at this point?
That doesn’t seem necessary, and I don’t know if it would work from
bsdinstall.

> As far as I am concerned the symlink can just die....

I agree, but that requires a change to pw.  It creates the symlink on the
first account creation using /home.

>>> However, if zfs users explicitly configure a home directory under /usr/home,
>>> this would end up in the usr dataset.  An alternative would be to remove the
>>> code from pw to create the parent directory entirely (which seems sensible),
>>> and create a /home directory for ufs installs.  I don't know how well known
>>> it is that adduser/pw will create parent directories for home directories
>>> though.  This cleanup would change the default location for home directories
>>> to /home, which makes more sense.  It would require documentation, e.g. in
>>> the release notes.  The changes would only affect new installations, not
>>> upgrades.
>>>
>>> Thoughts?
>>>
>>
>> Adding home would require a change to BSD.root.dist, since it's not
>> currently in there.  Only usr is present.
>
> It should *not* be in the etc/mtree/BSD.*.dist files at all.
> And it is not on my 13.1R system.  It would not need to be
> in BSD.root.dist either, this is a *post distribution* created
> directory/dataset.

I’m curious why you think this.  But if pw retains the ability to create
the parent directory for the user directory (and I now think it should),
there is no need for a /home by default.

>> IMHO changing pw would be a reasonable approach.
>
> I am mixed on this.... it more or less does the right
> thing, and if a user specifies /tmp/foolishidea/home/$USER
> that is on them.   No one said all users homes must be
> in the same location.

Except for moving parent directories with a single component under /usr,
and creating a symlink for them...

My current plan is to change pw not to move things under /usr, change the
zfs setup to use a home dataset rather than usr/home (corresponding to the
pw default), and then change the various man pages that refer to /usr/home.
Does that seem reasonable?

		Mike