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

Rod and I discussed this, and I’m top-posting a summary of a proposal that
we both support.  I’ll leave the last message from the list below for
reference.  Our consensus is that the main problem is the code in pw(8)
(used by adduser, and hence bsdinstall) that interprets /home as /usr/home,
installing a symlink for /home, and similarly for any other home directory
whose parent has a single component.  We propose to remove that code, and
also modify bsdinstall’s zfs script to create a home dataset rather than
usr/home.  adduser presents a default home directory using /home, so this
will continue to agree.  As Rod said at the start of this thread, home
directories really don’t belong in /usr, and the only reason they were
there is because of the previous root + /usr partitioning.  Now the default
is one large partition.  Of course, people who want to partition differently
can do whatever they want.

It will still be possible for admins to create home directories in
/usr/home, they will just have to do so explicitly for pw to create the
directory, and manually create a /home symlink if desired.  If they have
a small root file system, they will want to put home directories elsewhere.

A followup change would be to change various man pages that refer to
/usr/home.

		Mike

On 11 May 2023, at 12:32, Rodney W. Grimes wrote:

>> 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).
>
> I am proposing we fix this.  More below.
>
>>>>> 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.
>
> Yes I am suggesting that bsdinstall should have a knob to turn
> on (by default) and off the creation of a "home dataset/directory"
> as you well need that if you choose to add users during a bsdinstall
> run, or you may not want a /home at all (currently not possible) as you
> have other mechanisms for dealing with it.
>
> The need for this is just as valid for ufs as it is for zfs.
>
>>
>>> 	"User home location: /home" (This is default)
>>
>> Are you proposing that the default for pw should be set at this point?
>> From all I read the default for pw is already, and should remain /home.
> Man page bears that out.  It has no mention of any symlink or usr/home.
>
>> That doesn?t seem necessary, and I don?t know if it would work from
>> bsdinstall.
>
> No, this has nothing to do with pw directly, this is simply the path
> of the dataset(zfs)/directory(ufs) that bsdinstall should create IFF
> you sayd yes to the create question.  At present this is hardcoded
> into bsdinstall as:
> 	/usr/home
> 	/home -> /usr/home
>
> I am advocating that this should all be controllable from menu.
>
>>
>>> 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.
>
> I am missing something here, pw creates the symlink yuk.
> As far as I was aware the only think that created a symlink
> /home -> /usr/home was bsdinstall.
>
>>
>>>>> 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.
>
> Because there is no need for /home in a base distribution until
> you add a user, and that is a site specific change.  What in
> the base system *needs* /home?
>
>>>> 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?
>
> Yes, then the knobs can easily be added, or scripted install should just
> work to effect the knobs.
>
>> 		Mike
>
> -- 
> Rod Grimes                                                 rgrimes@freebsd.org