Re: Changing the home directory

Hi Tomas,

Tomas Rippl wrote on Tue, Jan 28, 2025 at 10:52:27AM +0100:
> Ingo Schwarze wrote:

>> Why would you do something like that?
>> Not sure whether is dangerous, but it doesn't feel useful either.
>> I never heard of anybody doing something like that.

> This is just part of my effort to learn UNIX.

Oh, i see. Yes, experimentation can be useful for learning,
as long as you are not doing it on a production machine.

> I read that the user's home directory is determined by the settings
> in /etc/passwd in the book UNIX made easy, so I wanted to try it out.

I haven't heard about that particular book, but that doesn't inspire
confidence in it. Yes, in the 1970ies, it did work like that, but the
master.passwd(5) file format first appeared in 4.3BSD-Reno on 1986, so
your book might either be almost 40 years out of date, or it's dumbing
things down so much that they become outright incorrect.

While master.passwd(5) is a typical BSD thing and other systems
user other methods for similar purposes (for example, you might
have heard about "shadow password" files), i doubt that may systems
are still in use where directly editing /etc/passwd is still enough.

Consequently, when reading that book, make sure to have an ample
supply of salt at hand (at least as much as a moose would be willing
to consume on a fine spring day).

>>  $ man master.passwd pwd_mkdb vipw

> Thank you! I have looked through the manual pages and understand that
> the key is the contents of /etc/master.passwd, which (ideally using
> vipw) checks the modifications made and regenerates (using pwd_mkdb)
> the contents of /etc/passwd.
>
> Now the new home directory setup for user2 is working! So /etc/passwd
> is apparently only readable by the "public", the operating system
> actually works with /etc/master.passwd - thanks a lot for the
> directions!!

>> Editing automatically generated files rarely ends well.

> I will remember that and limit my playing accordingly.

In principle, reading books and comparing to manual pages to see
whether what they say is still correct, plus a bit of experimentation,
is not a bad way to learn. For advanced users, reading source code
is also recommended.

Have fun!
Ingo