Re: Question about /home

[Michael Parson <mparson%bl.org@localhost>]

On 2022-01-22 11:20, Todd Gruhn wrote:
> is /home in the  /  directory?   What happens if  /  is too small?

/home can be it's own partition, it's own disk, or, it can be on the /
fs, all depend on how you set it up.

If a filesystem fills up, then, the first obvious problem is that 
nothing
new can be written.  Depending on which directories are on the 
filesystem,
the consequences vary.

If you have a single filesystem, /, and you fill it up, then you're
not going to get any more logs (/var/log/*), mail won't be delivered
(/var/mail, /var/spool/mqueue), anything that creates tmp files in /tmp
or /var/tmp to function are going to have problems, etc, users logged in
won't be able to do much other than log in and look at things, won't be
able to edit files, download anything, compile programs, etc.

> Can it be moved to /usr?

It can be, as long as you either symlink /usr/home to /home, or fix
everything that looks for home dirs to know to look in /usr/home.
This will mostly be fixing entries in /etc/passwd, but there could be
scripts, config files, etc, that expect a given user's $HOME to be under
/home

> I recall that /home had its own filesystem/sector once upon a time...

Back in the old days, when disks were measured in megabytes, possibly
small numbers of gigabytes, and before we had things like log structured
filesystems, it was good practice to separate stuff that might have
lots of read/writes off the / filesystem so that should something
catastrophic happen (power loss, kernel panic, etc), the potential
corruption to / would be limited and it would most likely pass the
boot-up fsck and you'd have a functional enough system to repair any
other damage that might have been done. So you might have /usr, /var,
and /home on separate partitions or even disks. If you were in a
networked environment, /home might even be an NFS mount from somewhere
else, might even have /usr/local be an NFS mount that has common tools
or programs that might be shared across multiple systems.

In those days, I tended to set up my systems to look something like:

/
/var
/home
/usr
/tmp (tended to be a ramdisk of some sort)

Then, depending on the number of disks I had, if it was a networked
environment with shared resources, etc, I might have separate /usr/local
partition, disk, or network mount, /home might be shared from a central
server, etc.

The other advantage to separate partitions back then was that the unix
tape-backup program dump(8) used to only be able to handle things on the
partition level, so, in order to back up /home separate from the other
stuff, you needed /home to be on a partition of its own. At some point,
at least on NetBSD, dump(8) was adapted to handle things at a directory
level, removing that limitation.

--
Michael Parson
Pflugerville, TX
KF5LGQ