Mikael Bak <mikael@t-online.hu> writes:
> I would like to do a binary upgrade from 7.1 to 7.2. I've seen the
> instructions here:
> http://www.freebsd.org/releases/7.2R/announce.html
>
> I've heard that it's safest to start the machine in single user
mode
> when doing upgrades, but I see no notice about it in the announcement.
The announcement explicitly points to the FreeBSD Handbook for the
procedure for doing source upgrades, which does indeed including booting
the new kernel into single-user mode before doing the installworld.
> So my question is: Is it ok to do this binary upgrade without start
> single user mode first?
Sure. It's riskier; if the new kernel doesn't boot, but you already
have the new userland installed, you're stuck. You'll need to recover
from some other bootable media, which may well take quite a while.
Just how risky it is depends on how big a version jump you're making.
> If no, must I reboot my machine to enter single user mode?
Rebooting is at least as important as getting into single-user mode.
You want to know your kernel is good. Single-user mode is good, too,
because you don't want to change utilities out from under running
processes if you can help it.
All of that said, though, I do it all the time on lightly loaded
machines. I always reboot after completing the upgrade, and usually
also in between the installkernel and installworld. Trying the upgrade
on a test machine first helps reduce the risk as well.
Unfortunately, machines that you want to avoid downtime on are usually
the same ones that you really can't afford to fail an upgrade...