shutdown on BSD and Linux

[Rahul Siddharthan]

Bill Hacker wrote:
>Rahul Siddharthan wrote:
>> The question came to my mind again when I saw Ubuntu's specification
>> for shutdown in their future versions:
>>    https://wiki.ubuntu.com/Teardown
>>
>> Basically, it says the majority of init scripts needn't be called at
>> shutdown because the processes can just be sent signals and trusted to
>> do the right thing.  However, some controlled shutdowns *do* need to
>> be done.  Why can the BSDs get away with not doing these controlled
>> shutdowns?
>
>Because the *BSD's are complete *Operating Systems* - with a very long history
>of refinement as well as imrovement.

I don't see how that answers the question.

>A *BSD variant is NOT a 'distro'.  It is developed and tested as a whole-cloth
>exercise. Th core components are know in advance, and tested together.

If you include ports/pkgsrc, it IS a "distro".  And decidedly flaky,
at that, compared to most linux distros.  No BSD comes with Apache or
PostgreSQL in the base system, and only NetBSD includes Postfix, to
give the three examples in Ubuntu's teardown wiki article.

>Think of *BSD as the refined 'whole system' characteristic of a Mercedes - auto
>
>or truck.  Linux, by comparison, is any of a brazillion varieties of
>garage-built hot-rod - motorcycle to 'bigfoot' pickup truck - kitted together
>out of whatever bits of kit the 'distro' packagers happens to hold in high
>regard.

I'd have taken that seriously at one time -- in fact I did -- but one
too many crashes that completely trashed my UFS+softupdates filesystem
changed my mind.  When I reported that on FreeBSD, the answer is yeah,
ATA does write-caching and lies about it and sucks generally, tough,
use SCSI.  (And I'm not the only one to have had trashed filesystems,
there are plenty of "unexpected softupdates inconsistency" errors
reported on lists.  Some bugs were found and fixed by Matt, IIRC, but
it looks like only Kirk McKusick really understands softupdates.)

Yes, I use cheap ATA hardware, and don't always notice when my laptop
battery is going to die, and sometimes plug in unstable devices, so I
have occasional crashes and unclean poweroffs.  On Linux ext3, held in
near-universal scorn by BSD types, I have NEVER had a trashed
filesystem, and only ever lost data in a couple of open files (usually
system logs).  In fact, the only problem I ever remember having on
linux is poor VM behaviour, exhibited when a runaway process eats all
available RAM.  And these days that's much better too.


>Distro's aside, Linux' Kernel is nothing to write home about, either, so it is
>starting off handicapped.

It's way better than BSD kernels on modern hardware, that need to
handle devices that may appear or disappear without notice -- USB,
PCMCIA, firewire.... I have NEVER panicked a Linux system by removing
a USB device, no matter whether it was in use or not.  I can panic
FreeBSD or Dragonfly in a few seconds that way.  And if it doesn't
panic immediately, it spews absurd messages about being unable to
detach the device because it is "in use", and then panics half an hour
later.  And, again, I'm not the only person to have seen this.

In fact, I have only ever panicked a Linux system in years by using a
ndiswrapper driver, and that too went away after I recompiled a kernel
with 16K stack space (which Windows has and NDIS drivers assume).  

>But it is free and available, and 'has lots of drivers...' 

. .. and WORKS.

>> BTW - the poweroff on my laptop, with Dragonfly and FreeBSD (last I
>> checked), is also accompanied by a rather alarming and short-lived
>> whine, as if a spinning disk or fan was suddenly stopped.  I don't get
>> this sound with linux or windows.
>>
>> Rahul
>
>Sounds more like a CPU-fan or HDD spun UP, not down, as needed in a burst of
>intensive activity (putting stuff away properly before shutdown..)

Nope... if the burst of activity happens while (as I said) the machine
is powering off, something is seriously amiss.  On linux, the sounds
die away and the machine is silent for a second or two BEFORE poweroff.

Rahul