On Thu, Feb 25, 2010 at 21:49, Aaron Bartell <aaronbartell@xxxxxxxxx> wrote:
ÂI don't know *why* they ask you to reboot. ÂDoes it have
something to do with the registry?
No, it has to do with two things:
First, Windows's locking system is mandatory. If a file is locked, it
can't be replaced or deleted. This is completely different in
Unix-style OS like Linux and Mac OS X. You can delete locked or in-use
files in Linux - the inode will still be around, can still be used by
the programs that already have it open and will be deleted by the
filesystem effectively when the refcount is 0.
Second, updating core system libraries usually requires all programs
using them to be restarted. Windows has a lot of core system
libraries, much moreso then Linux. For example, wininet.dll (HTTP API)
is used by IE, Windows Update, etc. lots of programs. Mandatory
locking requires these files not to be locked - but that's essentially
impossible to achieve as long as the system is running fully - so
these kind of replacements can only be done during the boot process.
On Linux, where there's no mandatory locking and you can replace the
libc while the system is fully running, you have other issues to think
about. Assume a critical bug in the foobar() function in the libc was
fixed. You replace the libc. Apache keeps running. Now, apache was
started with the old libc and still references it. Thus, foobar() is
still vulnerable. You haven't fixed the security issue yet, you'd need
to restart apache to do so. Or if we're talking about interactive use,
you may need to restart the X server. Also, having a different version
of the libc loaded may cause other issues when dynamically loading
libc modules, for example for internationalization.
Now, application level patching (e.G. Exchange, SQL Server, Apache,
MySQL) works the same on both Linux and Windows - they don't require a
reboot. Though you may need a reboot on Windows if a file can't be
replaced due to mandatory locking. SQL Server CU/ServicePacks will
tell you if it can do the install without needing a reboot beforehand.
There are also kernel level patches. These require a reboot on any
platform. There are some exceptions here, for example Linux's kexec,
but none of these are seriously used in production environments.
Do they even need to actually have you
reboot? ÂI don't know, but I do it so I don't have to risk something not
working right after the install/upgrade.
On Vista/2008 and up, you can keep the system running after installing
updates with 100% no ill effects. The servicing stack was completely
overhauled.
On XP and 2003, it usually wasn't an issue either, but the
recommendation was to reboot immediately.
With that said it might be a case of the type of personality Microsoft
entertains (i.e. believe it's acceptable to bring down a server after
installing new software or applying an update).
You phrase this very negatively, but i think Microsoft's approach with
requiring the reboot is just playing it safe. The issues you can get
on Linux when updating the libc without rebooting are NOT funny.
midrange.com
