gnu linux update question

[fred smith]

On Tue, Jun 28, 2011 at 11:52:17AM -0430, Patrick O'Callaghan wrote:
> On Tue, 2011-06-28 at 17:14 +0100, Bryn M. Reeves wrote:
> > On 06/28/2011 05:07 PM, Andrew Haley wrote:
> > > On 06/28/2011 04:59 PM, Petrus de Calguarium wrote:
> > >> It is common knowledge that one does not need to reboot for updates to take 
> > >> effect in GNU Linux.
> > >>
> > >> However, in actual practice, this is not so. I could cite many examples, but 
> > >> this should suffice:
> > >>
> > >> On Sunday evening, I installed a new updates-testing version of mesa and then I 
> > >> suspended the machine for the night. The following Monday morning (yesterday), 
> > >> I resumed the machine and suspended it again around noon. I again resumed the 
> > >> machine at about suppertime and _powered_ _it_ _down_ about 2 hours later. An 
> > >> hour or two after that, I powered it back up and the mesa testing update turned 
> > >> out to be bad and I was not able to log in. I did not know which program was at 
> > >> fault, because the bad program had been installed over 24 hours prior, but was 
> > >> only showing itself to be bad after a power off.
> > >>
> > >> Could someone explain how reboots are not needed in Linux for updates to 
> > >> _take_, given the evidence to the contrary.
> > > 
> > > If a process has a file open and that file is replaced with a new copy,
> > > the process is still using the file handle for the old file.  This is
> > > normal UNIX, nothing new.  How could it be otherwise?
> > 
> > Or to put it in simpler terms: when you update a component you need to re-start
> > the application(s) that use that component. When that is a component of the
> > whole desktop environment (like mesa) you will need to log out of your session
> > and log back in again.
> > 
> > For a couple of releases now the graphical updater tools have supported the
> > ability to warn the user when this is the case. If you were using these tools
> > then you should have received such a warning.
> > 
> > Note that suspending and resuming does not count here since you are simply
> > suspending the running (old) copy and then resuming it with open files and other
> > state intact.
> 
> After updating, I always run needs-restarting to see what running
> processes are affected. I'm surprised more people don't seem to know
> about this program.

wow! I never heard of that one before. I'll certainly be checking it out.

thanks, Patrick!

> 
> BTW it's a Python script of only a couple of pages in length. Figuring
> out how it works is a good exercise in understanding Linux (not to
> mention Python :-)
> 
> poc

-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
                       I can do all things through Christ 
                              who strengthens me.
------------------------------ Philippians 4:13 -------------------------------