[ale] kernel upgrade newbie

[Jeff Hubbs]

One thing I just remembered about doing kernel compiles:  in many
distros (Red Hat and derivatives in particular), in /usr/src there will
be a symlink called simply "linux" that points to the active kernel
source tree, which will also be in that same directory.  If you move
another kernel tarball into /usr/src and tar -zxf it, it will write into
./linux.  I did this just the other day and in that case, it seemed to
have eliminated the symlink and untarred the new tree into its place. 
Problem was, this eliminated the previous symlinkage and I had to derive
from lilo.conf what the "linux" symlink pointed to (there was more than
one tree present at the time).  

I've read a recommendation to either temporarily remove the symlink or
do your untarring elsewhere, moving the resulting tree to /usr/src.

The trees under /usr/src have no active role in the boot process; the
completed kernels are typically moved to /boot and are referred to by
LILO or GRUB in that location.

Another thing that I have done is to pick a good -j parameter for make. 
>From the man page:

 [-j] Specifies  the  number  of  jobs  (commands) to run
 simultaneously.  If there is more than one -j option, the 
 last one is effective.  If the -j option is given without 
 an argument, make will not limit the number of jobs that 
 can run simultaneously.

The objective is to pick a -j param such that you fill up your machine's
available RAM without making it go into swap. On a 96MB machine running
Mandrake 8.2 with KDE active, I found that 4 was the most I could do and
stay in that regime (I tried 16 and the machine practically bled all
over the floor).  Machine in question was a dual P/133 and a -j of 4
made very good use of both CPUs while keeping the RAM consumption from
getting too high.

Heeding the man page, the use of -j with NO PARAMETER is a path to a
certain kind of hell.  If your machine is solid, it will survive, but
you can pretty much forget doing anything else with it until it's
finished.  I suppose that if you were making a Mosix cluster for
purposes of creating a compile farm, you'd go ahead and do this.  

- Jeff



On Mon, 2002-07-15 at 22:11, Geoffrey wrote:
> Cade Thacker wrote:
> > Hi all,
> > I am feeling rather brave tonight and I am going to try and upgrade my
> > kernel. I am currently running RH7.2 2.4.7-10 and would like to upgrade to
> > 2.4.16+.
> > 
> > As stated in the subject, I have never upgrade a kernel so I have dug
> > around but I have not found exactly what I am looking for. RH has an RPM
> > for 2.4.18 but they say it is for 7.3. Can I use that? Can I just go and
> > download the kernel from kernel.org or should I use the rpm?
> 
> I've done many a kernel upgrade, I always pull the source down and 
> compile it.  It may take you hours the first time, 'cause there's a 
> bunch of options.  You'll be the better for it as you'll learn a lot 
> more about the various kernel settings as well as what is supported.
> 
> I've done this on SuSE, Slackware, Mandrake and Red Hat.  I've also 
> compiled my kernel for my firewall machines on my main machine and moved 
> it over, that way you don't need a compiler and all that space on those 
> machines.  Plus it compiles a lot faster on a PIII 650 then a P75. :)
> 
> > 
> > ANY direction is helpful. I am definitly in water over my head(but still
> > having a blast!)
> 
> A couple of recommendations.  Keep your existing kernel so you can go 
> back to it if you have problems with the new one booting.  It's also be 
> a good idea to have your boot floppy handy you created during the 
> install.  You do have it don't you? :)
> 
> Use lilo or another boot loader so you can select from multiple kernels 
> for testing purposes.  I just recently trimmed mine back, it had 7 
> different kernels to boot from. :)
> 
> I've fallen in love with make xconfig.  It's a very slick menu driven 
> gui for building your kernel.  You'll need X running to use it but it's 
> really nice.
> 
> make menuconfig is the next best solution if you don't want to compile 
> from X.  If you've got an old kernel config from a previous compile, use 
> make oldconfig.
> 
> Have fun and keep us informed. :)
> 
> We really need to have that install fest folks.
> 
> -- 
> Until later: Geoffrey		esoteric at 3times25.net
> 
> I didn't have to buy my radio from a specific company to listen
> to FM, why doesn't that apply to the Internet (anymore...)?
> 
> 
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