[TriLUG] CentOS 5.5: kickstart shmall and shmmax woes

Brian Weaver cmdrclueless at gmail.com
Thu Jan 6 18:16:12 EST 2011

Well I've run into an issue that kind of has me shaking my head. I'm wondering if anyone on the list might have some idea what is causing the odd behavior that I'm seeing.

The problem I'm running into has to do with a new kickstart install of a CentOS 5.5 system with additional custom packages. We have a build process that replicates the ISO layout so that we can build an installable DVD. As part of the process we build two sets of kickstart configuration files. One for the ISO and one for a network install via HTTP. The kickstart configuration files are built from an identical master source with just the URL being changed. Using the 'diff' command I can verify that the only difference between the two configuration files is that one has 'url --url ....' and the other has 'cdrom' as the installation source.

One of the software packages installed is PostgreSQL version 8.4 that is in the distribution. Our code later creates a database during the %post section of the kickstart file. The problem I'm having is that PostgreSQL is not starting during the network install but is working fine during the cdrom install. The problem is the values 'kernel.shmmax' and 'kernel.shmall' 

The default shared memory size is too small on the network installation but is sufficiently large enough on the cdrom installation. The two installation use the same kickstart file (except installation source), vmlinuz, and initrd.img. To further complicate matters I accessed the shell when the installation starts via ALT-F2 and initially the values for shmmax and shmall are *identical* when the system starts installing packages. At some point during the installation the values for shmmax and shmall change on the cdrom install but do not on the network install. 

The two system install exactly the same RPMs, have the same partition layout, and have been tested on the same hardware. I checked each rpm in the i386/CentOS directory of the DVD using 'rpm -q --triggers --scripts -p $rpm' to see if any of them changed the values of shmmax or shmall. I couldn't find any scripts that modified the kernel values.

I hope I managed to explain it well enough for all to understand the problem. If you have any ideas I'd like to know.


-- Weave

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