When you emerged grub-0.97-r5, this was displayed on your console: WARN: postinst *** IMPORTANT NOTE: you must run grub and install the new version's stage1 to your MBR. Until you do, stage1 and stage2 will still be the old version, but later stages will be the new version, which could cause problems such as an unbootable system.
Yes, the ebuild writes that to the screen.But silently, in the background (because every output is piped to /dev/null - how evil!), the ebuild calls grub with some commands inside your grub.conf.
If there's a setup-command in your grub.conf, it is indeed executed. So if that command is outdated (something you won't notice, since that command is not used by grub in any situation i know), the ebuild will execute that setup-command and write to some device's boot sector. How evil, again!
Regards, Sven P.S.: here's the code from grub-0.97-r5.ebuild: if [[ -e ${dir}/grub.conf ]] ; then egrep \-v '^[[:space:]]*(#|$|default|fallback|initrd|password|splashimage|timeout|title)' \
"${dir}"/grub.conf | \ /sbin/grub --batch \ --device-map="${dir}"/device.map \ > /dev/null fi
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