Wednesday, October 24, 2012

Customizing grub2 boot options in Fedora 18

In days of old, with RedHat Linux, and Fedora and Centos, on servers I used to disable the default behaviour of console display blanking screen-saver by putting the 'setterm -blank 0' command into file '/etc/rc.local'. On recent versions of Fedora, you do not get a '/etc/rc.local' file, however you can create one like this:
# vi /etc/rc.d/rc.local
# chmod a+x /etc/rc.d/rc.local
# ln -s /etc/rc.d/rc.local /etc
# ll /etc/rc.local
lrwxrwxrwx. 1 root root 18 Sep 24 15:44 /etc/rc.local -> /etc/rc.d/rc.local

But this no longer seem to be an appropriate way to run  'setterm -blank 0', as the command just seems to be ignored. I tried setting my '/etc/rc.local' file to this:
# cat /etc/rc.local
/bin/date > /root/rc.local.start
/bin/sleep 5
/bin/setterm -blank 0
/bin/date > /root/rc.local.done

..just to prove the command was executing, and it was, but still the screen blanked after the timeout.

After much Googling, I found the answer was to use a kernel command line option of 'consoleblank=0'.

Now again in days of old, I would just edit '/etc/grub.conf' to set these kernel parameters, But now recent versions of Fedora are using Grub2, things have changed. I found that you can specify the kernel parameters, in file '/etc/default/grub', using the 'GRUB_CMDLINE_LINUX_DEFAULT' option.

And while I was editing the grub file, I decided to change some other settings. I wanted to disable the graphical boot splash screen, and just have a basic 'text' screen to select which kernel to boot, so I added 'GRUB_TERMINAL=console'. I also removed the 'rhgb quiet' options, as I like to see all those boot messages scrolling up the screen.

# cd /etc/default/
# cp grub grub.orig
# vi grub
# diff -u grub.orig grub
--- grub.orig   2012-10-24 10:28:28.120869824 +0100
+++ grub        2012-10-24 10:52:40.940184853 +0100
@@ -1,6 +1,8 @@
 GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
-GRUB_CMDLINE_LINUX=" rd.lvm=0 rd.luks=0 $([ -x /usr/sbin/rhcrashkernel-param ] && /usr/sbin/rhcrashkernel-param || :) rhgb quiet"
+GRUB_CMDLINE_LINUX=" rd.lvm=0 rd.luks=0 $([ -x /usr/sbin/rhcrashkernel-param ] && /usr/sbin/rhcrashkernel-param || :)"
# grub2-mkconfig -o /boot/grub2/grub.cfg
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.6.2-2.fc18.x86_64
Found initrd image: /boot/initramfs-3.6.2-2.fc18.x86_64.img
Found linux image: /boot/vmlinuz-3.6.0-1.fc18.x86_64
Found initrd image: /boot/initramfs-3.6.0-1.fc18.x86_64.img

Ok, so lets check that worked....
# grep $'\tlinux' /boot/grub2/grub.cfg
linux   /vmlinuz-3.6.2-2.fc18.x86_64 root=UUID=9d81334c-ed70-4cc8-9279-e82eb8cdef1e ro rd.lvm=0 rd.luks=0  consoleblank=0
linux   /vmlinuz-3.6.0-1.fc18.x86_64 root=UUID=9d81334c-ed70-4cc8-9279-e82eb8cdef1e ro rd.lvm=0 rd.luks=0  consoleblank=0

In the above, note how I get grep to match for the tab character.


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