Change GRUB boot options without menu.lst

willroberts · 09-26-2011, 09:03 AM

I've recently switched to Debian for home use after using CentOS almost exclusively over the past few years. To edit the startup menu entries in Grub, I usually just edited menu.lst directly.

In a new Debian 6 install, menu.lst does not exist, and grub.cfg is generated automatically by update-grub. I looked through /etc/default/grub and /etc/grub.d to see if the menu options were present, but didn't find any.

What I want to do is add a 'vga=###' option to the kernel parameters. How can I do this using update-grub?

amani · 09-26-2011, 10:52 AM

grub.cfg can be edited

vga=... can be added to kernel line

Larry Webb · 09-26-2011, 11:18 AM

Quote:

Originally Posted by amani

grub.cfg can be edited

vga=... can be added to kernel line

The only problem would be later if an update-grub gets run it will go back to the default.

willroberts · 09-26-2011, 12:19 PM

Quote:

Originally Posted by Larry Webb

The only problem would be later if an update-grub gets run it will go back to the default.

Right. The header of grub.cfg says "DO NOT EDIT THIS FILE", so I would like to learn the correct way to do this.

One solution someone recommended at work was to edit /etc/grub.d/10_linux and edit this section:

Code:

while [ "x$list" != "x" ] ; do
  linux=`version_find_latest $list`
  echo "Found linux image: $linux" >&2
  basename=`basename $linux`
  dirname=`dirname $linux`
  rel_dirname=`make_system_path_relative_to_its_root $dirname`
  version=`echo $basename | sed -e "s,^[^0-9]*-,,g"`
  alt_version=`echo $version | sed -e "s,\.old$,,g"`
  linux_root_device_thisversion="${LINUX_ROOT_DEVICE}"

Making this change:

Code:

linux=`version_find_latest $list vga=###`

This would make any kernel detected by grub use the specified video mode after running update-grub.

Is there any more proper way to do this?

Larry Webb · 09-26-2011, 01:59 PM

Being honest I have never tried to edit the vga mode. Here is the tutorial I use when trying to install or alter grub. It is from ubuntu but the rules should apply here also except you will have to use su - inplace of sudo for root permission.

grub2

I will have a spare moment this evening and will see if I can find more for you or try myself.

syg00 · 09-26-2011, 06:51 PM

Me too - that's a good article.
Additions to /etc/default/grub should be the answer. GRUB_CMDLINE_LINUX and GRUB_CMDLINE_LINUX_DEFAULT are standard (supported) entries.

willroberts · 09-26-2011, 11:09 PM

Thanks for the help! That's exactly what I needed.

Here were my changes to /etc/default/grub:

Code:

GRUB_CMDLINE_LINUX=""
GRUB_CMDLINE_LINUX_DEFAULT="" (removed 'quiet')
GRUB_GFXMODE=1024x768

Then update-grub && reboot and everything is perfect!

Edit: I jumped the gun, GRUB_GFXMODE is only for the boot menu itself. I'm trying to find a way to set the console resolution (the resolution used after the OS has loaded).

syg00 · 09-26-2011, 11:55 PM

Oops - I think support for things like vga= and video= all went away with KMS. Meaning, of course, that this isn't really a grub issue at all.

You could try adding it to the either of those lines, but "it's your gun, and your foot".

Larry Webb · 09-27-2011, 05:55 AM

The safe way to test this is to install another grub to a separate partition and then chainload the version you want to run the test on with a direct boot to the distro. If set freezes or something bad goes wrong delete the added grub or correct it and you are back in business. I did not have the time last night to try this.

(Yes I have to use wife,s set at night and she did not work last night.)

colorpurple21859 · 09-27-2011, 08:15 AM

I think "video=1024x768" will work, I use "video=800x600" in slackware-current to change the console front size

Larry Webb · 09-27-2011, 12:09 PM

Quote:

Originally Posted by colorpurple21859

I think "video=1024x768" will work, I use "video=800x600" in slackware-current to change the console front size

Right but you are probably using grub legacy. Grub2 has no provisions that I have seen.

TobiSGD · 09-27-2011, 12:21 PM

Quote:

Originally Posted by Larry Webb

Right but you are probably using grub legacy. Grub2 has no provisions that I have seen.

Isn't that a kernel parameter (and should therefore be independent of the bootloader)? By the way, the default bootloader in Slackware is LILO.

colorpurple21859 · 09-27-2011, 12:58 PM

According to Ubuntus Grub2 tutorial this is where in /etc/default/grub that kernel paramters are enter.
#

GRUB_CMDLINE_LINUX

* Entries on this line are added to the end of the 'linux' command line (GRUB legacy's "kernel" line) for both normal and recovery modes. It is used to pass options to the kernel.
or
you could create a custom entry and and enter the kernel paramter there.

I know Slackware uses lilo, but on my system at home I chainload Slackware from ubuntu as well as having lilo install on the Slackware partition.