Possible to get a variable from Grub2?

[Jose Catre-Vandis]

Have setup a system (one linux OS) that can either be a command line or gui experience and would like to be able to select which version to run at the grub2 menu.

I have carried out a command line installation of Xubuntu 10.04 then added openbox. I use SLiM (Simple Login Manager), which has an entry in rc.local to run it.

Xubuntu offers no way of booting to the cli - that I can find, and SLiM seems to offer no way of turning it off.

So is there any way a bash script could pick up which menu entry in grub2 was selected to be run, to then select whether SLiM should be run or not? I am thinking if I have custom / bespoke menu entries then these would be easier to find.

Example script (in English!) to put in rc.local:

!#/bin/bash

menu=Collect name of grub2 entry selected  << how to do this bit?

if $menu = SLiM then

/usr/bin/slim

endif

done

Or is there a better way?

( no, the "text" kernel option doesn't work with SLiM)
( I can't find a way to start up with runlevel 1 without invoking recovery mode or dropping to a root shell)

Happy to try just about anything (apart from working with animals or children) to solve this!

Thanks

[amauk]

Easiest way is to make menu items that boot to different runlevels

You can specify which runlevel to boot into by appending the number to the end of the kernel line in grub
Eg.

linux /boot/vmlinuz-2.6.38-8-generic.....quiet splash 3

Ubuntu defaults (I think) to runlevel 2
so runlevel 3 can be your CLI only option

You'll need to read up on how to create sysV init scripts, and how to specify which runlevels the script will execute under
Then make an init script for your graphical login manager, and bind it to runlevel 2 only

[Jose Catre-Vandis]

Thanks amauk

SLiM shows up on runlevel 3 as well.

I'll go away and have a read up on sysV init scripts

EDIT

Hang on you've given me an idea.

who -r

tells me which runlevel I am on so if I can check this in my script I can do this?

[dwhitney67]

Ubuntu defaults (I think) to runlevel 2

Are you sure? I always thought that it was runlevel 5.

[ajgreeny]

Are you sure? I always thought that it was runlevel 5.

No it is runlevel 2! Try the

who -r

command.

[amauk]

Hang on you've given me an idea.

who -r

tells me which runlevel I am on so if I can check this in my script I can do this?

Yes,
but I'd advise against rolling your own custom solution

I'd personally stick with init scripts,
mainly because they're standardised and there's an entire framework behind their operation

Say you're in CLI mode, and wish to switch to GUI
How do you do this, with confidence that everything is loaded and working as it should?

On switching runlevels
- All the 'stop' init scripts for the current runlevel get executed and all loaded services stop
- Runlevel changes
- All the 'start' init scripts for the new runlevel get executed and all services that should be running at this runlevel are started


*edit*
Btw, if you do roll your own custom solution
a better way to get the current runlevel is

runlevel | grep -o '[0-9]\+$'

[Jose Catre-Vandis]

Thanks amauk, and thanks for the one liner

I get what you are saying.

I had a look at directories rc2.d and rc3.d and they have exactly the same symlinks in each. Does that mean they do the same thing? Is it that I just haven't installed a program yet that needs a specific run-level to operate?

[amauk]

Doing a simple

CUR_RUNLVL=$(runlevel | grep -o '[0-9]\+$')
if [ "$CUR_RUNLVL" -eq 2 ]; then
	/usr/bin/slim
fi

is certainly easy,
but I do still have reservations about bypassing init scripts (which were designed for this very purpose, specifying what gets run at specific runlevels)

Certainly use rc.local as a first prototype,
but I would have an init script for SLiM as an end-goal

[Jose Catre-Vandis]

Well, I couldn't resist so i went ahead and tried it out.

Here is the script I put in /etc/rc.local:

!#/bin/bash

slimtest=`who -r`
runl=${slimtest:19:1}

#alt method
#slimtest=`runlevel | grep -o '[0-9]\+$'`

if [ "$runl" == "2" ]; then 

/usr/bin/slim

fi

I rebooted, selected the recovery mode menu entry, edited it to remove single and add a 3, pressed CTRL+X, and it booted up to a command prompt login

I logged in, checked dmesg, nothing odd there, and then typed startx.

runlevel | grep -o '[0-9]\+$'

returned "3"

Worked fine booted up the normal way too

Have more testing to do, and will have to see if I can break it!

[Jose Catre-Vandis]

I've also just had a look at the rc2.d and rc3.d directories on my main system which i have had running for over a year, updated from lucid to meerkat, and packages installed to the hilt, and loads of configuration. The contents of each folder are exactly the same.

So what have Ubuntu / Xubuntu been up to? Is there no difference at all between these two run-levels, aside from one supposedly being for cli mode?