I've got CentOS 6 installed and am wondering if it's necessary to have installation media in order to run 'linux rescue'. (I have to do some LVM resizing and would rather do it from rescue mode than in a running system.)

What I've read about booting into linux rescue is that it seems to be necessary to have installation media and boot into that. But I'm wondering if it's possible to do it some other way, like from the grub menu? But it doesn't seem to be possible to enter 'linux rescue' from the grub command line (which I got to by typing 'c' in grub menu screen) - typing 'linux rescue' at grub command line says 'command not found'.

Maybe there's another way to do this? Or some fancy way to have loaded a rescue image or something onto my disk so I don't need installation media. There's 2 reasons why I'd like to enter linux rescue without installation media, both because my computer is very old. 1) My computer can't boot from USB, and 2) My CD/DVD tray is very unstable and keeps popping out intermittently, so I'd need to hold the tray in place during the whole LVM process and it's a real pain, and I wouldn't want to risk data corruption if the process is interrupted by my CD/DVD tray popping out.

I'm hoping there's some way - it'd also be nice to know how to do this if some urgent situation arose where I needed to enter linux rescue mode but didn't have installation media handy and it'd take to long to retrieve or create new installation media.

http://www.centos.org/docs/5/html/In...mode-boot.html

Rescue mode is for times then your system won't boot.

If you can't get the system to boot but using linux rescue then you have to boot to some media. It could be pxe, gpxe/ipxe, cd, usb or floppy maybe still.

Get a new CD drive. How much are they, if you need one you need one.

What jefro said

You may get away with it if the LVM you are fixing is not on the root partition; you should be able to umount it, but first ensure no process is using it.

That's one reason - the OP has another (equally valid) reason.
Must admit I'd go get another drive too - probably have one in my pile of "bits and pieces".

To answer the original question - no, you can't.
"linux rescue" in that context is a Redhat (CentOS) specific recovery environment. Grub loads it, but it has nothing to do with grub per se. Given that you managed a full CentOS install, I'd reckon you should be able to manage a rescue. Your call though.
Another option would be to dual boot another (possibly CentOS) system, and do your resizing from there. If CentOS, make sure you use different names for the LVM components so you can access them.
Won't help if your system is indeed unbootable from the hard-disk at any point.

A liveCD that has LVM and runs (completely) in RAM would also be an option - dsl/puppy/tinycore ... ? - haven't tried any in years.