Adding hibernation support to Ubuntu grub.cfg file

Question

Hi everyone,
I have a triple boot system being configured here (Win7, Ubuntu and Arch). I keep Win7 around because I have to deal with some MS Office files that sometimes won't work well in LibreOffice etc. Ubuntu is, now, my stable linux distro, and Arch is becoming my fast, personalized distro, for testing and playing around.
I'm trying to make Arch hibernate when I tell it to and come back successfully. I can, by now, make it hibernate, but it won't return to it's original state when I turn the computer on again (it boots like if I had a forced shutdown, checking filesystems etc). I already know that I have to add the "resume=my-swap-partition" line to grub.cfg, but grub is installed in Ubuntu, not Arch.
Now, to add the "resume=..." I should go to /etc/defaults/grub and add it to GRUB_CMDLINE_LINUX and run update-grub. But instead of adding it to Arch line in the grub.cfg, it adds to the Ubuntu one.
Can anyone help me how to add snnipet to Arch's grub.cfg line withou editing the file mannualy (which means I want to use the "correct" way that grub2 is suposed to be configured by)?
I hope I have been clear, English is not my first language. And I'm sorry if I posted in the wrong place, but I really didn't know where else to post. Thanks in advance for any reply.

Answer 1

You basically have two choices.
1. Change your installation so that Arch is controlling grub, and then use the method you describe above. Install grub from Arch, and use os-prober and update-grub to add an entry for Ubuntu.
2. Continue to allow Ubuntu to control grub, in which case you should really be asking for help on the Ubuntu forum, not here.
2a. If you continue to allow Ubuntu to control grub, you can copy your Arch entry from /boot/grub/grub.cfg into /etc/grub.d/40_custom, and then edit that file. If you are using os-prober to recreate your Arch entry when you update grub from Ubuntu, you should disable it (chmod -x /etc/grub.d/30_os-prober).