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I'm having trouble booting my netbook so I'm looking at the grub boot parameters.

I know what splash, quite and vt.handoff=7 do. However I can't find any documentation anywhere about what ro does and why it's there, even though it appears in most examples of grub start up code.

Where can I find documentation about ro?

I assume it means read only. Though docs would ease my mind.

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2 Answers 2

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ro means 'mount the file system as read-only'.

the reason this is done is because fsck (the file system checker) should never be run on a read/write file system.

it's a default for a very good reason, and i would be very wary of changing it.

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    also you might find this interesting if you're exploring your boot options: cyberciti.biz/tips/…
    – thomasmichaelwallace
    Dec 2, 2011 at 22:41
  • As a sidenote, in theory you could do without specifying ro, because the kernel image defaults to this option (script init: readonly=y). And after the boot-time scripts have done their work (mounting, fsck, logo...), the partition is remounted (mountall) as per options in /etc/fstab (which usually means it is rw).
    – arrange
    Dec 2, 2011 at 23:21
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Boot options can be handled by either the kernel itself or the init script in an initrd/initramfs.

The options that are handled as part of the 'vanilla' kernel are documented on this page (can also be found other places as well, but that was the first one I found). The boot parameters handled by Ubuntu's initramfs can be found here.

The vt.handoff parameter is a bit weird. What it does is explained in this askubuntu answer:

For a smooth boot process, we want to display something other than a black screen as early as possible and leave it on screen until the desktop is ready. vt.handoff=7 is part of this. We have the boot loader display an aubergine background (we wanted to have an Ubuntu logo as well, but there are problems with different aspect ratios between the boot loader and the real system, so this is the next best thing). vt.handoff=7 then causes the kernel to maintain the current contents of video memory on virtual terminal 7, which is a new "transparent" VT type. The first time that the kernel is told to switch away from VT 7, either from Plymouth or manually (Alt-F1, etc.), these contents are lost and VT 7 reverts to text mode.

I could only find a description of it from bug reports, but this bug report tells it's origins:

vt.handoff is a module parameter introduced in an Ubuntu-specific SAUCE patch by Andy Whitcroft, ...It was written expressly for use in the Ubuntu boot process...

Because of this, any documentation would probably be with the module source (if such documentation exists).

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