Can't boot a btrfs partition

[doctordruidphd]

As of 11.04 it is possible to use only btrfs file systems with the caveat that grub _MUST_NOT_ be installed to the boot sector of the btrfs volume containing /boot. As long as your booting via MBR, you can have /boot within /

The system boots from the MBR, which points to /dev/sda1. What I mean is that there is no separate /boot partition, /boot is inside the 11.10 system. Sorry if I didn't make that clear.

I did some more experimenting, and what I found is that as soon as I do an "insmod btrfs" in a grub boot stanza, it fails to find anything, period. So either there is a bug here, or I have missed some very basic point of how to do this. The only thing I haven't tried yet is a separate /boot inside the btrfs, which I will try as per james147's suggestion today.

In the end, I don't think btrfs is going to do all that much for me as I don't seem to be doing anything that creates the problems it was designed to address. Just really wanted to experiment with the latest and greatest. From what I have read, to implement btrfs to any advantage would mean re-thinking the way the whole system is set up. That may best be put off until 12.10, as it sounds like Canonical isn't contemplating full support for it until then.

I will keep experimenting, though -- that's what this is for.

[james147]

I will keep experimenting, though -- that's what this is for.

You could also try a clean install inside a vm, if your goal is just to play around with it that that's probably the easiest solution.

I think I might give 11.10 and 12.04 a try in a vm with btrfs as default see what I can find.

[oshunluvr]

Sorry drdru, but /dev/sda1 doesn't contain an MBR. The MBR is on /dev/sda. /dev/sda1 (a partition) contains a PBR (Partition Boot Record). The difference can be critical to booting, but it sounds like maybe you've just mis-spoken and you meant to refer to /dev/sda. You can boot from a PBR, but only via chainloading from the MBR.

If I was to guess, the whole circular thing you've set up could be part of the problem. Have you tried a more simple approach like installing to a single partition?

[doctordruidphd]

it sounds like maybe you've just mis-spoken and you meant to refer to /dev/sda.

Yeah, what I meant is the system boots from the MBR, the grub menu that is loaded comes from /boot on the system on sda1.
Really the whole things is quite simple, there is just either some basic fact about how to boot a btrfs file system that I haven't gotten straight, or there is some bug or as yet unimplemented feature that is getting in the way.

I have pretty much dropped this, I hadn't planned on it being a major problem. I also thought btrfs was going to be the default for 12.04, but apparently that is no longer the case, so there's no hurry to straighten it out. Kind of pressed for time on other things. Thanks for the help, will return to the issue when time permits.

[GreyGeek]

I installed BalsalmPro 12.1 (which contains Plasma-Active-One), just to get an idea of what Plasma-Active-Two would be like. It's going to run the Spark tablet. I noticed during the installation of the openSUSE clone that it offered btrfs as the FS, so I selected it. It is very fast and stable, at least for as long as I played with it. For the most part I don't think most people will notice the difference between it and EXT4, unless they are adding and removing disks a lot.

[oshunluvr]

GG is right. The real advantages to btrfs are snapshots, the ability to add or remove devices on the fly, and multidisk RAID performance. IMO unless you're using these features, most users won't need to switch to btrfs. I do think it's faster than ext4 when properly configured and if you have multiple disks you should be using it now. I'm extremely comfortable using mdadm RAID and btrfs is so easy in comparison it's boring.

The only real caveat it this point is the missing fsck tool and some GUI utilities to allow the average user take advantage of the added features. I suspect we'll see these in the next year.

[james147]

The only real caveat it this point is the missing fsck tool and some GUI utilities to allow the average user take advantage of the added features. I suspect we'll see these in the next year.

I am currently writing a python wrapper around the btrfs tool, if anyone is interested its available on github. Though its still early days I have mostly implemented the subvolume commands.