Fedora 10 Snapshot 1 on the XO

As the Fedora 10 release cycle moves forward, we are now in the stage where there are regular “snapshot” releases planned for every week. These snapshots are just a 'point in time' test of rawhide and released based on whether they work and if not, then we end up just waiting for the next week. The intent is to keep the required effort level relatively low but still give a basis for testing between the beta and the preview release.

On Friday, the first of these post-beta snapshots was released. This includes a set of live images which can run without modifications on the OLPC. This is nice as it will make me not have to do builds of images and host them on fedorapeople anymore 🙂

With this image plus the updated livecd-iso-to-disk, the performance of the image on the XO is much better. How is this achieved? The single biggest thing that helps is changing to putting the ext3fs on the SD card as opposed to the squashfs. This means we're not paying the penalty of decompression. The downside is that this requires a 4 GB (or more) SD card as opposed to a 2 GB one.

A second thing which helps (significantly) is not using a RAM based overlay and instead putting the overlay on the SD card. There are some upsides and some downsides to doing this, but at this point, the upsides seem to outweigh the downsides. This will even more be the case for this week's snapshot with a few of the things I'm planning to have ready for that (more details below…).

So that said, what is the invocation of livecd-iso-to-disk that I'm using (and thus would recommend to testers)? Presently, it's

~/src/fedora/livecd-tools/tools/livecd-iso-to-disk.sh –force –xo –overlay-size-mb 512 – ~/Desktop/Live/F10-Snap1-i686-Live.iso /dev/mmcblk0p1

This sets up a 512 MB (persistent) overlay on the SD card and with –xo, we set up a boot/olpc.fth as well as moving over the embedded ext3fs instead of the squashfs.

So the obvious question is what's next/on my plate to make sure is in better shape for this week's snapshot?

  • Fix up handling so that we can easily set up having some swap on the SD card. This again feels like a situation where we're better off doing than not. Most of the mechanism should be present in Snap1, but for some reason, I'm not seeing /mnt/live being properly mounted from the live initscript. This should be a pretty straight-forward thing if someone wanted to take a look and send me a patch 🙂 The live initscript itself lives in the spin-kickstarts repo
  • Non-persistent, disk-based overlay. The “persistence” is kind of kludgey in that it can pretty easily fill up and cause problems. Unfortunately, with dm-snapshot, there's not a lot we can do about that. Hopefully we'll get some form of unionfs in the future, but that definitely won't land for F10. This should just be a matter of changing the initrd to recognize a flag and recreate the snapshot store on the SD card when requested. The initrd is created from mkliveinitrd in the mkinitrd package.
  • Persistent /home on the internal nand (mtd0). Again, this should be mostly ready to go with Snap1, but was acting weird the end of last week for me. Should get mounted within the live initscript
  • Start making a dent in some of the reported bugs
  • Investigate the question which was asked of just sticking the ext3fs on the SD card directly and not doing the “normal” live image bits for the overlay. While this is interesting to explore, I have a sinking suspicion that it's not something that's really doable in the timeframe of Fedora 10, although it is certainly one that bears looking at more for Fedora 11.

2 thoughts on “Fedora 10 Snapshot 1 on the XO”

  1. I was wondering, why ext3 and not the new UBIFS ? I read it was designed specifically for this kind of usage (the article on lwn even mentions OLPC), couldn’t it help ?

  2. ubifis is only for use on bare flash, not flash through a controller which is what you have with SD and the like.

    ubifs is being investigated for use with the internal flash on the OLPC to replace jffs2 which is currently being used.

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