[laumars]

> ZFS licensing is an issue too, as it means that you can't just boot into any ol' Linux live CD (or remotely boot into a rescue environment) to fix the system or salvage the data on it.

Sure you can. I've done just this with 3 different live CDs: ArchLinux, FreeBSD and OpenSolaris. I'm fairly sure I've also used ZFS on the Ubuntu Desktop live CD as well but that was just for playing rather than rescusing a degraded system.

[vetinari]

FreeBSD and OpenSolaris probably aren't very useful, when trying to rescue a Linux system. Especially if you need to chroot and run things from there. (My need so far was to rescue non-booting system, because the zfs package upgrade went wrong and didn't update spl too. Re-running dracut would be a somewhat problematic from these two systems).

Ubuntu desktop live CD doesn't contain zfs, you have to install it from apt.

However, if you have a ZFS system, I see no problem with having an USB stick with minimal installation of your distro of choice, together with ZFS support. I'm glad I did have it since the ZFS install.

[laumars]

I think you're nitpicking a little to be honest. None of those problems are hard to workaround:

> FreeBSD and OpenSolaris probably aren't very useful, when trying to rescue a Linux system. Especially if you need to chroot and run things from there. (My need so far was to rescue non-booting system, because the zfs package upgrade went wrong and didn't update spl too. Re-running dracut would be a somewhat problematic from these two systems).

I do see your point but it really depends on the problem as not all recoveries require chroot / package management access. I've rescued Solaris (not OpenSolaris) with an OpenSuse live CD back when a cavalier opp chmodded /etc. I've rescued OpenSolaris with a FreeBSD CD back when a faulty RAID controller borked the file system. As for ArchLinux ISOs, I've used them to rescue more systems than I can count. But as you said, some problems do just require booting an instances of the host OS via some means.

> Ubuntu desktop live CD doesn't contain zfs, you have to install it from apt.

It took me all of about 10 minutes to bake the ZFS driver into the ISO. It's not hard compared to the other technical challenges you've discussed. Though if that's too much effort then I think you can also just apt it from the Live CD and manually modprobe it into the running kernel.

> However, if you have a ZFS system, I see no problem with having an USB stick with minimal installation of your distro of choice, together with ZFS support. I'm glad I did have it since the ZFS install.

Indeed. My preferred method is having rescue disks available over PXE booting. Before then I was forever hunting down my recovery disks or spare USB keys / CD-Rs. Not to mention the pain involved if the system I was trying to recover was my main workstation (ie the hardware I'd normally use to download and burn CDs on).

[vetinari]

> None of those problems are hard to workaround:

Sure, there are very few problems that cannot be solved by throwing some time and sweat on them. However, when I do need to solve something, I prefer to not be sidetracked by sub-problems. Smooth sailing and all that.

It's much simpler to pull an usb key from the drawer or PXE boot, as you mentioned, and go on on solving the damaged system, than to start downloading and preparing a live distro somewhere.

[laumars]

Again, you're overstating things. If it genuinely takes you more than a couple of minutes to run apt and modprobe then I really think you shouldn't be allowed anywere near a degraded system to begin with. These aren't "sub-problems" - they're the absolute basics of system administration.

[vetinari]

It a bit more than couple of minutes to download installer, install it somewhere (livecd doesn't have persistent /), install zfs there and only then go on doing whatever you were doing.

Compared to grabbing standard media you have somewhere, it will take at least 15 minutes extra.

Basics of system administration does not mean, that you are wasting your time, especially on something you can be without.

[laumars]

> It a bit more than couple of minutes to download installer, install it somewhere (livecd doesn't have persistent /), install zfs there and only then go on doing whatever you were doing.

You don't need a persistent root. I'd already addressed that point. Just run modprobe and you're done.

>Compared to grabbing standard media you have somewhere, it will take at least 15 minutes extra.

Bullshit. I've done exactly what I described and it did not take me 15 minutes. Furthermore all you're doing is pre-emptively pushing the work to before your outage which you could do the same with the ISO (if you really wanted to compare apples with apples).

> Basics of system administration does not mean, that you are wasting your time, especially on something you can be without.

The whole point of this tangent was about when one needs an Live CD. Not about whether creating a live CD is worthwhile when you already have a USB key. That new argument you've invented is stupid because the answer is quite clearly "use the USB key if that's already in your draw." But what happens if you have a ZFS volume on a system and you don't already have a recovery media? (ie the original question) Well in that case you can use any of the methods I described. Or, of course, you can create a USB key too. But that will take just as long as the methods I described anyway (you still have to download the OS image, ZFS drivers and write them all to your storage medium. Thus all you're really doing is swapping out one chunk of plastic with another chunk of plastic).