[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).

[vetinari]

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

That assumes too much. For example, that you have a network connection while booted from the live media. You may not have one; then you cannot run apt/yum and you need persistent media that you prepared somewhere else. (Happened to me).

> Bullshit.

Surely. Or you have extra speedy USB keys. Just installing minimal distro on USB takes a better chunk of that time.

> The whole point of this tangent was about when one needs an Live CD.

When you are doing something non-standard - and installing ZFS on Linux is pretty nonstandard - you know in advance that the normal live media won't work. It's prudent to have something prepared, if/when SHTF event occurs.

Specifically with regards to filesystem, when you are installing with non-distro-provided-fs root, you need to make it anyway, just to install it in the first place. So instead of throwing it away, just label it and put in into the drawer. (When you are not installing on non-distro-fs root, you don't need support for that fs in live media at all, the standard one will do for making the system boot).

[laumars]

> That assumes too much

You've been assuming a crap load of stuff as well when it suits your argument. Like having a pre-prepared USB key to begin with.

> For example, that you have a network connection while booted from the live media. You may not have one; then you cannot run apt/yum and you need persistent media that you prepared somewhere else. (Happened to me).

Indeed. You might also not have a CD drive on the host (happened to me), or any blank CD-Rs, or a CD burner on your workstation. Or the internet connection might not work on your workstation either. But then most of those arguments can be made for creating a USB key as well so your point is moot. In fact my latest workstation (Macbook Pro) only has USB-C so I couldn't use my USB keys when I went to install Linux on that.

My point is, if you're looking for ways to nitpick, there are plenty for your examples as well. In fact there will be a thousand different exceptions for any solution you could dream up. Thus is the nature of working in IT.

> Just installing minimal distro on USB takes a better chunk of that time.

Arguably yes but that also takes longer and your original point was about getting stuff done as quickly as possible. So you're now contradicting yourself.

> When you are doing something non-standard - and installing ZFS on Linux is pretty nonstandard - you know in advance that the normal live media won't work.

Except the whole point of this tangent is me demonstrating where it does work.

> It's prudent to have something prepared, if/when SHTF event occurs.

Now you're arguing a different point to the point I was discussing. I'm not going to disagree with you there (since I've already discussed I run a PXE server for situations like these) but that wasn't the topic we were discussing.

I seriously just think you're now just arguing for the sake of winning an internet argument. I'm not going to argue with you that a CD is better than USB because it's pretty obvious that isn't the case. But that wasn't the point I was discussing. So for the benefit of my own sanity can we please get back onto topic: you can use live CDs to repair a degraded system running ZFS. Sure there will be occasions when you cannot; but that's the case when doing anything in IT (and thus why use sysadmins get to command such a good wage). But generally you can. And I literally have. Many times in fact. So enough with the dumb "death by a thousand paper cuts" and goal post moving arguments please.