Clearly, they should have used windows



  • When BSOD goes open source



  • I wonder what happens when you skip mounting /.


  • sockdevs

    @Maciejasjmj said:

    I wonder what happens when you skip mounting /.

    Kernel Panic

    not surprising really.



  • TRWTF is not using a server os



  • You can run Ubuntu on a server. In fact, the server hosting this forum is running Ubuntu on Ubuntu running on a server.



  • It that a nested Ubuntu setup or just an English fail?



  • Discourse runs on a Docker (VM) image with ubuntu in a host running Ubuntu.



  • I see. So it is somewhat nested. If either ubuntu fails, then it will be part of that 4 hours of downtime we had last month?

    And somewhat related to that picture, I'd see that quite a bit for one of my secondary disks. Eventually I just removed it from fstab, so I didn't get bothered by it when booting up.
    2 out of my 4 drives are hosed on this machine, but I won't worry much until the 3rd goes. Then again, I could just boot from usb if I really had to (maybe I should start backing up the configuration files for that day).



  • @Nprz said:

    If either ubuntu fails, then it will be part of that 4 hours of downtime we had last month?

    I suppose they are using some HA setup where a VM or host crashing wouldn't affect site uptime.



  • @Maciejasjmj said:

    I wonder what happens when you skip mounting /

    Generally you'll end up looking at an error message saying that the rootfs couldn't be found and a busybox shell prompt (busybox is built into the initramfs, as are the initscripts and/or systemd that run those pre-mount disk checks).



  • @Nprz said:

    Eventually I just removed it from fstab, so I didn't get bothered by it when booting up.

    You can leave it in the fstab and just set its "pass" field to 0, if you'd prefer it to be automounted without ever being checked.



  • Docker is a container, not a virtual machine. Like a Solaris Zone or a Free BSD jail, it's not another instance of the OS running on top of the host with a hypervisor but is an isolated set of resources controlled by the kernel.
    Unless something here's been configured weirdly, of course.



  • @Nprz said:

    So it is somewhat nested. If either ubuntu fails, then it will be part of that 4 hours of downtime we had last month?

    Docker images don't actually nest the OS, they just containerize an application.

    From the application's point of view it appears to be the only thing running on the OS, but that's just because the kernel is hiding other processes and assorted resources from it. There is only the one kernel running though.



  • I'd be worried it would cause some process to hang when it traverses the file system for something. I prefer to not mount anything I don't need at that moment.
    My server on the other hand has all my valuable drives mounted. I just rarely access them unless I need something.



  • Well, yeah. It isn't a real virtual machine but it likely thinks it is running Ubuntu (even if the real is was centos). But if one of the libraries on the container or the OS are buggy enough it could go down.
    I had enough hell with openvz back in the day. I'm skeptical of dockers and other containers being some silver bullet. But faster deployment and less resource use are nice features.



  • @Nprz said:

    it likely thinks it is running Ubuntu (even if the real is was centos)

    Eh? How would that work? It still sees the host as itself, it just doesn't see everything else sharing the host.



  • I've never used docker so I don't know.
    With openvz you gave it whatever you wanted to see. So if you wanted it running a flavor of Ubuntu you give it that. But I guess not much is shared with the base OS. Not all the containers would have to run the same image though (using union fs save disk space if you do though).
    So docker sounds to be lighter weight.



  • Apologies, it probably is possible like that with Docker (or similar) then if it's possible with OpenVz - as long as they all work with the same kernel version.

    I've not played with Linux containers like Docker, just UNIX variations like Solaris Jails.


  • Discourse touched me in a no-no place

    @Nprz said:

    With openvz you gave it whatever you wanted to see. So if you wanted it running a flavor of Ubuntu you give it that. But I guess not much is shared with the base OS. Not all the containers would have to run the same image though (using union fs save disk space if you do though).

    With Docker, about the only thing that must be shared is the kernel itself. I believe that having two different Linux variations on top of that common foundation is entirely possible; there are Debian, Ubuntu and Centos base images available for sure (and maybe more; I didn't search very hard!) though you'd usually want to start from something a bit higher level (e.g., Ubuntu + PostgreSQL + Rails) to save yourself quite a bit of effort.



  • Different distros are known to compile their kernels with different options, so the path of least surprise will always be to keep to the same distro if possible; libraries supplied with e.g. Debian might well make different assumptions about what kernel facilities are available than those supplied with e.g. Fedora.


  • Discourse touched me in a no-no place

    @flabdablet said:

    Different distros are known to compile their kernels with different options, so the path of least surprise will always be to keep to the same distro if possible; libraries supplied with e.g. Debian might well make different assumptions about what kernel facilities are available than those supplied with e.g. Fedora.

    At the very least, that'd be why you use a standard build of the distro rather than baking your own. (I also thought that distributions modified the kernel less than they used to, at least unless you're doing desktop systems — but then you wouldn't use Docker — or are getting involved with something more exotic like AFS.)



  • I'm sure there would end up being very few if any surprises impossible to work around, but given the choice I'd use the same distro across the board. Admin would also be a bit easier given a consistent userland in all containers.


  • Discourse touched me in a no-no place

    Our experience is that not everything is easy. The big one to watch out for isn't the version of things, but rather whether the software is happy with the NAT rules. Some things get very confused by that sort of thing, especially by the fact that addresses and ports seen by users might be different from any that the application knows about.



  • They forgot to update the DONT_PANIC setting.


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