From: raid5atemyhomework <raid5atemyhomework@protonmail.com>
To: "guix-devel@gnu.org" <guix-devel@gnu.org>
Subject: Re: ZFS on Guix
Date: Mon, 08 Feb 2021 02:13:13 +0000 [thread overview]
Message-ID: <BwsjjkFjW7wwYSYYp-YUhl5t1-1OtA8t3wbDftsQTZBXHNxcR2tBprzJmBYvNrMKnCeiu0d5bPz7V8IaKIdYu9NP7kDsd16z6gMPpR89-3c=@protonmail.com> (raw)
In-Reply-To: <VnQXBr-z8pdZxWrb6VtIu5pv0UeG1II5uUu4Q7BU3NsJMQbxhiQyWJE4fhEIWJO3VWrjetf1SMIu4_gi5r2AlYq8dADCXCDwW30RYaJ6seA=@protonmail.com>
Greetings guix-developers and other people trying to use Guix,
The patchset currently dying on issues.guix.gnu.org would provide a nice simple single-step way to enable *very basic* ZFS support on your Guix system. Until it gets merged, however, you can still enable *very very basic* ZFS support on your Guix system by following the below minimal guide.
First, select a Linux kernel that the latest ZFS package on Guix supports. Current on Guix is ZFS 2.0.1. That supports up to Linux 5.10. So I suggest using a `linux-libre-5.10` kernel. Don't go with the default `linux-libre` or `linux-libre-lts` since those could be updated to past what the ZFS on Guix supports, be explicit with what kernel version you have. Just remember to update to a later LTS version if ZFS on Guix ever gets updated to a later version.
Then, you need to create a ZFS package, by adding some declarations before the `operating-system` form:
```scheme
(use-modules #;...
(guix packages))
(use-package-modules #;... linux file-systems)
(define my-kernel linux-libre-5.10)
(define my-zfs
(package
(inherit zfs)
(arguments (cons* #:linux my-kernel (package-arguments zfs)))))
```
Then in the `operating-system` form, you need to add the following bits:
* Add ZFS to the kernel-loadable modules so that the installed kernel knows how to read and write ZFS disks.
* Add ZFS to the system profile packages so that you can easily manage ZFS disks.
So you have to modify a number of places:
```scheme
(operating-system
(kernel my-kernel)
(kernel-loadable-modules (list (list my-zfs "module")))
#;...
(packages
(append (map specification->package (list "nss-certs"))
(list my-zfs)
%base-packages))
#;...)
```
With the above you get a ***ridiculously minimal*** ZFS support.
* You have to `sudo modprobe zfs` explicitly at startup.
* You have to `sudo zpool import -a` explicitly at startup.
To do the above automatically at startup you need to add a Shepherd service to do the `zpool import`, and add a `kernel-module-loader` extension. This requires a bit more code to be added to your `configuration.scm`.
Here's what I got in my `configuration.scm`:
```scheme
(define zfs-shepherd-services
(let ((zpool (file-append my-zfs "/sbin/zpool"))
(zfs (file-append my-zfs "/sbin/zfs"))
(scheme-modules `((srfi srfi-1)
(srfi srfi-34)
(srfi srfi-35)
(rnrs io ports)
,@%default-modules)))
(define zfs-scan
(shepherd-service
(provision '(zfs-scan))
(documentation "Scans for ZFS pools.")
(requirement '(kernel-module-loader udev))
(modules scheme-modules)
(start #~(lambda _
(invoke/quiet #$zpool "import" "-a" "-N")))
(stop #~(const #f))))
(define zfs-automount
(shepherd-service
(provision '(zfs-automount))
(documentation "Automounts ZFS data sets.")
(requirement '(zfs-scan))
(modules scheme-modules)
(start #~(lambda _
(with-output-to-port
(current-error-port)
(lambda ()
(invoke #$zfs "mount" "-a" "-l")))))
(stop #~(lambda _
(chdir "/")
(invoke/quiet #$zfs "unmount" "-a" "-f")
#f))))
(list zfs-scan
zfs-automount)))
```
Then, add some `simple-service`s to your `operating-system`:
```scheme
(use-modules
#;...
(gnu services))
(use-service-modules linux shepherd #;...)
#;...
(operating-system
#;...
(services
(append
(list
#;...
(simple-service 'zfs-loader
kernel-module-loader-service-type
'("zfs"))
(simple-service 'zfs-shepherd-services
shepherd-root-service-type
zfs-shepherd-services)
(simple-service 'zfs-shepherd-services-user-processes
user-processes-service-type
'(zfs-automount))
#;...)
#;...
%desktop-services))
#;...)
```
The above lets you mount ZFS pools automatically at startup. Encrypted pools with `keylocation=prompt` will prompt at the console on bootup.
Caveats:
* You can't have a `/home` on ZFS mount. ZFS has to be mounted before `file-systems` target starts, otherwise Guix will fill up the root-mounr's `/home` directory and ZFS will refuse to mount over that. No `/` or `/boot` on ZFS either. Probably no good way to put `/gnu/store` on ZFS either, because Guix inherently assumes it's on the `/` mount.
* The above setup does not maintain a `/etc/zfs/zpool.cache` file, because I'm not really certain whether it's kosher in Guix to have a file maintained by ZFS in the `/etc` dir hierarchy. This has a number of consequences:
* `zdb` doesn't work because it looks for `/etc/zfs/zpool.cache`. Good luck trying to figure out why your pool is slow.
* You can't practically have more than a few dozen disks in your system, because the above uses `zpool import -a` which will cause ZFS to scan all the disks at bootup which would probably be slow if you have lots of disks.
* You can't practically use `zvol`s to back other filesystems in such a way that you can put them in a `file-system` declaration. Though why use any file-system other than ZFS amirite. You can still use `zvol`s to e.g. back a virtual machine that you launch manually when the system boot is finished, or from a Shepherd service that explicitly lists `user-processes` as a requirement. Though hmmm the above doesn't use `zvol_wait` anywhere... sigh.
* There's no ZED. No automatic replacement of failing drives with a hot spare. No monitoring. You can probably try launching it in its own Shepherd service, but you need to figure out how to populate `/etc/zfs/zed/` yourself. If you do, you probably will not be doing it from the `configuration.scm` file meaning it'll be hard to replicate the setup elsewhere.
Thanks
raid5atemyhomework
next prev parent reply other threads:[~2021-02-08 2:13 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-02 6:16 ZFS on Guix raid5atemyhomework
2021-01-02 6:40 ` raid5atemyhomework
2021-01-03 15:50 ` Danny Milosavljevic
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2021-01-04 0:50 ` raid5atemyhomework
2021-01-04 1:15 ` raid5atemyhomework
2021-01-05 11:02 ` raid5atemyhomework
2021-01-05 14:56 ` raid5atemyhomework
2021-01-06 0:59 ` Carlo Zancanaro
2021-01-06 3:50 ` raid5atemyhomework
2021-01-06 3:58 ` Carlo Zancanaro
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2021-01-06 4:41 ` raid5atemyhomework
2021-01-06 5:20 ` raid5atemyhomework
2021-01-06 15:58 ` raid5atemyhomework
2021-01-09 18:14 ` raid5atemyhomework
2021-01-10 5:17 ` raid5atemyhomework
2021-02-08 2:13 ` raid5atemyhomework [this message]
2021-02-08 3:51 ` Joshua Branson
2021-02-08 6:04 ` raid5atemyhomework
2021-02-08 6:13 ` raid5atemyhomework
2021-02-08 9:17 ` Maxime Devos
2021-02-08 9:32 ` raid5atemyhomework
2021-02-08 9:35 ` Maxime Devos
2021-02-10 8:29 ` Efraim Flashner
2021-02-08 2:16 ` Danny Milosavljevic
2021-02-10 7:37 ` raid5atemyhomework
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