1: # Root On ZFS
3: NetBSD-9 gained much improved ZFS support.
4: However, one feature it's still missing is the ability to have your system
5: root on ZFS.
6: For that, we need to teach our boot loader about ZFS,xi
7: but until then we can work around this limitation by using a FFS boot
8: partition and a ZFS root ramdisk.
9: You'll also need to use NetBSD-9.99.48 or newer.
11: The idea is simple - the boot loader loads the NetBSD kernel and the
12: required modules *(solaris and zfs)* from FFS and the ZFS root ramdisk.
13: The ramdisk then imports the ZFS root pool called `rpool`,
14: mounts `rpool/ROOT` to `/altroot` and finally instructs the kernel to
15: chroot to it.
16: Because the initial root is on a ramdisk,
17: we can then load the boot partition from inside the ZFS chroot to maintain it;
18: for example to update the kernel and modules.
20: ## Assumptions
22: The ramdisk does make some assumptions as there is no way to pass variables
23: from boot.cfg:
25: * The kernel has matching modules installed in the same partition; you only need `solaris` and `zfs`.
26: * The ZFS root pool is called `rpool` and the root filesystem is called `ROOT`.
28: Once inside the chroot the kernel will load modules from the ZFS filesystem
29: because there is a symlink to it from the ramdisk.
30: The same is true for any firmware needed after boot.
32: ## Generic setup
34: Until the NetBSD installer can be updated, here are the manual steps from fresh:
36: * Build the ramdisk (`cd src/distrib/amd64/ramdisks/ramdisk-zfsroot; nbmake-amd64`)
37: * Boot the NetBSD installer
38: * Create a small (I used 2G) FFS partition and a normal swap partition
39: * Create a partition for ZFS
40: * Finish the NetBSD installation - install the etc, base and maybe rescue sets
41: * Reboot into your minimal NetBSD install
43: ## ZFS Setup
45: So far, so good. Now we need to make the needed adjustments to change root:
47: * Create a ZFS pool called `rpool` on your ZFS partition
48: * Create a ZFS filesystem called `ROOT` in `rpool`
49: * Set the mountpoint of `rpool/ROOT` to legacy so that the mount command can deal with it
50: * Create any other ZFS filesystems you want to - if you create `/usr` or `/var` or anything in these they **must** to be legacy mount points as well
51: * `zfs umount rpool/ROOT`
52: * Add `rpool/ROOT /altroot zfs rw` to /etc/fstab
53: * `mount /altroot`
54: * Extract the sets you need to `/altroot`. At a minimum you will need etc and base.
55: * `cd /altroot/dev; ./MAKEDEV all`
56: * `cd /altroot; mkdir kern proc`
57: * Copy `/etc/wscons.conf`, `/etc/fstab` and any other config files sysinst might have created to `/etc/rc.conf` to `/altroot/etc`
58: * Set `zfs=YES` in `/altroot/etc/rc.conf`
59: * Remove `rpool/ROOT` from `/altroot/etc/fstab`
60: * Add `name=boot /altroot ffs rw,noauto` to `/altroot/etc/fstab` along with any ZFS filesytems you created in '/usr' and '/var'
61: * Add the filesystems as well to `critical_filesystems_local` in `/altroot/etc/rc.conf` - such as `critical_filesystems_local="/usr /var /var/log"`
62: * Copy the `ramdisk-zfsroot.fs` to `/`
63: * Edit `/boot.cfg` and add `menu=Boot ZFS Root:load solaris;load zfs;fs /ramdisk-zfsroot.fs;boot`
65: And done!
66: You can now reboot and enjoy your root on ZFS and all the benefits it brings.
67: When updating the kernel, remember to `mount /altroot` and update it there as
68: well as the modules.
70: ## Future work
72: All these steps could be done in the installer.
73: This is probably an easier task than adding ZFS support to the bootloader.
74: But don't let that stop you if you are stuck for something to do!
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