docs(tazjin/install-zfs): Add some notes for the ZFS installs I do

I have to google all of this this each time otherwise.

Change-Id: Ib7df0882e4681bd061f77a00b678641a7f37c58c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5546
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: tazjin <tazjin@tvl.su>
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Vincent Ambo 2022-05-09 15:26:58 +02:00 committed by tazjin
parent 155902744b
commit 09f27d278d

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Current steps for my NixOS-on-ZFS installs with impermanence.
## Target layout (example from tverskoy):
Partitioning:
```
nvme0n1 259:0 0 238.5G 0 disk
├─nvme0n1p1 259:1 0 128M 0 part /boot (type: EFI system)
└─nvme0n1p2 259:2 0 238.3G 0 part (type: Solaris root)
```
ZFS layout:
```
NAME USED AVAIL REFER MOUNTPOINT
zpool 212G 19.0G 248K /zpool
zpool/ephemeral 668M 19.0G 192K /zpool/ephemeral
zpool/ephemeral/home 667M 19.0G 667M legacy
zpool/local 71.3G 19.0G 192K /zpool/local
zpool/local/nix 71.3G 19.0G 71.3G legacy
zpool/safe 140G 19.0G 192K /zpool/safe
zpool/safe/depot 414M 19.0G 414M legacy
zpool/safe/persist 139G 19.0G 139G legacy
```
With reset-snapshots:
```
NAME USED AVAIL REFER MOUNTPOINT
zpool/ephemeral/home@blank 144K - 192K -
zpool/ephemeral/home@tazjin-clean 144K - 200K -
```
Legacy mountpoints are used because the NixOS wiki advises that using
ZFS own mountpoints might lead to issues with the mount order during
boot.
## Install steps
1. First, get internet.
2. Use `fdisk` to set up the partition layout above (fwiw, EFI type
should be `1`, Solaris root should be `66`).
3. Format the first partition for EFI: `mkfs.fat -F32 -n EFI $part1`
4. Init ZFS stuff:
```
zpool create \
# 2 SSD only settings
-o ashift=12 \
-o autotrim=on \
-R /mnt \
-O canmount=off \
-O mountpoint=none \
-O acltype=posixacl \
-O compression=lz4 \
-O atime=off \
-O xattr=sa \
-O encryption=aes-256-gcm \
-O keylocation=prompt \
-O keyformat=passphrase \
zpool $part2
```
Reserve some space for deletions:
```
zfs create -o refreservation=1G -o mountpoint=none zpool/reserved
```
Create the datasets as per the target layout:
```
# Throwaway datasets
zfs create -o canmount=off -o mountpoint=none zpool/ephemeral
zfs create -o mountpoint=legacy zpool/ephemeral/root
zfs create -o mountpoint=legacy zpool/ephemeral/home
# Persistent datasets
zfs create -o canmount=off -o mountpoint=none zpool/persistent
zfs create -o mountpoint=legacy zpool/persistent/nix
zfs create -o mountpoint=legacy zpool/persistent/depot
zfs create -o mountpoint=legacy zpool/persistent/data
```
Create completely blank snapshots of the ephemeral datasets:
```
zfs snapshot zpool/ephemeral/root@blank
zfs snapshot zpool/ephemeral/home@blank
```
The ephemeral home volume needs the user folder already set up with
permissions. Mount it and create the folder there:
```
mount -t zfs zpool/ephemeral/root /mnt
mkdir /mnt/home
mount -t zfs zpool/ephemeral/home /mnt/home
mkdir /mnt/home/tazjin
chmod 1000:100 /mnt/home/tazjin
zfs snapshot zpool/ephemeral/home@tazjin-clean
```
Now the persistent Nix store volume can be mounted and installation
can begin.
```
mkdir /mnt/nix
mount -t zfs zpool/persistent/nix /mnt/nix
```
4. Configure & install NixOS as usual.