Root on ZFS with native encryption: Difference between revisions

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= Objectives =
This is a guide for installing Alpine Linux with its root partition on an encrypted ZFS volume, using ZFS's own encryption capabilities. The system will be encrypted when powered off and will need to be unlocked by typing a passphrase at boot. To be able to boot the system, the `/boot` partition remains unencrypted.
This guide aims to setup encrypted Alpine Linux on ZFS with a layout compatible with boot environments. Mirror and RAID-Z supported.


Except EFI system partition and boot pool {{ic|/boot}}, everything is encrypted. Root pool is encrypted with ZFS native encryption and swap partition is encrypted with dm-crypt.
= OpenZFS Guide =


To do an unencrypted setup, simply omit {{ic|-O keylocation -O keyformat}} when creating root pool.
A guide on OpenZFS website supports native encryption, UEFI boot and legacy boot, and multi-disk.  See [https://openzfs.github.io/openzfs-docs/Getting%20Started/Alpine%20Linux/Root%20on%20ZFS.html here].


= Notes =
= Downloading Alpine =
== Swap on ZFS will cause dead lock ==
You shouldn't use a ZVol as a swap device, as it can deadlock under memory pressure. See [https://github.com/openzfs/zfs/issues/7734] This guide will set up swap on a separate partition with plain dm-crypt.


Resume from swap is not possible, because the key of swap partition can not be stored in the unencrypted boot pool. Busybox initramfs only supports unlocking exactly one LUKS container at boot, therefore boot pool and swap partition can not be both LUKS encrypted. A possible workaround is to import and mount boot pool after booting the system via systemd service.
Download the '''extended''' release from https://www.alpinelinux.org/downloads/ as only it contains the zfs kernel modules at the time of writing (2022-02-12).


== Resume from ZFS will corrupt the pool ==
Write it to a USB device and boot from it.
ZFS does not support freeze/thaw operations, which is required for resuming from hibernation, or suspend to disk. Attempt to resume from a swap on ZFS '''WILL''' corrupt the pool. See [https://github.com/openzfs/zfs/issues/260]
== Encrypted boot pool ==
GRUB supports booting from LUKS-1 encrypted containers. Therefore, it is possible to encrypt both boot pool and root pool to achieve full disk encryption.


To do this, format boot pool partition as LUKS-1 container and supply the encryption password here. Use keyfile for root pool and embed the keyfile in initramfs.
= Initial Setup =


Since there isn't any sensitive information in {{ic|/boot}} anyway (unless you want to use a persistent LUKS encrypted swap partition for resume from hibernation), encrypting boot pool provides no meaningful benefit and complicates the installation and recovery process.
Run the following to start the installation procedure:


= Pre-installation =
{{cmd|setup-alpine}}
UEFI is required. Supports single disk & multi-disk (stripe, mirror, RAID-Z) installation.


'''Existing data on target disk(s) will be destroyed.'''
Answer all the questions, and hit {{Key|Ctrl}}+{{Key|C}} when prompted for which disk you'd like to use.


Download the '''extended''' release from https://www.alpinelinux.org/downloads/, it's shipped with ZFS kernel module.
== Optional: SSH access ==


Write it to a USB and boot from it.
This section is optional and it assumes internet connectivity. You may enable sshd so you can ssh into the box and copy and paste the rest of the commands from these instructions into a terminal window.


== Setup live environment ==
Edit {{path|/etc/ssh/sshd_config}} and search for `Permit`. Change the value after `PermitRootLogin` to read `yes`
Run the following command to setup the live environment, select disk=none at the last step when asked for disk mode. See [[Installation#Questions_asked_by_setup-alpine]].
setup-alpine
The settings given here will be copied to the target system later by {{ic|setup-disk}}.


== Install system utilities ==
save and exit to shell. Run {{codeline|service sshd restart}}
apk update
apk add eudev sgdisk grub-efi zfs
modprobe zfs
Here we must install eudev to have persistent block device names. '''Do not use''' /dev/sda for ZFS pools.
rc-update add udev-trigger sysinit
/etc/init.d/udev-trigger start


= Variables =
Now you can ssh in as root. Do not forget to go back and comment this line out when you're done since it will be enabled on the resulting machine. You will be reminded again at the end of this doc.
In this step, we will set some variables to make our installation process easier.
DISK=/dev/disk/by-id/ata-HXY_120G_YS
Use unique disk path instead of {{ic|/dev/sda}} to ensure the correct partition can be found by ZFS.


Other variables
= Add required packages =
TARGET_USERNAME='your username'
ENCRYPTION_PWD='your root pool encryption password'
TARGET_USERPWD='user account password'
Create a mountpoint
  MOUNTPOINT=`mktemp -d`
Create a unique suffix for the ZFS pools: this will prevent name conflict when importing pools on another Root on ZFS system.
poolUUID=$(dd if=/dev/urandom of=/dev/stdout bs=1 count=100 2>/dev/null |tr -dc 'a-z0-9' | cut -c-6)


= Partitioning =
{{cmd|apk add {{pkg|zfs}} {{pkg|sfdisk}} {{pkg|e2fsprogs}} {{pkg|syslinux}}}}
For a single disk, UEFI installation, we need to create at lease 3 partitions:
* EFI system partition
* Boot pool partition
* Root pool partition
Since [[GRUB]] only partially support ZFS, many features needs to be disabled on the boot pool. By creating a separate root pool, we can then utilize the full potential of ZFS.


Clear the partition table on the target disk and create EFI, boot and root pool parititions:
= Partition setup =
sgdisk --zap-all $DISK
sgdisk -n1:0:+512M -t1:EF00 $DISK
sgdisk -n2:0:+2G $DISK        # boot pool
sgdisk -n3:0:0 $DISK          # root pool
If you want to use a multi-disk setup, such as mirror or RAID-Z, partition every target disk with the same commands above.


== Optional: Swap partition ==
We're assuming that {{path|/dev/sda}} is the target storage device here and in the rest of the document, but the name of the storage device you wish to install to may be different. To see a list of storage devices and determine the correct one, type {{codeline|sfdisk -l}}.
[[Swap]] support on ZFS is also problematic, therefore it is recommended to create a separate Swap partition if needed. This guide will cover the creation of a separate swap partition.(can not be used for hibernation since the encryption key is discarded when power off.)


If you want to use swap, reserve some space at the end of disk when creating root pool:
{{cmd|echo -e "/dev/sda1: start{{=}}1M,size{{=}}100M,bootable\n/dev/sda2: start{{=}}101M" | sfdisk --quiet --label dos /dev/sda}}
sgdisk -n3:0:-8G $DISK        # root pool, reserve 8GB for swap at the end of the disk
sgdisk -n4:0:0 $DISK          # swap partition


= Boot and root pool creation =
== Create device nodes ==
As mentioned above, ZFS features need to be selectively enabled for GRUB. All available features are enabled when no {{ic|feature@}} is supplied.


Here we explicitly enable those GRUB can support.
{{cmd|mdev -s}}
zpool create \
    -o ashift=12 -d \
    -o feature@async_destroy=enabled \
    -o feature@bookmarks=enabled \
    -o feature@embedded_data=enabled \
    -o feature@empty_bpobj=enabled \
    -o feature@enabled_txg=enabled \
    -o feature@extensible_dataset=enabled \
    -o feature@filesystem_limits=enabled \
    -o feature@hole_birth=enabled \
    -o feature@large_blocks=enabled \
    -o feature@lz4_compress=enabled \
    -o feature@spacemap_histogram=enabled \
    -O acltype=posixacl -O canmount=off -O compression=lz4 \
    -O devices=off -O normalization=formD -O relatime=on -O xattr=sa \
    -O mountpoint=/boot -R $MOUNTPOINT \
    bpool_$poolUUID $DISK-part2
Nothing is stored directly under bpool and rpool, hence {{ic|1=canmount=off}}. The respective {{ic|mountpoint}} properties are more symbolic than practical.


For root pool all available features are enabled by default
== Create the {{path|/boot}} filesystem ==
echo $ENCRYPTION_PWD | zpool create \
    -o ashift=12 \
    -O encryption=aes-256-gcm \
    -O keylocation=prompt -O keyformat=passphrase \
    -O acltype=posixacl -O canmount=off -O compression=lz4 \
    -O dnodesize=auto -O normalization=formD -O relatime=on \
    -O xattr=sa -O mountpoint=/ -R $MOUNTPOINT \
    rpool_$poolUUID $DISK-part3


== Notes for multi-disk ==
{{cmd|mkfs.ext4 /dev/sda1}}
For mirror:
zpool create \
    ... \
    bpool_$poolUUID mirror \
    /dev/disk/by-id/target_disk1-part2 \
    /dev/disk/by-id/target_disk2-part2
zpool create \
    ... \
    rpool_$poolUUID mirror \
    /dev/disk/by-id/target_disk1-part3 \
    /dev/disk/by-id/target_disk2-part3
For RAID-Z, replace mirror with raidz, raidz2 or raidz3.


= Dataset creation =
= ZFS setup =
This layout is intended to separate root file system from persistent files. See [https://wiki.archlinux.org/index.php/User:M0p/Root_on_ZFS_Native_Encryption/Layout] for a description.
== Create the root zpool ==
{{Text art|<nowiki>
zfs create -o canmount=off -o mountpoint=none rpool_$poolUUID/HOME
zfs create -o canmount=off -o mountpoint=none rpool_$poolUUID/ROOT
zfs create -o canmount=off -o mountpoint=none bpool_$poolUUID/BOOT
zfs create -o mountpoint=/ -o canmount=noauto rpool_$poolUUID/ROOT/default
zfs create -o mountpoint=/boot -o canmount=noauto bpool_$poolUUID/BOOT/default
zfs mount rpool_$poolUUID/ROOT/default
zfs mount bpool_$poolUUID/BOOT/default
d='usr var var/lib'
for i in $d; do zfs create  -o canmount=off rpool_$poolUUID/ROOT/default/$i; done
d='srv usr/local'
for i in $d; do zfs create rpool_$poolUUID/ROOT/default/$i; done
d='log spool tmp'
for i in $d; do zfs create rpool_$poolUUID/ROOT/default/var/$i; done
zfs create -o mountpoint=/home rpool_$poolUUID/HOME/default
zfs create -o mountpoint=/root rpool_$poolUUID/HOME/default/root
zfs create rpool_$poolUUID/HOME/default/$TARGET_USERNAME
</nowiki>}}


= Format and mount EFI partition =
{{cmd|modprobe zfs
mkfs.vfat -n EFI $DISK-part1
zpool create -f -o ashift{{=}}12 \
mkdir $MOUNTPOINT/boot/efi
-O acltype{{=}}posixacl -O canmount{{=}}off -O compression{{=}}lz4 \
mount $DISK-part1 $MOUNTPOINT/boot/efi
-O dnodesize{{=}}auto -O normalization{{=}}formD -O relatime{{=}}on -O xattr{{=}}sa \
-O encryption{{=}}aes-256-gcm -O keylocation{{=}}prompt -O keyformat{{=}}passphrase \
-O mountpoint{{=}}/ -R /mnt \
rpool /dev/sda2}}


= Install Alpine Linux to target disk =
You will have to enter your passphrase at this point. Choose wisely, as your passphrase is most likely [https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions#5-security-aspects the weakest link in this setup].
== Preparations ==
GRUB will not find the correct path of root device without ZPOOL_VDEV_NAME_PATH=YES.
export ZPOOL_VDEV_NAME_PATH=YES
setup-disk refuse to run on ZFS by default, we need to add ZFS to the supported filesystem array.
sed -i 's|supported="ext|supported="zfs ext|g' /sbin/setup-disk


== Run setup-disk ==
A few notes on the options supplied to zpool:
BOOTLOADER=grub USE_EFI=y setup-disk -v $MOUNTPOINT
<ul>
Note that grub-probe will still fail despite ZPOOL_VDEV_NAME_PATH=YES variable set above. We will deal with this later inside chroot.
<li>{{codeline|ashift{{=}}12}} is recommended here because many drives today have 4KiB (or larger) physical sectors, even though they present 512B logical sectors</li>
<li>{{codeline|acltype{{=}}posixacl}} enables POSIX ACLs globally</li>
<li>{{codeline|normalization{{=}}formD}} eliminates some corner cases relating to UTF-8 filename normalization. It also enables `utf8only=on`, meaning that only files with valid UTF-8 filenames will be accepted.</li>
<li>{{codeline|xattr{{=}}sa}} vastly improves the performance of extended attributes, but is Linux-only. If you care about using this pool on other OpenZFS implementation don't specify this option.</li></ul>


= Chroot into new system =
After completing this, confirm that the pool has been created:
mount --rbind /dev  $MOUNTPOINT/dev
mount --rbind /proc $MOUNTPOINT/proc
mount --rbind /sys  $MOUNTPOINT/sys
chroot $MOUNTPOINT /usr/bin/env TARGET_USERPWD=$TARGET_USERPWD TARGET_USERNAME=$TARGET_USERNAME poolUUID=$poolUUID /bin/sh


= Finish GRUB installation =
{{cmd|# zpool status}}
As GRUB installation failed half-way in [[#Run setup-disk]], we will finish it here.


Apply GRUB ZFS fix:
Should return something like:
export ZPOOL_VDEV_NAME_PATH=YES
Generate grub.cfg
grub-mkconfig -o /boot/grub/grub.cfg
WARNING: as of 3.12.3, the Alpine Linux version of GRUB (not upstream version) can not properly detect ZFS root device. A temporary fix: The correct root device, rpool_$poolUUID/ROOT/default is missing from grub.cfg, fix with a sed command
sed -i "s|root=PARTUUID.*|root=ZFS=rpool_$poolUUID/ROOT/default|g" /boot/grub/grub.cfg


= Install packages =
      pool: rpool
These packages are used for creating a common user account. Root account is accessed with sudo. Also package for persisitent block device name must be installed.
    state: ONLINE
apk add shadow sudo eudev
      scan: none requested
    config:
   
        NAME        STATE    READ WRITE CKSUM
        rpool      ONLINE      0    0    0
          sda2      ONLINE      0    0    0
   
    errors: No known data errors


= Enable ZFS services =
== Create the required datasets and mount root ==
rc-update add zfs-import sysinit
rc-update add zfs-mount sysinit
rc-update add zfs-zed sysinit
rc-update add udev-trigger sysinit


= Enable sudo access for wheel group =
{{cmd|zfs create -o mountpoint{{=}}none -o canmount{{=}}off rpool/ROOT
mv /etc/sudoers /etc/sudoers.original
zfs create -o mountpoint{{=}}legacy rpool/ROOT/alpine
tee /etc/sudoers << EOF
mount -t zfs rpool/ROOT/alpine /mnt/}}
root ALL=(ALL) ALL
%wheel ALL=(ALL) ALL
EOF


= Add normal user account =
== Mount the {{path|/boot}} filesystem ==
useradd -s /bin/bash -U -G wheel,video -d /home/$TARGET_USERNAME $TARGET_USERNAME
chown -R $TARGET_USERNAME:$TARGET_USERNAME /home/$TARGET_USERNAME
echo "$TARGET_USERNAME:$TARGET_USERPWD" | chpasswd


= Finish installation =
{{cmd|mkdir /mnt/boot/
Take a snapshot for the clean installation for future use and export all pools.
mount -t ext4 /dev/sda1 /mnt/boot/}}
exit
zfs snapshot -r rpool_$poolUUID/ROOT/default@install
zfs snapshot -r bpool_$poolUUID/BOOT/default@install
Pools must be exported before reboot, or they will fail to be imported on boot.
mount | grep -v zfs | tac | grep $MOUNTPOINT | awk '{print $3}' | \
  xargs -i{} umount -lf {}
zpool export bpool_$poolUUID
zpool export rpool_$poolUUID


= Reboot =
== Enable ZFS' services ==
As of this writing, the initramfs lacks support for entering ZFS password at boot. When booting the system, root dataset will simply fail to mount and drop into emergency shell.


We need to manually load the key and mount root dataset with
{{cmd|rc-update add zfs-import sysinit
zfs load-key -a
rc-update add zfs-mount sysinit}}
# enter password
 
mount -t zfs rpool_$poolUUID/ROOT/default /sysroot
= Install Alpine Linux =
ArchZFS project solved this with a sh script, available [https://github.com/archzfs/archzfs/blob/master/src/zfs-utils/zfs-utils.initcpio.hook here].
 
{{cmd|setup-disk /mnt
dd if{{=}}/usr/share/syslinux/mbr.bin of{{=}}/dev/sda # write mbr so we can boot}}
 
= Reboot and enjoy! =
 
😉
 
'''NOTE:'''
If you went with the optional step, be sure to disable root login after you reboot.

Latest revision as of 17:18, 21 August 2023

This is a guide for installing Alpine Linux with its root partition on an encrypted ZFS volume, using ZFS's own encryption capabilities. The system will be encrypted when powered off and will need to be unlocked by typing a passphrase at boot. To be able to boot the system, the `/boot` partition remains unencrypted.

OpenZFS Guide

A guide on OpenZFS website supports native encryption, UEFI boot and legacy boot, and multi-disk. See here.

Downloading Alpine

Download the extended release from https://www.alpinelinux.org/downloads/ as only it contains the zfs kernel modules at the time of writing (2022-02-12).

Write it to a USB device and boot from it.

Initial Setup

Run the following to start the installation procedure:

setup-alpine

Answer all the questions, and hit Ctrl+C when prompted for which disk you'd like to use.

Optional: SSH access

This section is optional and it assumes internet connectivity. You may enable sshd so you can ssh into the box and copy and paste the rest of the commands from these instructions into a terminal window.

Edit /etc/ssh/sshd_config and search for `Permit`. Change the value after `PermitRootLogin` to read `yes`

save and exit to shell. Run service sshd restart

Now you can ssh in as root. Do not forget to go back and comment this line out when you're done since it will be enabled on the resulting machine. You will be reminded again at the end of this doc.

Add required packages

apk add zfs sfdisk e2fsprogs syslinux

Partition setup

We're assuming that /dev/sda is the target storage device here and in the rest of the document, but the name of the storage device you wish to install to may be different. To see a list of storage devices and determine the correct one, type sfdisk -l.

echo -e "/dev/sda1: start=1M,size=100M,bootable\n/dev/sda2: start=101M" | sfdisk --quiet --label dos /dev/sda

Create device nodes

mdev -s

Create the /boot filesystem

mkfs.ext4 /dev/sda1

ZFS setup

Create the root zpool

modprobe zfs zpool create -f -o ashift=12 \ -O acltype=posixacl -O canmount=off -O compression=lz4 \ -O dnodesize=auto -O normalization=formD -O relatime=on -O xattr=sa \ -O encryption=aes-256-gcm -O keylocation=prompt -O keyformat=passphrase \ -O mountpoint=/ -R /mnt \ rpool /dev/sda2

You will have to enter your passphrase at this point. Choose wisely, as your passphrase is most likely the weakest link in this setup.

A few notes on the options supplied to zpool:

  • ashift=12 is recommended here because many drives today have 4KiB (or larger) physical sectors, even though they present 512B logical sectors
  • acltype=posixacl enables POSIX ACLs globally
  • normalization=formD eliminates some corner cases relating to UTF-8 filename normalization. It also enables `utf8only=on`, meaning that only files with valid UTF-8 filenames will be accepted.
  • xattr=sa vastly improves the performance of extended attributes, but is Linux-only. If you care about using this pool on other OpenZFS implementation don't specify this option.

After completing this, confirm that the pool has been created:

# zpool status

Should return something like: 

     pool: rpool
    state: ONLINE
     scan: none requested
   config:
   
       NAME        STATE     READ WRITE CKSUM
       rpool       ONLINE       0     0     0
         sda2      ONLINE       0     0     0
   
   errors: No known data errors

Create the required datasets and mount root

zfs create -o mountpoint=none -o canmount=off rpool/ROOT zfs create -o mountpoint=legacy rpool/ROOT/alpine mount -t zfs rpool/ROOT/alpine /mnt/

Mount the /boot filesystem

mkdir /mnt/boot/ mount -t ext4 /dev/sda1 /mnt/boot/

Enable ZFS' services

rc-update add zfs-import sysinit rc-update add zfs-mount sysinit

Install Alpine Linux

setup-disk /mnt dd if=/usr/share/syslinux/mbr.bin of=/dev/sda # write mbr so we can boot

Reboot and enjoy!

😉

NOTE: If you went with the optional step, be sure to disable root login after you reboot.

Retrieved from "https://wiki.alpinelinux.org/w/index.php?title=Root_on_ZFS_with_native_encryption&oldid=24380"