Debian Buster Root on ZFS

Overview

Caution

  • This HOWTO uses a whole physical disk.

  • Do not use these instructions for dual-booting.

  • Backup your data. Any existing data will be lost.

System Requirements

Computers that have less than 2 GiB of memory run ZFS slowly. 4 GiB of memory is recommended for normal performance in basic workloads. If you wish to use deduplication, you will need massive amounts of RAM. Enabling deduplication is a permanent change that cannot be easily reverted.

Support

If you need help, reach out to the community using the zfs-discuss mailing list or IRC at #zfsonlinux on freenode. If you have a bug report or feature request related to this HOWTO, please file a new issue and mention @rlaager.

Contributing

  1. Fork and clone: https://github.com/openzfs/openzfs-docs

  2. Install the tools:

    sudo apt install pip3
    pip3 install -r requirements.txt
    # Add ~/.local/bin to your $PATH, e.g. by adding this to ~/.bashrc:
    PATH=$HOME/.local/bin:$PATH
    
  3. Make your changes.

  4. Test:

    cd docs
    make html
    sensible-browser _build/html/index.html
    
  5. git commit --signoff to a branch, git push, and create a pull request. Mention @rlaager.

Encryption

This guide supports three different encryption options: unencrypted, ZFS native encryption, and LUKS. With any option, all ZFS features are fully available.

Unencrypted does not encrypt anything, of course. With no encryption happening, this option naturally has the best performance.

ZFS native encryption encrypts the data and most metadata in the root pool. It does not encrypt dataset or snapshot names or properties. The boot pool is not encrypted at all, but it only contains the bootloader, kernel, and initrd. (Unless you put a password in /etc/fstab, the initrd is unlikely to contain sensitive data.) The system cannot boot without the passphrase being entered at the console. Performance is good. As the encryption happens in ZFS, even if multiple disks (mirror or raidz topologies) are used, the data only has to be encrypted once.

LUKS encrypts almost everything. The only unencrypted data is the bootloader, kernel, and initrd. The system cannot boot without the passphrase being entered at the console. Performance is good, but LUKS sits underneath ZFS, so if multiple disks (mirror or raidz topologies) are used, the data has to be encrypted once per disk.

Step 1: Prepare The Install Environment

  1. Boot the Debian GNU/Linux Live CD. If prompted, login with the username user and password live. Connect your system to the Internet as appropriate (e.g. join your WiFi network). Open a terminal.

  2. Setup and update the repositories:

    sudo vi /etc/apt/sources.list
    
    deb http://deb.debian.org/debian buster main contrib
    deb http://deb.debian.org/debian buster-backports main contrib
    
    sudo apt update
    
  3. Optional: Install and start the OpenSSH server in the Live CD environment:

    If you have a second system, using SSH to access the target system can be convenient:

    sudo apt install --yes openssh-server
    sudo systemctl restart ssh
    

    Hint: You can find your IP address with ip addr show scope global | grep inet. Then, from your main machine, connect with ssh user@IP.

  4. Become root:

    sudo -i
    
  5. Install ZFS in the Live CD environment:

    apt install --yes debootstrap gdisk dkms dpkg-dev \
        linux-headers-$(uname -r)
    apt install --yes -t buster-backports --no-install-recommends zfs-dkms
    modprobe zfs
    apt install --yes -t buster-backports zfsutils-linux
    
    • The dkms dependency is installed manually just so it comes from buster and not buster-backports. This is not critical.

    • We need to get the module built and loaded before installing zfsutils-linux or zfs-mount.service will fail to start.

Step 2: Disk Formatting

  1. Set a variable with the disk name:

    DISK=/dev/disk/by-id/scsi-SATA_disk1
    

    Always use the long /dev/disk/by-id/* aliases with ZFS. Using the /dev/sd* device nodes directly can cause sporadic import failures, especially on systems that have more than one storage pool.

    Hints:

    • ls -la /dev/disk/by-id will list the aliases.

    • Are you doing this in a virtual machine? If your virtual disk is missing from /dev/disk/by-id, use /dev/vda if you are using KVM with virtio; otherwise, read the troubleshooting section.

  2. If you are re-using a disk, clear it as necessary:

    If the disk was previously used in an MD array:

    apt install --yes mdadm
    
    # See if one or more MD arrays are active:
    cat /proc/mdstat
    # If so, stop them (replace ``md0`` as required):
    mdadm --stop /dev/md0
    
    # For an array using the whole disk:
    mdadm --zero-superblock --force $DISK
    # For an array using a partition:
    mdadm --zero-superblock --force ${DISK}-part2
    

    Clear the partition table:

    sgdisk --zap-all $DISK
    

    If you get a message about the kernel still using the old partition table, reboot and start over (except that you can skip this step).

  3. Partition your disk(s):

    Run this if you need legacy (BIOS) booting:

    sgdisk -a1 -n1:24K:+1000K -t1:EF02 $DISK
    

    Run this for UEFI booting (for use now or in the future):

    sgdisk     -n2:1M:+512M   -t2:EF00 $DISK
    

    Run this for the boot pool:

    sgdisk     -n3:0:+1G      -t3:BF01 $DISK
    

    Choose one of the following options:

    • Unencrypted or ZFS native encryption:

      sgdisk     -n4:0:0        -t4:BF00 $DISK
      
    • LUKS:

      sgdisk     -n4:0:0        -t4:8309 $DISK
      

    If you are creating a mirror or raidz topology, repeat the partitioning commands for all the disks which will be part of the pool.

  4. Create the boot pool:

    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 feature@zpool_checkpoint=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 /mnt \
        bpool ${DISK}-part3
    

    You should not need to customize any of the options for the boot pool.

    GRUB does not support all of the zpool features. See spa_feature_names in grub-core/fs/zfs/zfs.c. This step creates a separate boot pool for /boot with the features limited to only those that GRUB supports, allowing the root pool to use any/all features. Note that GRUB opens the pool read-only, so all read-only compatible features are “supported” by GRUB.

    Hints:

    • If you are creating a mirror topology, create the pool using:

      zpool create \
          ... \
          bpool mirror \
          /dev/disk/by-id/scsi-SATA_disk1-part3 \
          /dev/disk/by-id/scsi-SATA_disk2-part3
      
    • For raidz topologies, replace mirror in the above command with raidz, raidz2, or raidz3 and list the partitions from additional disks.

    • The pool name is arbitrary. If changed, the new name must be used consistently. The bpool convention originated in this HOWTO.

    Feature Notes:

    • The allocation_classes feature should be safe to use. However, unless one is using it (i.e. a special vdev), there is no point to enabling it. It is extremely unlikely that someone would use this feature for a boot pool. If one cares about speeding up the boot pool, it would make more sense to put the whole pool on the faster disk rather than using it as a special vdev.

    • The project_quota feature has been tested and is safe to use. This feature is extremely unlikely to matter for the boot pool.

    • The resilver_defer should be safe but the boot pool is small enough that it is unlikely to be necessary.

    • The spacemap_v2 feature has been tested and is safe to use. The boot pool is small, so this does not matter in practice.

    • As a read-only compatible feature, the userobj_accounting feature should be compatible in theory, but in practice, GRUB can fail with an “invalid dnode type” error. This feature does not matter for /boot anyway.

  5. Create the root pool:

    Choose one of the following options:

    • Unencrypted:

      zpool create \
          -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 mountpoint=/ -R /mnt \
          rpool ${DISK}-part4
      
    • ZFS native encryption:

      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 /mnt \
          rpool ${DISK}-part4
      
    • LUKS:

      apt install --yes cryptsetup
      cryptsetup luksFormat -c aes-xts-plain64 -s 512 -h sha256 ${DISK}-part4
      cryptsetup luksOpen ${DISK}-part4 luks1
      zpool create \
          -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 mountpoint=/ -R /mnt \
          rpool /dev/mapper/luks1
      

    Notes:

    • The use of ashift=12 is recommended here because many drives today have 4 KiB (or larger) physical sectors, even though they present 512 B logical sectors. Also, a future replacement drive may have 4 KiB physical sectors (in which case ashift=12 is desirable) or 4 KiB logical sectors (in which case ashift=12 is required).

    • Setting -O acltype=posixacl enables POSIX ACLs globally. If you do not want this, remove that option, but later add -o acltype=posixacl (note: lowercase “o”) to the zfs create for /var/log, as journald requires ACLs

    • Setting normalization=formD eliminates some corner cases relating to UTF-8 filename normalization. It also implies utf8only=on, which means that only UTF-8 filenames are allowed. If you care to support non-UTF-8 filenames, do not use this option. For a discussion of why requiring UTF-8 filenames may be a bad idea, see The problems with enforced UTF-8 only filenames.

    • recordsize is unset (leaving it at the default of 128 KiB). If you want to tune it (e.g. -o recordsize=1M), see these various blog posts.

    • Setting relatime=on is a middle ground between classic POSIX atime behavior (with its significant performance impact) and atime=off (which provides the best performance by completely disabling atime updates). Since Linux 2.6.30, relatime has been the default for other filesystems. See RedHat’s documentation for further information.

    • Setting xattr=sa vastly improves the performance of extended attributes. Inside ZFS, extended attributes are used to implement POSIX ACLs. Extended attributes can also be used by user-space applications. They are used by some desktop GUI applications. They can be used by Samba to store Windows ACLs and DOS attributes; they are required for a Samba Active Directory domain controller. Note that xattr=sa is Linux-specific. If you move your xattr=sa pool to another OpenZFS implementation besides ZFS-on-Linux, extended attributes will not be readable (though your data will be). If portability of extended attributes is important to you, omit the -O xattr=sa above. Even if you do not want xattr=sa for the whole pool, it is probably fine to use it for /var/log.

    • Make sure to include the -part4 portion of the drive path. If you forget that, you are specifying the whole disk, which ZFS will then re-partition, and you will lose the bootloader partition(s).

    • ZFS native encryption now defaults to aes-256-gcm.

    • For LUKS, the key size chosen is 512 bits. However, XTS mode requires two keys, so the LUKS key is split in half. Thus, -s 512 means AES-256.

    • Your passphrase will likely be the weakest link. Choose wisely. See section 5 of the cryptsetup FAQ for guidance.

    Hints:

    • If you are creating a mirror topology, create the pool using:

      zpool create \
          ... \
          bpool mirror \
          /dev/disk/by-id/scsi-SATA_disk1-part3 \
          /dev/disk/by-id/scsi-SATA_disk2-part3
      
    • For raidz topologies, replace mirror in the above command with raidz, raidz2, or raidz3 and list the partitions from additional disks.

    • When using LUKS with mirror or raidz topologies, use /dev/mapper/luks1, /dev/mapper/luks2, etc., which you will have to create using cryptsetup.

    • The pool name is arbitrary. If changed, the new name must be used consistently. On systems that can automatically install to ZFS, the root pool is named rpool by default.

Step 3: System Installation

  1. Create filesystem datasets to act as containers:

    zfs create -o canmount=off -o mountpoint=none rpool/ROOT
    zfs create -o canmount=off -o mountpoint=none bpool/BOOT
    

    On Solaris systems, the root filesystem is cloned and the suffix is incremented for major system changes through pkg image-update or beadm. Similar functionality has been implemented in Ubuntu 20.04 with the zsys tool, though its dataset layout is more complicated. Even without such a tool, the rpool/ROOT and bpool/BOOT containers can still be used for manually created clones. That said, this HOWTO assumes a single filesystem for /boot for simplicity.

  2. Create filesystem datasets for the root and boot filesystems:

    zfs create -o canmount=noauto -o mountpoint=/ rpool/ROOT/debian
    zfs mount rpool/ROOT/debian
    
    zfs create -o mountpoint=/boot bpool/BOOT/debian
    zfs mount bpool/BOOT/debian
    

    With ZFS, it is not normally necessary to use a mount command (either mount or zfs mount). This situation is an exception because of canmount=noauto.

  3. Create datasets:

    zfs create                                 rpool/home
    zfs create -o mountpoint=/root             rpool/home/root
    zfs create -o canmount=off                 rpool/var
    zfs create -o canmount=off                 rpool/var/lib
    zfs create                                 rpool/var/log
    zfs create                                 rpool/var/spool
    

    The datasets below are optional, depending on your preferences and/or software choices.

    If you wish to exclude these from snapshots:

    zfs create -o com.sun:auto-snapshot=false  rpool/var/cache
    zfs create -o com.sun:auto-snapshot=false  rpool/var/tmp
    chmod 1777 /mnt/var/tmp
    

    If you use /opt on this system:

    zfs create                                 rpool/opt
    

    If you use /srv on this system:

    zfs create                                 rpool/srv
    

    If you use /usr/local on this system:

    zfs create -o canmount=off                 rpool/usr
    zfs create                                 rpool/usr/local
    

    If this system will have games installed:

    zfs create                                 rpool/var/games
    

    If this system will store local email in /var/mail:

    zfs create                                 rpool/var/mail
    

    If this system will use Snap packages:

    zfs create                                 rpool/var/snap
    

    If you use /var/www on this system:

    zfs create                                 rpool/var/www
    

    If this system will use GNOME:

    zfs create                                 rpool/var/lib/AccountsService
    

    If this system will use Docker (which manages its own datasets & snapshots):

    zfs create -o com.sun:auto-snapshot=false  rpool/var/lib/docker
    

    If this system will use NFS (locking):

    zfs create -o com.sun:auto-snapshot=false  rpool/var/lib/nfs
    

    A tmpfs is recommended later, but if you want a separate dataset for /tmp:

    zfs create -o com.sun:auto-snapshot=false  rpool/tmp
    chmod 1777 /mnt/tmp
    

    The primary goal of this dataset layout is to separate the OS from user data. This allows the root filesystem to be rolled back without rolling back user data.

    If you do nothing extra, /tmp will be stored as part of the root filesystem. Alternatively, you can create a separate dataset for /tmp, as shown above. This keeps the /tmp data out of snapshots of your root filesystem. It also allows you to set a quota on rpool/tmp, if you want to limit the maximum space used. Otherwise, you can use a tmpfs (RAM filesystem) later.

  4. Install the minimal system:

    debootstrap buster /mnt
    

    The debootstrap command leaves the new system in an unconfigured state. An alternative to using debootstrap is to copy the entirety of a working system into the new ZFS root.

Step 4: System Configuration

  1. Configure the hostname:

    Replace HOSTNAME with the desired hostname:

    echo HOSTNAME > /mnt/etc/hostname
    vi /mnt/etc/hosts
    
    Add a line:
    127.0.1.1       HOSTNAME
    or if the system has a real name in DNS:
    127.0.1.1       FQDN HOSTNAME
    

    Hint: Use nano if you find vi confusing.

  2. Configure the network interface:

    Find the interface name:

    ip addr show
    

    Adjust NAME below to match your interface name:

    vi /mnt/etc/network/interfaces.d/NAME
    
    auto NAME
    iface NAME inet dhcp
    

    Customize this file if the system is not a DHCP client.

  3. Configure the package sources:

    vi /mnt/etc/apt/sources.list
    
    deb http://deb.debian.org/debian buster main contrib
    deb-src http://deb.debian.org/debian buster main contrib
    
    vi /mnt/etc/apt/sources.list.d/buster-backports.list
    
    deb http://deb.debian.org/debian buster-backports main contrib
    deb-src http://deb.debian.org/debian buster-backports main contrib
    
    vi /mnt/etc/apt/preferences.d/90_zfs
    
    Package: libnvpair1linux libuutil1linux libzfs2linux libzfslinux-dev libzpool2linux python3-pyzfs pyzfs-doc spl spl-dkms zfs-dkms zfs-dracut zfs-initramfs zfs-test zfsutils-linux zfsutils-linux-dev zfs-zed
    Pin: release n=buster-backports
    Pin-Priority: 990
    
  4. Bind the virtual filesystems from the LiveCD environment to the new system and chroot into it:

    mount --rbind /dev  /mnt/dev
    mount --rbind /proc /mnt/proc
    mount --rbind /sys  /mnt/sys
    chroot /mnt /usr/bin/env DISK=$DISK bash --login
    

    Note: This is using --rbind, not --bind.

  5. Configure a basic system environment:

    ln -s /proc/self/mounts /etc/mtab
    apt update
    
    apt install --yes locales
    dpkg-reconfigure locales
    

    Even if you prefer a non-English system language, always ensure that en_US.UTF-8 is available:

    dpkg-reconfigure tzdata
    
  6. Install ZFS in the chroot environment for the new system:

    apt install --yes dpkg-dev linux-headers-amd64 linux-image-amd64
    apt install --yes zfs-initramfs
    echo REMAKE_INITRD=yes > /etc/dkms/zfs.conf
    
  7. For LUKS installs only, setup /etc/crypttab:

    apt install --yes cryptsetup
    
    echo luks1 UUID=$(blkid -s UUID -o value ${DISK}-part4) none \
        luks,discard,initramfs > /etc/crypttab
    

    The use of initramfs is a work-around for cryptsetup does not support ZFS.

    Hint: If you are creating a mirror or raidz topology, repeat the /etc/crypttab entries for luks2, etc. adjusting for each disk.

  8. Install GRUB

    Choose one of the following options:

    • Install GRUB for legacy (BIOS) booting:

      apt install --yes grub-pc
      

      Select (using the space bar) all of the disks (not partitions) in your pool.

    • Install GRUB for UEFI booting:

        apt install dosfstools
        mkdosfs -F 32 -s 1 -n EFI ${DISK}-part2
        mkdir /boot/efi
        echo PARTUUID=$(blkid -s PARTUUID -o value ${DISK}-part2) \
           /boot/efi vfat nofail,x-systemd.device-timeout=1 0 1 >> /etc/fstab
        mount /boot/efi
        apt install --yes grub-efi-amd64 shim-signed
      
      **Notes:**
      
      • The -s 1 for mkdosfs is only necessary for drives which present

        4 KiB logical sectors (“4Kn” drives) to meet the minimum cluster size (given the partition size of 512 MiB) for FAT32. It also works fine on drives which present 512 B sectors.

      • For a mirror or raidz topology, this step only installs GRUB on the first disk. The other disk(s) will be handled later.

  9. Optional: Remove os-prober:

    dpkg --purge os-prober
    

    This avoids error messages from update-grub. os-prober is only necessary in dual-boot configurations.

  10. Set a root password:

    passwd
    
  11. Enable importing bpool

    This ensures that bpool is always imported, regardless of whether /etc/zfs/zpool.cache exists, whether it is in the cachefile or not, or whether zfs-import-scan.service is enabled.

    vi /etc/systemd/system/zfs-import-bpool.service
    
    [Unit]
    DefaultDependencies=no
    Before=zfs-import-scan.service
    Before=zfs-import-cache.service
    
    [Service]
    Type=oneshot
    RemainAfterExit=yes
    ExecStart=/sbin/zpool import -N -o cachefile=none bpool
    
    [Install]
    WantedBy=zfs-import.target
    
    systemctl enable zfs-import-bpool.service
    
  12. Optional (but recommended): Mount a tmpfs to /tmp

    If you chose to create a /tmp dataset above, skip this step, as they are mutually exclusive choices. Otherwise, you can put /tmp on a tmpfs (RAM filesystem) by enabling the tmp.mount unit.

    cp /usr/share/systemd/tmp.mount /etc/systemd/system/
    systemctl enable tmp.mount
    
  13. Optional (but kindly requested): Install popcon

    The popularity-contest package reports the list of packages install on your system. Showing that ZFS is popular may be helpful in terms of long-term attention from the distro.

    apt install --yes popularity-contest
    

    Choose Yes at the prompt.

Step 5: GRUB Installation

  1. Verify that the ZFS boot filesystem is recognized:

    grub-probe /boot
    
  2. Refresh the initrd files:

    update-initramfs -c -k all
    

    Note: When using LUKS, this will print “WARNING could not determine root device from /etc/fstab”. This is because cryptsetup does not support ZFS.

  3. Workaround GRUB’s missing zpool-features support:

    vi /etc/default/grub
    # Set: GRUB_CMDLINE_LINUX="root=ZFS=rpool/ROOT/debian"
    
  4. Optional (but highly recommended): Make debugging GRUB easier:

    vi /etc/default/grub
    # Remove quiet from: GRUB_CMDLINE_LINUX_DEFAULT
    # Uncomment: GRUB_TERMINAL=console
    # Save and quit.
    

    Later, once the system has rebooted twice and you are sure everything is working, you can undo these changes, if desired.

  5. Update the boot configuration:

    update-grub
    

    Note: Ignore errors from osprober, if present.

  6. Install the boot loader:

    1. For legacy (BIOS) booting, install GRUB to the MBR:

      grub-install $DISK
      

    Note that you are installing GRUB to the whole disk, not a partition.

    If you are creating a mirror or raidz topology, repeat the grub-install command for each disk in the pool.

    1. For UEFI booting, install GRUB to the ESP:

      grub-install --target=x86_64-efi --efi-directory=/boot/efi \
          --bootloader-id=debian --recheck --no-floppy
      

      It is not necessary to specify the disk here. If you are creating a mirror or raidz topology, the additional disks will be handled later.

  7. Fix filesystem mount ordering:

    We need to activate zfs-mount-generator. This makes systemd aware of the separate mountpoints, which is important for things like /var/log and /var/tmp. In turn, rsyslog.service depends on var-log.mount by way of local-fs.target and services using the PrivateTmp feature of systemd automatically use After=var-tmp.mount.

    mkdir /etc/zfs/zfs-list.cache
    touch /etc/zfs/zfs-list.cache/bpool
    touch /etc/zfs/zfs-list.cache/rpool
    ln -s /usr/lib/zfs-linux/zed.d/history_event-zfs-list-cacher.sh /etc/zfs/zed.d
    zed -F &
    

    Verify that zed updated the cache by making sure these are not empty:

    cat /etc/zfs/zfs-list.cache/bpool
    cat /etc/zfs/zfs-list.cache/rpool
    

    If either is empty, force a cache update and check again:

    zfs set canmount=on     bpool/BOOT/debian
    zfs set canmount=noauto rpool/ROOT/debian
    

    Stop zed:

    fg
    Press Ctrl-C.
    

    Fix the paths to eliminate /mnt:

    sed -Ei "s|/mnt/?|/|" /etc/zfs/zfs-list.cache/*
    

Step 6: First Boot

  1. Optional: Install SSH:

    apt install --yes openssh-server
    
    vi /etc/ssh/sshd_config
    # Set: PermitRootLogin yes
    
  2. Optional: Snapshot the initial installation:

    zfs snapshot bpool/BOOT/debian@install
    zfs snapshot rpool/ROOT/debian@install
    

    In the future, you will likely want to take snapshots before each upgrade, and remove old snapshots (including this one) at some point to save space.

  3. Exit from the chroot environment back to the LiveCD environment:

    exit
    
  4. Run these commands in the LiveCD environment to unmount all filesystems:

    mount | grep -v zfs | tac | awk '/\/mnt/ {print $3}' | \
        xargs -i{} umount -lf {}
    zpool export -a
    
  5. Reboot:

    reboot
    

    Wait for the newly installed system to boot normally. Login as root.

  6. Create a user account:

    Replace username with your desired username:

    zfs create rpool/home/username
    adduser username
    
    cp -a /etc/skel/. /home/username
    chown -R username:username /home/username
    usermod -a -G audio,cdrom,dip,floppy,netdev,plugdev,sudo,video username
    
  7. Mirror GRUB

    If you installed to multiple disks, install GRUB on the additional disks.

    • For legacy (BIOS) booting:

      dpkg-reconfigure grub-pc
      

      Hit enter until you get to the device selection screen. Select (using the space bar) all of the disks (not partitions) in your pool.

    • For UEFI booting:

      umount /boot/efi
      

      For the second and subsequent disks (increment debian-2 to -3, etc.):

      dd if=/dev/disk/by-id/scsi-SATA_disk1-part2 \
         of=/dev/disk/by-id/scsi-SATA_disk2-part2
      efibootmgr -c -g -d /dev/disk/by-id/scsi-SATA_disk2 \
          -p 2 -L "debian-2" -l '\EFI\debian\grubx64.efi'
      
      mount /boot/efi
      

Step 7: Optional: Configure Swap

Caution: On systems with extremely high memory pressure, using a zvol for swap can result in lockup, regardless of how much swap is still available. There is a bug report upstrea.

  1. Create a volume dataset (zvol) for use as a swap device:

    zfs create -V 4G -b $(getconf PAGESIZE) -o compression=zle \
        -o logbias=throughput -o sync=always \
        -o primarycache=metadata -o secondarycache=none \
        -o com.sun:auto-snapshot=false rpool/swap
    

    You can adjust the size (the 4G part) to your needs.

    The compression algorithm is set to zle because it is the cheapest available algorithm. As this guide recommends ashift=12 (4 kiB blocks on disk), the common case of a 4 kiB page size means that no compression algorithm can reduce I/O. The exception is all-zero pages, which are dropped by ZFS; but some form of compression has to be enabled to get this behavior.

  2. Configure the swap device:

    Caution: Always use long /dev/zvol aliases in configuration files. Never use a short /dev/zdX device name.

    mkswap -f /dev/zvol/rpool/swap
    echo /dev/zvol/rpool/swap none swap discard 0 0 >> /etc/fstab
    echo RESUME=none > /etc/initramfs-tools/conf.d/resume
    

    The RESUME=none is necessary to disable resuming from hibernation. This does not work, as the zvol is not present (because the pool has not yet been imported) at the time the resume script runs. If it is not disabled, the boot process hangs for 30 seconds waiting for the swap zvol to appear.

  3. Enable the swap device:

    swapon -av
    

Step 8: Full Software Installation

  1. Upgrade the minimal system:

    apt dist-upgrade --yes
    
  2. Install a regular set of software:

    tasksel

  3. Optional: Disable log compression:

    As /var/log is already compressed by ZFS, logrotate’s compression is going to burn CPU and disk I/O for (in most cases) very little gain. Also, if you are making snapshots of /var/log, logrotate’s compression will actually waste space, as the uncompressed data will live on in the snapshot. You can edit the files in /etc/logrotate.d by hand to comment out compress, or use this loop (copy-and-paste highly recommended):

    for file in /etc/logrotate.d/* ; do
        if grep -Eq "(^|[^#y])compress" "$file" ; then
            sed -i -r "s/(^|[^#y])(compress)/\1#\2/" "$file"
        fi
    done
    
  4. Reboot:

    reboot
    

Step 9: Final Cleanup

  1. Wait for the system to boot normally. Login using the account you created. Ensure the system (including networking) works normally.

  2. Optional: Delete the snapshots of the initial installation:

    sudo zfs destroy bpool/BOOT/debian@install
    sudo zfs destroy rpool/ROOT/debian@install
    
  3. Optional: Disable the root password:

    sudo usermod -p '*' root
    
  4. Optional (but highly recommended): Disable root SSH logins:

    If you installed SSH earlier, revert the temporary change:

    vi /etc/ssh/sshd_config
    # Remove: PermitRootLogin yes
    
    systemctl restart ssh
    
  5. Optional: Re-enable the graphical boot process:

    If you prefer the graphical boot process, you can re-enable it now. If you are using LUKS, it makes the prompt look nicer.

    sudo vi /etc/default/grub
    # Add quiet to GRUB_CMDLINE_LINUX_DEFAULT
    # Comment out GRUB_TERMINAL=console
    # Save and quit.
    
    sudo update-grub
    

    Note: Ignore errors from osprober, if present.

  6. Optional: For LUKS installs only, backup the LUKS header:

    sudo cryptsetup luksHeaderBackup /dev/disk/by-id/scsi-SATA_disk1-part4 \
        --header-backup-file luks1-header.dat
    

    Store that backup somewhere safe (e.g. cloud storage). It is protected by your LUKS passphrase, but you may wish to use additional encryption.

    Hint: If you created a mirror or raidz topology, repeat this for each LUKS volume (luks2, etc.).

Troubleshooting

Rescuing using a Live CD

Go through Step 1: Prepare The Install Environment.

For LUKS, first unlock the disk(s):

apt install --yes cryptsetup
cryptsetup luksOpen /dev/disk/by-id/scsi-SATA_disk1-part4 luks1
# Repeat for additional disks, if this is a mirror or raidz topology.

Mount everything correctly:

zpool export -a
zpool import -N -R /mnt rpool
zpool import -N -R /mnt bpool
zfs load-key -a
zfs mount rpool/ROOT/debian
zfs mount -a

If needed, you can chroot into your installed environment:

mount --rbind /dev  /mnt/dev
mount --rbind /proc /mnt/proc
mount --rbind /sys  /mnt/sys
chroot /mnt /bin/bash --login
mount /boot
mount -a

Do whatever you need to do to fix your system.

When done, cleanup:

exit
mount | grep -v zfs | tac | awk '/\/mnt/ {print $3}' | \
    xargs -i{} umount -lf {}
zpool export -a
reboot

Areca

Systems that require the arcsas blob driver should add it to the /etc/initramfs-tools/modules file and run update-initramfs -c -k all.

Upgrade or downgrade the Areca driver if something like RIP: 0010:[<ffffffff8101b316>]  [<ffffffff8101b316>] native_read_tsc+0x6/0x20 appears anywhere in kernel log. ZoL is unstable on systems that emit this error message.

MPT2SAS

Most problem reports for this tutorial involve mpt2sas hardware that does slow asynchronous drive initialization, like some IBM M1015 or OEM-branded cards that have been flashed to the reference LSI firmware.

The basic problem is that disks on these controllers are not visible to the Linux kernel until after the regular system is started, and ZoL does not hotplug pool members. See https://github.com/zfsonlinux/zfs/issues/330.

Most LSI cards are perfectly compatible with ZoL. If your card has this glitch, try setting ZFS_INITRD_PRE_MOUNTROOT_SLEEP=X in /etc/default/zfs. The system will wait X seconds for all drives to appear before importing the pool.

QEMU/KVM/XEN

Set a unique serial number on each virtual disk using libvirt or qemu (e.g. -drive if=none,id=disk1,file=disk1.qcow2,serial=1234567890).

To be able to use UEFI in guests (instead of only BIOS booting), run this on the host:

sudo apt install ovmf
sudo vi /etc/libvirt/qemu.conf

Uncomment these lines:

nvram = [
   "/usr/share/OVMF/OVMF_CODE.fd:/usr/share/OVMF/OVMF_VARS.fd",
   "/usr/share/OVMF/OVMF_CODE.secboot.fd:/usr/share/OVMF/OVMF_VARS.fd",
   "/usr/share/AAVMF/AAVMF_CODE.fd:/usr/share/AAVMF/AAVMF_VARS.fd",
   "/usr/share/AAVMF/AAVMF32_CODE.fd:/usr/share/AAVMF/AAVMF32_VARS.fd"
]
sudo systemctl restart libvirtd.service

VMware

  • Set disk.EnableUUID = "TRUE" in the vmx file or vsphere configuration. Doing this ensures that /dev/disk aliases are created in the guest.