Difference between revisions of "Installing Arch Linux on ZFS"

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[[Category:Getting and installing Arch]]
 
[[Category:Getting and installing Arch]]
{{Article summary start}}
+
[[ja:ZFS に Arch Linux をインストール]]
{{Article summary text|This article describes the necassary procedures for installing Arch Linux onto a ZFS root filesystem.}}
+
{{Related articles start}}
{{Article summary heading|Related}}
+
{{Related|ZFS}}
{{Article summary wiki|ZFS}}
+
{{Related|Experimenting with ZFS}}
{{Article summary wiki|ZFS on FUSE}}
+
{{Related|ZFS on FUSE}}
{{Article summary end}}
+
{{Related articles end}}
 +
This article details the steps required to install Arch Linux onto a ZFS root filesystem.
  
The [[Wikipedia:ZFS|Zettabyte File System (ZFS)]] is an advanced [[Wikipedia:Copy-on-write|copy-on-write]] filesystem designed to preserve data integrity from a multitude of possible corruption scenarios as well as provide simple administration features. ZFS makes disk administration effortless with support ZFS storage pools (zpools) and automatic mount handling. First released in 2005 for Solaris OS, ZFS has since become the flag bearer for next generation filesystems.
+
== Installation ==
  
ZFS was first developed and released by Sun (now owned by Oracle) as [[Wikipedia:Open source software|Open Source Software]] licensed under the [[Wikipedia:Common Development and Distribution License|Common Development and Distribution License]] (CDDL) which is famously [http://arstechnica.com/information-technology/2010/06/uptake-of-native-linux-zfs-port-hampered-by-license-conflict/ incompatible with the GNU Public License]. This incompatibility prevents ZFS from being merged into the mainline kernel, and generally presents some obstacles for users that want to use ZFS in Linux.
+
See [[ZFS#Installation]] for installing the ZFS packages. If installing Arch Linux onto ZFS from the archiso, it would be easier to use the [[Unofficial user repositories#archzfs|archzfs]] repository.
  
[http://zfsonlinux.org/ ZFSonLinux.org] is a project funded by the [https://www.llnl.gov/ Lawrence Livermore National Laboratory] to develop a native Linux kernel module for its massive storage requirements and super computers.
+
=== Embedding archzfs into archiso ===
  
==Notes before installation==
+
See [[ZFS#Embed_the_archzfs_packages_into_an_archiso|ZFS]] article.
  
* This guide uses the unofficial archzfs repository hosted at http://demizerone.com/archzfs. This repository is maintained by Jesus Alvarez and is signed with his PGP key: [http://pgp.mit.edu:11371/pks/lookup?op=vindex&search=0x5E1ABF240EE7A126 0EE7A126].
+
=== Arch ZFS installation scripts ===
  
* The ZFS packages are tied to the kernel version they were built against. This means it will not be possible to perform kernel updates until new packages (or package sources) are released by the ZFS package maintainer.
+
Manually installing Arch using ZFS is quite an involved undertaking but thankfully there are scripts to simplify the process such as [https://github.com/danboid/ALEZ ALEZ] and [https://bitbucket.org/avi9526/install-raidz/src install-raidz].
  
* This guide currently targets UEFI compatible systems. It should be relatively easy to install ZFS on bios compatible systems using this guide. The sections for BIOS installations exist in this article as stubs to allow easy contributions of content.
+
== Partition the destination drive ==
  
==Boot from the installation media==
+
Review [[Partitioning]] for information on determining the partition table type to use for ZFS. ZFS supports GPT and MBR partition tables.
  
It is a good idea make an installation media with the needed software included. Otherwise, you will need the latest archiso installation media burned to a CD or a USB key.  
+
ZFS manages its own partitions, so only a basic partition table scheme is required. The partition that will contain the ZFS filesystem should be of the type {{ic|bf00}}, or "Solaris Root".
  
To embed {{ic|zfs}} in the archiso, download the {{ic|archiso}} package.
+
When using GRUB as your bootloader with an MBR partition table there is no need for a BIOS boot partition. Drives larger than 2TB require a GPT partition table and you should use {{Pkg|parted}} to create the partitions for GPT. BIOS/GPT and UEFI/GPT configurations require a small (1/2MB) BIOS boot partition to store the bootloader. If you are using a UEFI-only bootloader you should use GPT.
  
Start the process:
+
Depending upon your choice of bootloader you may or may not require an EFI partition. GRUB, when installed on a BIOS machine (or a UEFI machine booting in legacy mode) using either MBR or GPT doesn't require an EFI partition. Consult [[Boot loaders]] for more info.
  # cp -r /usr/share/archiso/configs/releng /root/media
+
  
Edit the {{ic|packages.x86_64}} file adding those lines:
+
=== Partition scheme ===
  spl-utils
+
  spl
+
  zfs-utils
+
  zfs
+
  
Edit the {{ic|pacman.conf}} file adding those lines (TODO, correctly embed keys in the installation media?):
+
Here is an example of a basic partition scheme that could be employed for your ZFS root install on a BIOS/MBR installation using GRUB:
  [archzfs]
+
  SigLevel = Never
+
  Server = <nowiki>http://demizerone.com/$repo/core/$arch</nowiki>
+
  
Add other packages in {{ic|packages.both}}, {{ic|packages.i686}}, or {{ic|packages.x86_64}} if needed and create the image.
+
{{bc|<nowiki>
   # ./build -v
+
Part    Size   Type
 +
----    ----  -------------------------
 +
  1    XXXG  Solaris Root (bf00)</nowiki>
 +
}}
  
The image will be in the {{ic|/root/media/out}} directory.
+
Using GRUB on a BIOS (or UEFI machine in legacy boot mode) machine but using a GPT partition table:
  
More informations about the process can be read in [http://kroweer.wordpress.com/2011/09/07/creating-a-custom-arch-linux-live-usb/ this guide] or in the [Archiso] article.
+
{{bc|<nowiki>
 
+
Part    Size  Type
If you are installing onto a UEFI system, see [[Unified Extensible Firmware Interface#Create UEFI bootable USB from ISO]] for creating UEFI compatible installation media.
+
----    ----  -------------------------
 
+
  1      2M  BIOS boot partition (ef02)
==Setup pacman==
+
  2    XXXG  Solaris Root (bf00)</nowiki>
 +
}}
  
Activate the required network connection and then edit {{ic|/etc/pacman.d/mirrorlist}} and configure the mirrors for pacman to use.  Once that is done, edit {{ic|/etc/pacman.conf}} and add the archzfs repository:
+
Another example, this time using a UEFI-specific bootloader (such as [[rEFInd]]) and GPT:
  
{{hc|# nano /etc/pacman.conf|<nowiki>
+
{{bc|<nowiki>
[archzfs]
+
Part    Size  Type
Server = http://demizerone.com/$repo/core/$arch</nowiki>
+
----    ----  -------------------------
 +
  1      2M  BIOS boot partition (ef02)
 +
  2    100M  EFI boot partition (ef00)
 +
  3    XXXG  Solaris Root (bf00)</nowiki>
 
}}
 
}}
  
Next, add the archzfs maintainer's PGP key to the local trust:
+
ZFS does not support swap files. If you require a swap partition, see [[ZFS#Swap volume]] for creating a swap ZVOL.
  
    # pacman-key -r 0EE7A126
+
{{Tip|Bootloaders with support for ZFS are described in [[#Install and configure the bootloader]].}}
    # pacman-key --lsign-key 0EE7A126
+
{{Warning|Several GRUB bugs ([https://savannah.gnu.org/bugs/?42861 bug #42861], [https://github.com/zfsonlinux/grub/issues/5 zfsonlinux/grub/issues/5]) complicate installing it on ZFS partitions, see [[#Install and configure the bootloader]] for a workaround}}
  
Finally, update the pacman databases,
+
=== Example parted commands ===
 +
Here are some example commands to partition a drive for the second scenario above ie using BIOS/legacy boot mode with a GPT partition table and a (slighty more than) 1MB BIOS boot partition for GRUB:
  
    # pacman -Syy
+
# parted /dev/sdx
 +
(parted)mklabel gpt
 +
(parted)mkpart non-fs 0% 2
 +
(parted)mkpart primary 2 100%
 +
(parted)set 1 bios_grub on
 +
(parted)set 2 boot on
 +
(parted)quit
  
==Install needed packages==
+
You can achieve the above in a single command like so:
  
This is also the best time to install your favorite text editor, otherwise nano will have to be used.
+
parted --script /dev/sdx mklabel gpt mkpart non-fs 0% 2 mkpart primary 2 100% set 1 bios_grub on set 2 boot on
  
    # pacman -S archzfs dosfstools gptfdisk vim
+
If you are creating an EFI partition then that should have the boot flag set instead of the root partition.
  
==Partition the destination drive==
+
== Format the destination disk ==
  
===UEFI systems===
+
If you have opted for a boot partition as well as any other non-ZFS system partitions then format them. Do not do anything to the Solaris partition nor to the BIOS boot partition. ZFS will manage the first, and your bootloader the second.
  
Use the cgdisk partition utility and create a GPT partition table:
+
== Setup the ZFS filesystem ==
  
  Part    Size  Type
+
First, make sure the ZFS modules are loaded,
  ====    =====  =============
+
      1    512M  EFI (ef00)
+
      2    512M  Ext4 (8200)
+
      2    XXXG  Solaris Root (bf00)
+
  
{{Note|The EFI partion will be formatted to FAT32 and contain the UEFI boot loader. The Ext4 partition will contain the boot partition and kernel images.}}
+
# modprobe zfs
  
{{Note|The filesystem type codes for cgdisk are indicated in the parenthesis after the filesystem name.}}
+
=== Create the root zpool ===
  
{{Warning|The EFI partition must be at least 512MB specified by the UEFI standard.}}
+
# zpool create -f zroot /dev/disk/by-id/''id-to-partition-partx''
  
===BIOS systems===
+
{{Warning|
 +
* Always use id names when working with ZFS, otherwise import errors will occur.
 +
* The zpool command will normally activate all features. See [[ZFS#GRUB-compatible pool creation]] when using [[GRUB]].}}
  
This section has not been written yet.
+
=== Create your datasets ===
  
==Format the destination disk==
+
Instead of using conventional disk partitions, ZFS has the concept of datasets to manage your storage. Unlike disk partitions, datasets have no fixed size and allow for different attributes, such as compression, to be applied per dataset. Normal ZFS datasets are mounted automatically by ZFS whilst legacy datasets are required to be mounted using fstab or with the traditional mount command.
  
===UEFI systems===
+
One of the most useful features of ZFS is boot environments. Boot environments allow you to create a bootable snapshot of your system that you can revert to at any time instantly by simply rebooting and booting from that boot environment. This can make doing system updates much safer and is also incredibly useful for developing and testing software. In order to be able to use [https://github.com/b333z/beadm beadm] to manage boot environments your datasets must be configured properly. Key to this are that you split your data directories (such as {{ic|/home}}) into datasets that are distinct from your system datasets and that you do not place data in the root of the pool as this cannot be moved afterwards.
  
Format the EFI partition to FAT32
+
You should always create a dataset for at least your root filesystem and in nearly all cases you will also want {{ic|/home}} to be in a separate dataset. You may decide you want your logs to persist over boot environments. If you are a running any software that stores data outside of {{ic|/home}} (such as is the case for database servers) you should structure your datasets so that the data directories of the software you want to run are separated out from the root dataset.
  
    mkfs.vfat -F 32 /dev/sda1 -n EFIBOOT
+
With these example commands, we will create a basic boot environment compatible configuration comprising of just root and {{ic|/home}} datasets with lz4 compression to save space and improve IO performance:
  
Format the Ext4 boot partition
+
# zfs create -o mountpoint=none zroot/data
 +
# zfs create -o mountpoint=none zroot/ROOT
 +
# zfs create -o compression=lz4 -o mountpoint=/ zroot/ROOT/default
 +
# zfs create -o compression=lz4 -o mountpoint=/home zroot/data/home
  
    mkfs.ext4 /dev/sda2 -L BOOT
+
=== Configure the root filesystem ===
  
===BIOS systems===
+
If you have just created your zpool, it will be mounted in a dir at the root of your tree named after the pool (ie /zroot). If the following set commands fail, you may need to unmount any ZFS filesystems first:
  
This section has not been written yet.
+
# zfs umount -a
  
==Setup the ZFS filesystem==
+
Now set the mount points of the datasets:
  
First, make sure the ZFS modules are loaded,
+
# zfs set mountpoint=/ zroot/ROOT/default
 +
# zfs set mountpoint=legacy zroot/data/home
  
    # modprobe zfs
+
{{Note|{{ic|/etc/fstab}} mounts occur before zfs mounts, so don't use zfs mountpoints on directories with subfolders configured to be mounted by {{ic|/etc/fstab}}.}}
  
===Create the root zpool===
+
and put them in {{ic|/etc/fstab}}
 +
{{hc|/etc/fstab|
 +
# <file system>        <dir>        <type>    <options>              <dump> <pass>
 +
zroot/ROOT/default / zfs defaults,noatime 0 0
 +
zroot/data/home /home zfs defaults,noatime 0 0}}
  
    # zpool create rpool /dev/disk/by-id/<id-to-partition>
+
All legacy datasets must be listed in {{ic|/etc/fstab}} or they will not be mounted at boot.
  
{{Warning|Always use id names when working with ZFS, otherwise import errors will occur.}}
+
Set the bootfs property on the descendant root filesystem so the boot loader knows where to find the operating system.
  
===Create the root filesystem===
+
# zpool set bootfs=zroot/ROOT/default zroot
  
    # zfs create rpool/ROOT
+
Export the pool,
  
create the descendant file system that will hold the installation:
+
# zpool export zroot
  
    # zfs create rpool/ROOT/arch
+
{{Warning|Do not skip this, otherwise you will be required to use {{ic|-f}} when importing your pools. This unloads the imported pool.}}
 +
{{Note|This might fail if you added a swap partition. You need to turn it off with the ''swapoff'' command.}}
  
We will set the mount points after we have created the filesystems so that they are not mounted automatically by ZFS.
+
Finally, re-import the pool,
  
If so desired, sub-filesystem mount points such as /home and /root can be created with the following commands:
+
# zpool import -d /dev/disk/by-id -R /mnt zroot
  
    # zfs create rpool/HOME
+
{{Note|{{ic|-d}} is not the actual device id, but the {{ic|/dev/by-id}} directory containing the symbolic links.
    # zfs create rpool/HOME/root
+
If this command fails and you are asked to import your pool via its numeric ID, run {{ic|zpool import}} to
 +
find out the ID of your pool then use a command such as:
 +
{{ic|zpool import 9876543212345678910 -R /mnt zroot}}
 +
}}
  
For safety, unmount all zfs filesystems if they are mounted:
+
If there is an error in this step, you can export the pool to redo the command. The ZFS filesystem is now ready to use.
  
    # zfs umount -a
+
Be sure to bring the {{ic|zpool.cache}} file into your new system. This is required later for the ZFS daemon to start.
  
===Configure the root filesystem===
+
# cp /etc/zfs/zpool.cache /mnt/etc/zfs/zpool.cache
  
Now it is time to set the mount point of the root filesystem:
+
if you do not have {{ic|/etc/zfs/zpool.cache}}, create it:
  
    # zfs set mountpoint=/ rpool/ROOT/arch
+
# zpool set cachefile=/etc/zfs/zpool.cache zroot
  
and optionally, any sub-filesystems:
+
== Install and configure Arch Linux ==
  
    # zfs set mountpoint=/home rpool/HOME
+
Follow the following steps using the [[Installation guide]]. It will be noted where special consideration must be taken for ZFSonLinux.
    # zfs set mountpoint=/root rpool/HOME/root
+
  
Set the bootfs property on the descendant root filesystem so the boot loader knows where to find the operating system.
+
* First mount any legacy or non-ZFS boot or system partitions using the mount command.
  
    # zpool set bootfs=rpool/ROOT/arch rpool
+
* Install the base system.
  
Export the pool,
+
* The procedure described in [[Installation guide#Fstab]] is usually overkill for ZFS. ZFS usually auto mounts its own partitions, so we do not need ZFS partitions in {{ic|fstab}} file, unless the user made legacy datasets of system directories. To generate the {{ic|fstab}} for filesystems, use:
  
    # zpool export rpool
+
# genfstab -U -p /mnt >> /mnt/etc/fstab
  
{{Warning|Don't skip this, otherwise you will be required to use -f when importing your pools. This unloads the imported pool.}}
+
* Edit the {{ic|/etc/fstab}}:
  
Finally, re-import the pool,
+
{{Note|
 +
* If you chose to create legacy datasets for system directories, keep them in this {{ic|fstab}}!
 +
* Comment out all non-legacy datasets apart from the root dataset, the swap file and the boot/EFI partition. It is a convention to replace the swap's uuid with {{ic|/dev/zvol/zroot/swap}}.
 +
}}
  
    # zpool import -d /dev/disk/by-id -R /mnt rpool
+
* You need to add the [[Unofficial_user_repositories#archzfs|Arch ZFS]] repository to {{ic|/etc/pacman.conf}}, sign its key and [[install]] '''zfs-linux''' (or '''zfs-linux-lts''' if you are running the LTS kernel) within the arch-chroot before you can update the ramdisk with ZFS support.
  
{{Note|"-d" is not the actual device id, but the /dev/by-id directory containing the symlinks.}}
+
* When creating the initial ramdisk, first edit {{ic|/etc/mkinitcpio.conf}} and add {{ic|zfs}} before filesystems. Also, move {{ic|keyboard}} hook before {{ic|zfs}} so you can type in console if something goes wrong. You may also remove fsck (if you are not using Ext3 or Ext4). Your {{ic|HOOKS}} line should look something like this:
 +
HOOKS="base udev autodetect modconf block keyboard zfs filesystems"
  
If there is an error in this step, you can export the pool to redo the command. The ZFS filesystem is now ready to use.
+
When using systemd in the initrd, you need to install {{AUR|mkinitcpio-sd-zfs}} and add the {{ic|sd-zfs}} hook after the {{ic|systemd}} hook instead of the {{ic|zfs}} hook. Keep in mind that this hook uses different kernel parameters than the default {{ic|zfs}} hook, more information can be found at the [https://github.com/dasJ/sd-zfs project page].
  
==Mount the boot partitions==
+
{{Note|
 
+
* If you are using a separate dataset for {{ic|/usr}} and have followed the instructions below, you must make sure you have the {{ic|usr}} hook enabled after {{ic|zfs}}, or your system will not boot.
===UEFI systems===
+
}}
 
+
    # mkdir /mnt/boot
+
    # mount /dev/sda2 /mnt/boot
+
    # mkdir /mnt/boot/efi
+
    # mount /dev/sda1 /mnt/boot/efi
+
 
+
===BIOS systems===
+
 
+
This section has not been written yet.
+
 
+
==Install and configure the Arch Linux installation==
+
 
+
Install the base packages,
+
 
+
    # pacstrap -i /mnt base base-devel archzfs sudo gnupg vim
+
 
+
Generate the fstab,
+
 
+
    # genfstab -U -p /mnt >> /mnt/etc/fstab
+
  
Open fstab to edit contents,
+
* [[Regenerate the initramfs]].
  
    # nano /mnt/etc/fstab
+
== Install and configure the bootloader ==
  
{{Note|Delete all the lines except for the boot partion. ZFS auto mounts its own partitions.}}
+
=== For BIOS motherboards ===
  
If installing on a UEFI system, you will need to load the efivars kernel module before chrooting into the installation:
+
Follow [[GRUB#BIOS systems]] to install GRUB onto your disk. {{ic|grub-mkconfig}} does not properly detect the ZFS filesystem, so it is necessary to edit {{ic|grub.cfg}} manually:
  
    # modprobe efivars
+
{{hc|/boot/grub/grub.cfg|<nowiki>
 +
set timeout=2
 +
set default=0
  
Chroot into the installation
+
# (0) Arch Linux
 +
menuentry "Arch Linux" {
 +
    linux /vmlinuz-linux zfs=zroot rw
 +
    initrd /initramfs-linux.img
 +
}
 +
</nowiki>}}
  
    # arch-chroot /mnt /bin/bash
+
if you did not create a separate /boot partition, kernel and initrd paths have to be in the following format:
  
Next, follow the [[Beginners' Guide]] from the "Locale" section to the "Configure Pacman Section". Once done, edit {{ic|pacman.conf}}, add the archzfs repository, and update the pacman database,
+
  /dataset/@/actual/path 
  
    # pacman -Syy
+
Example with Arch installed on the main dataset (not recommended - this will not allow for boot environments):
  
Re-create the initramfs, edit {{ic|/etc/mkinitcpio.conf}} and add {{ic|zfs}} before filesystems.  Remove fsck and then regenerate the initramfs:
+
    linux /@/boot/vmlinuz-linux zfs=zroot rw
 +
    initrd /@/boot/initramfs-linux.img
  
    # mkinitcpio -p linux
+
Example with Arch installed on a separate dataset zroot/ROOT/default:
  
Finally, set root password and add a regular user.
+
    linux /ROOT/default/@/boot/vmlinuz-linux zfs=zroot/ROOT/default rw
 +
    initrd /ROOT/default/@/boot/initramfs-linux.img
  
==Setup the bootloader==
+
When you come to installing GRUB, you are likely to get an error like:
  
===UEFI systems===
+
Failed to get canonical path of /dev/ata-yourdriveid-partx
  
Use EFISTUB and rEFInd for the UEFI boot loader. See [[Beginners' Guide#For UEFI motherboards]].  The kernel parameters in refind_linux.conf for zfs should include "zfs=bootfs", or "zfs=rpool/ROOT/arch", so the system can boot from ZFS.  The 'root' and 'rootfstype' parameters aren't needed.
+
Until this gets fixed, the easiest workaround is to create a symbolic link from the regular Linux device name of the partition to the device name GRUB is looking for:
  
===BIOS systems===
+
# ln -s /dev/sdax /dev/ata-yourdriveid-partx
  
This section has not been written yet.
+
=== For UEFI motherboards ===
  
==Unmount and restart==
+
Use {{ic|EFISTUB}} and {{ic|rEFInd}} for the UEFI boot loader. The kernel parameters in {{ic|refind_linux.conf}} for ZFS should include {{ic|1=zfs=bootfs}} or {{ic|1=zfs=zroot}} so the system can boot from ZFS. The {{ic|root}} and {{ic|rootfstype}} parameters are not needed.
  
This is it, we are done!
+
== Unmount and restart ==
  
    # exit
+
We are almost done!
    # umount /mnt/boot
+
# exit
    # zfs umount -a
+
# umount /mnt/boot (if you have a legacy boot partition)
    # zpool export rpool
+
# zfs umount -a
    # reboot
+
# zpool export zroot
 +
Now reboot.
  
 
{{Warning|If you do not properly export the zpool, the pool will refuse to import in the ramdisk environment and you will be stuck at the busybox terminal.}}
 
{{Warning|If you do not properly export the zpool, the pool will refuse to import in the ramdisk environment and you will be stuck at the busybox terminal.}}
  
==Troubleshooting==
+
== After the first boot ==
  
If the new installation does not boot because the zpool cannot be imported, you will need to chroot into the installation and properly export the zpool. See [[ZFS#Emergency chroot repair with archzfs]].
+
If everything went fine up to this point, your system will boot. Once.
 +
For your system to be able to reboot without issues, you need to enable the {{ic|zfs.target}} to auto mount the pools and set the hostid.
  
Once inside the chroot environment, load the ZFS module and force import the zpool,
+
For each pool you want automatically mounted execute:
 +
# zpool set cachefile=/etc/zfs/zpool.cache <pool>
 +
Enable the target with [[systemd]]:
 +
# systemctl enable zfs.target
  
    # zpool import -a -f
+
When running ZFS on root, the machine's hostid will not be available at the time of mounting the root filesystem. There are two solutions to this. You can either place your spl hostid in the [[kernel parameters]] in your boot loader. For example, adding {{ic|<nowiki>spl.spl_hostid=0x00bab10c</nowiki>}}, to get your number use the {{ic|hostid}} command.
  
now export the pool:
+
The other, and suggested, solution is to make sure that there is a hostid in {{ic|/etc/hostid}}, and then regenerate the initramfs image which will copy the hostid into the initramfs image. To write the hostid file safely you need to use a small C program:
  
    # zpool export <pool>
+
#include <stdio.h>
 +
#include <errno.h>
 +
#include <unistd.h>
 +
 +
int main() {
 +
    int res;
 +
    res = sethostid(gethostid());
 +
    if (res != 0) {
 +
        switch (errno) {
 +
            case EACCES:
 +
            fprintf(stderr, "Error! No permission to write the"
 +
                          " file used to store the host ID.\n"
 +
                          "Are you root?\n");
 +
            break;
 +
            case EPERM:
 +
            fprintf(stderr, "Error! The calling process's effective"
 +
                            " user or group ID is not the same as"
 +
                            " its corresponding real ID.\n");
 +
            break;
 +
            default:
 +
            fprintf(stderr, "Unknown error.\n");
 +
        }
 +
        return 1;
 +
    }
 +
    return 0;
 +
}
  
To see your available pools, use,
+
Copy it, save it as {{ic|writehostid.c}} and compile it with {{ic|gcc -o writehostid writehostid.c}}, finally execute it and regenerate the initramfs image:
  
    # zpool status
+
# ./writehostid
 +
# mkinitcpio -p linux
  
It is necessary to export a pool because of the way ZFS uses the hostid to track the system the zpool was created on. The hostid is generated partly based on your network setup. During the installation in the archiso your network configuration could be different generating a different hostid than the one contained in your new installation. Once the zfs filesystem is exported and then re-imported in the new installation, the hostid is reset. See [http://osdir.com/ml/zfs-discuss/2011-06/msg00227.html Re: Howto zpool import/export automatically? - msg#00227].
+
You can now delete the two files {{ic|writehostid.c}} and {{ic|writehostid}}. Your system should work and reboot properly now.
  
==See also==
+
== See also ==
  
 
* [https://github.com/dajhorn/pkg-zfs/wiki/HOWTO-install-Ubuntu-to-a-Native-ZFS-Root-Filesystem HOWTO install Ubuntu to a Native ZFS Root]
 
* [https://github.com/dajhorn/pkg-zfs/wiki/HOWTO-install-Ubuntu-to-a-Native-ZFS-Root-Filesystem HOWTO install Ubuntu to a Native ZFS Root]
* [http://lildude.co.uk/zfs-cheatsheet ZFS Cheatsheet]
+
* [http://lildude.co.uk/zfs-cheatsheet ZFS cheatsheet]
 +
* [http://www.funtoo.org/wiki/ZFS_Install_Guide Funtoo ZFS install guide]

Latest revision as of 10:10, 8 November 2016

This article details the steps required to install Arch Linux onto a ZFS root filesystem.

Installation

See ZFS#Installation for installing the ZFS packages. If installing Arch Linux onto ZFS from the archiso, it would be easier to use the archzfs repository.

Embedding archzfs into archiso

See ZFS article.

Arch ZFS installation scripts

Manually installing Arch using ZFS is quite an involved undertaking but thankfully there are scripts to simplify the process such as ALEZ and install-raidz.

Partition the destination drive

Review Partitioning for information on determining the partition table type to use for ZFS. ZFS supports GPT and MBR partition tables.

ZFS manages its own partitions, so only a basic partition table scheme is required. The partition that will contain the ZFS filesystem should be of the type bf00, or "Solaris Root".

When using GRUB as your bootloader with an MBR partition table there is no need for a BIOS boot partition. Drives larger than 2TB require a GPT partition table and you should use parted to create the partitions for GPT. BIOS/GPT and UEFI/GPT configurations require a small (1/2MB) BIOS boot partition to store the bootloader. If you are using a UEFI-only bootloader you should use GPT.

Depending upon your choice of bootloader you may or may not require an EFI partition. GRUB, when installed on a BIOS machine (or a UEFI machine booting in legacy mode) using either MBR or GPT doesn't require an EFI partition. Consult Boot loaders for more info.

Partition scheme

Here is an example of a basic partition scheme that could be employed for your ZFS root install on a BIOS/MBR installation using GRUB:

Part     Size   Type
----     ----   -------------------------
   1     XXXG   Solaris Root (bf00)

Using GRUB on a BIOS (or UEFI machine in legacy boot mode) machine but using a GPT partition table:

Part     Size   Type
----     ----   -------------------------
   1       2M   BIOS boot partition (ef02)
   2     XXXG   Solaris Root (bf00)

Another example, this time using a UEFI-specific bootloader (such as rEFInd) and GPT:

Part     Size   Type
----     ----   -------------------------
   1       2M   BIOS boot partition (ef02)
   2     100M   EFI boot partition (ef00)
   3     XXXG   Solaris Root (bf00)

ZFS does not support swap files. If you require a swap partition, see ZFS#Swap volume for creating a swap ZVOL.

Tip: Bootloaders with support for ZFS are described in #Install and configure the bootloader.
Warning: Several GRUB bugs (bug #42861, zfsonlinux/grub/issues/5) complicate installing it on ZFS partitions, see #Install and configure the bootloader for a workaround

Example parted commands

Here are some example commands to partition a drive for the second scenario above ie using BIOS/legacy boot mode with a GPT partition table and a (slighty more than) 1MB BIOS boot partition for GRUB:

# parted /dev/sdx
(parted)mklabel gpt
(parted)mkpart non-fs 0% 2
(parted)mkpart primary 2 100%
(parted)set 1 bios_grub on
(parted)set 2 boot on
(parted)quit

You can achieve the above in a single command like so:

parted --script /dev/sdx mklabel gpt mkpart non-fs 0% 2 mkpart primary 2 100% set 1 bios_grub on set 2 boot on

If you are creating an EFI partition then that should have the boot flag set instead of the root partition.

Format the destination disk

If you have opted for a boot partition as well as any other non-ZFS system partitions then format them. Do not do anything to the Solaris partition nor to the BIOS boot partition. ZFS will manage the first, and your bootloader the second.

Setup the ZFS filesystem

First, make sure the ZFS modules are loaded,

# modprobe zfs

Create the root zpool

# zpool create -f zroot /dev/disk/by-id/id-to-partition-partx
Warning:
  • Always use id names when working with ZFS, otherwise import errors will occur.
  • The zpool command will normally activate all features. See ZFS#GRUB-compatible pool creation when using GRUB.

Create your datasets

Instead of using conventional disk partitions, ZFS has the concept of datasets to manage your storage. Unlike disk partitions, datasets have no fixed size and allow for different attributes, such as compression, to be applied per dataset. Normal ZFS datasets are mounted automatically by ZFS whilst legacy datasets are required to be mounted using fstab or with the traditional mount command.

One of the most useful features of ZFS is boot environments. Boot environments allow you to create a bootable snapshot of your system that you can revert to at any time instantly by simply rebooting and booting from that boot environment. This can make doing system updates much safer and is also incredibly useful for developing and testing software. In order to be able to use beadm to manage boot environments your datasets must be configured properly. Key to this are that you split your data directories (such as /home) into datasets that are distinct from your system datasets and that you do not place data in the root of the pool as this cannot be moved afterwards.

You should always create a dataset for at least your root filesystem and in nearly all cases you will also want /home to be in a separate dataset. You may decide you want your logs to persist over boot environments. If you are a running any software that stores data outside of /home (such as is the case for database servers) you should structure your datasets so that the data directories of the software you want to run are separated out from the root dataset.

With these example commands, we will create a basic boot environment compatible configuration comprising of just root and /home datasets with lz4 compression to save space and improve IO performance:

# zfs create -o mountpoint=none zroot/data
# zfs create -o mountpoint=none zroot/ROOT
# zfs create -o compression=lz4 -o mountpoint=/ zroot/ROOT/default
# zfs create -o compression=lz4 -o mountpoint=/home zroot/data/home

Configure the root filesystem

If you have just created your zpool, it will be mounted in a dir at the root of your tree named after the pool (ie /zroot). If the following set commands fail, you may need to unmount any ZFS filesystems first:

# zfs umount -a

Now set the mount points of the datasets:

# zfs set mountpoint=/ zroot/ROOT/default
# zfs set mountpoint=legacy zroot/data/home
Note: /etc/fstab mounts occur before zfs mounts, so don't use zfs mountpoints on directories with subfolders configured to be mounted by /etc/fstab.

and put them in /etc/fstab

/etc/fstab
# <file system>        <dir>         <type>    <options>              <dump> <pass>
zroot/ROOT/default / zfs defaults,noatime 0 0
zroot/data/home /home zfs defaults,noatime 0 0

All legacy datasets must be listed in /etc/fstab or they will not be mounted at boot.

Set the bootfs property on the descendant root filesystem so the boot loader knows where to find the operating system.

# zpool set bootfs=zroot/ROOT/default zroot

Export the pool,

# zpool export zroot
Warning: Do not skip this, otherwise you will be required to use -f when importing your pools. This unloads the imported pool.
Note: This might fail if you added a swap partition. You need to turn it off with the swapoff command.

Finally, re-import the pool,

# zpool import -d /dev/disk/by-id -R /mnt zroot
Note: -d is not the actual device id, but the /dev/by-id directory containing the symbolic links.

If this command fails and you are asked to import your pool via its numeric ID, run zpool import to find out the ID of your pool then use a command such as: zpool import 9876543212345678910 -R /mnt zroot

If there is an error in this step, you can export the pool to redo the command. The ZFS filesystem is now ready to use.

Be sure to bring the zpool.cache file into your new system. This is required later for the ZFS daemon to start.

# cp /etc/zfs/zpool.cache /mnt/etc/zfs/zpool.cache

if you do not have /etc/zfs/zpool.cache, create it:

# zpool set cachefile=/etc/zfs/zpool.cache zroot

Install and configure Arch Linux

Follow the following steps using the Installation guide. It will be noted where special consideration must be taken for ZFSonLinux.

  • First mount any legacy or non-ZFS boot or system partitions using the mount command.
  • Install the base system.
  • The procedure described in Installation guide#Fstab is usually overkill for ZFS. ZFS usually auto mounts its own partitions, so we do not need ZFS partitions in fstab file, unless the user made legacy datasets of system directories. To generate the fstab for filesystems, use:
# genfstab -U -p /mnt >> /mnt/etc/fstab
  • Edit the /etc/fstab:
Note:
  • If you chose to create legacy datasets for system directories, keep them in this fstab!
  • Comment out all non-legacy datasets apart from the root dataset, the swap file and the boot/EFI partition. It is a convention to replace the swap's uuid with /dev/zvol/zroot/swap.
  • You need to add the Arch ZFS repository to /etc/pacman.conf, sign its key and install zfs-linux (or zfs-linux-lts if you are running the LTS kernel) within the arch-chroot before you can update the ramdisk with ZFS support.
  • When creating the initial ramdisk, first edit /etc/mkinitcpio.conf and add zfs before filesystems. Also, move keyboard hook before zfs so you can type in console if something goes wrong. You may also remove fsck (if you are not using Ext3 or Ext4). Your HOOKS line should look something like this:
HOOKS="base udev autodetect modconf block keyboard zfs filesystems"

When using systemd in the initrd, you need to install mkinitcpio-sd-zfsAUR and add the sd-zfs hook after the systemd hook instead of the zfs hook. Keep in mind that this hook uses different kernel parameters than the default zfs hook, more information can be found at the project page.

Note:
  • If you are using a separate dataset for /usr and have followed the instructions below, you must make sure you have the usr hook enabled after zfs, or your system will not boot.

Install and configure the bootloader

For BIOS motherboards

Follow GRUB#BIOS systems to install GRUB onto your disk. grub-mkconfig does not properly detect the ZFS filesystem, so it is necessary to edit grub.cfg manually:

/boot/grub/grub.cfg
set timeout=2
set default=0

# (0) Arch Linux
menuentry "Arch Linux" {
    linux /vmlinuz-linux zfs=zroot rw
    initrd /initramfs-linux.img
}

if you did not create a separate /boot partition, kernel and initrd paths have to be in the following format:

 /dataset/@/actual/path  

Example with Arch installed on the main dataset (not recommended - this will not allow for boot environments):

   linux /@/boot/vmlinuz-linux zfs=zroot rw
   initrd /@/boot/initramfs-linux.img

Example with Arch installed on a separate dataset zroot/ROOT/default:

   linux /ROOT/default/@/boot/vmlinuz-linux zfs=zroot/ROOT/default rw 
   initrd /ROOT/default/@/boot/initramfs-linux.img

When you come to installing GRUB, you are likely to get an error like:

Failed to get canonical path of /dev/ata-yourdriveid-partx

Until this gets fixed, the easiest workaround is to create a symbolic link from the regular Linux device name of the partition to the device name GRUB is looking for:

# ln -s /dev/sdax /dev/ata-yourdriveid-partx

For UEFI motherboards

Use EFISTUB and rEFInd for the UEFI boot loader. The kernel parameters in refind_linux.conf for ZFS should include zfs=bootfs or zfs=zroot so the system can boot from ZFS. The root and rootfstype parameters are not needed.

Unmount and restart

We are almost done!

# exit
# umount /mnt/boot (if you have a legacy boot partition)
# zfs umount -a
# zpool export zroot

Now reboot.

Warning: If you do not properly export the zpool, the pool will refuse to import in the ramdisk environment and you will be stuck at the busybox terminal.

After the first boot

If everything went fine up to this point, your system will boot. Once. For your system to be able to reboot without issues, you need to enable the zfs.target to auto mount the pools and set the hostid.

For each pool you want automatically mounted execute:

# zpool set cachefile=/etc/zfs/zpool.cache <pool>

Enable the target with systemd:

# systemctl enable zfs.target

When running ZFS on root, the machine's hostid will not be available at the time of mounting the root filesystem. There are two solutions to this. You can either place your spl hostid in the kernel parameters in your boot loader. For example, adding spl.spl_hostid=0x00bab10c, to get your number use the hostid command.

The other, and suggested, solution is to make sure that there is a hostid in /etc/hostid, and then regenerate the initramfs image which will copy the hostid into the initramfs image. To write the hostid file safely you need to use a small C program:

#include <stdio.h>
#include <errno.h>
#include <unistd.h>

int main() {
    int res;
    res = sethostid(gethostid());
    if (res != 0) {
        switch (errno) {
            case EACCES:
            fprintf(stderr, "Error! No permission to write the"
                         " file used to store the host ID.\n"
                         "Are you root?\n");
            break;
            case EPERM:
            fprintf(stderr, "Error! The calling process's effective"
                            " user or group ID is not the same as"
                            " its corresponding real ID.\n");
            break;
            default:
            fprintf(stderr, "Unknown error.\n");
        }
        return 1;
    }
    return 0;
}

Copy it, save it as writehostid.c and compile it with gcc -o writehostid writehostid.c, finally execute it and regenerate the initramfs image:

# ./writehostid
# mkinitcpio -p linux

You can now delete the two files writehostid.c and writehostid. Your system should work and reboot properly now.

See also