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Feel free to leave comments. --[[User:Indigo|Indigo]] ([[User talk:Indigo|talk]]) 17:43, 27 September 2012 (UTC)
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Feel free to leave comments about my wiki edits or other points of interest. --[[User:Indigo|Indigo]] ([[User talk:Indigo|talk]]) 17:43, 27 September 2012 (UTC)
  
== Encrypting a LVM setup (rework of LUKS section 8) ==
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====Comments====
 
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== Encrypting a LVM setup ==
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{{Merge|Encrypted_LVM |Device mapper stacking is explained there building on the LVM wiki with a howto for both approaches below.}}
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It is easy to use encryption with [[LVM]]. This section describes specific aspects of setting up an encrypted LVM setup and mini-howto's for users with experiences of using both, cryptsetup and LVM. If you are looking for verbose installation instructions of such a setup, you might want to read [[Encrypted_LVM]] first.
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If you do not know how to set up LVM, then read [[Installing with Software RAID or LVM]]. Using LVM is particularly helpful when a system with multiple partitions is planned. While there are a number of alternatives for unlocking multiple partitions with the same passphrase/key, the default Arch initcpio hooks do not implement non-standard ways. A combination of the initcpio {{ic|encrypt}} and {{ic|lvm2}} hooks, however, enables to setup a system with numerous logical volumes as partitions while using one passphrase/key to unlock them.
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'''LVM on LUKS'''
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The straight-forward method is to set up LVM on top of the encrypted partition instead of the other way round. Technically the LVM is setup inside one big encrypted blockdevice. Hence, the LVM is not transparent until the blockdevice is unlocked and the underlying volume structure is scanned and mounted during boot.
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The most important thing in setting LVM on '''top''' of encryption is to [[#Configure initramfs|configure the initramfs]] for running '''both''' the {{ic|encrypt}} hook '''and''' the {{ic|lvm2}} hook (and those two before the {{ic|filesystems}} hook). In the past, it was necessary to ensure the correct ordering of these hooks in {{ic|/etc/mkinitcpio.conf}} but the order no longer matters with the current implementation of {{ic|lvm2}}.
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'''LUKS on LVM'''
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To use encryption on top of LVM, you have to first set up your LVM volumes and then use them as the base for the encrypted partitions. That means, in short, that you have to set up LVM first. Then follow this guide, but replace all occurrences of {{ic|/dev/sdXy}} in the guide with its LVM counterpart. (E.g.: {{ic|/dev/sda5}} -> {{ic|/dev/<volume group name>/home}}). This is used to setup partitions (inside the LVM) which can be unlocked separately or a mixture of encrypted and non-encrypted partitions.
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For encrypted partitions inside an LVM, the LVM-hook has to run first, before the respective encrypted logical volumes can be unlocked. So for this add the {{ic|encrypt}} hook in {{ic|/etc/mkinitcpio.conf}} '''after''' the {{ic|lvm2}} hook, if you chose to set up encrypted partitions on '''top''' of LVM.
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Both these options are described in more detail in [[Encrypted_LVM]].
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=== Applying this to a non-root partition ===
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You might get tempted to apply all this fancy stuff to a non-root partition. Arch does not support this out of the box, however, you can easily change the cryptdev and cryptname values in {{ic|/lib/initcpio/hooks/encrypt}} (the first one to your {{ic|/dev/sd*}} partition, the second to the name you want to attribute). That should be enough.
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The big advantage is you can have everything automated, while setting up {{ic|/etc/crypttab}} with an external key file (i.e. the keyfile is not on any internal hard drive partition) can be a pain - you need to make sure the USB/FireWire/... device gets mounted before the encrypted partition, which means you have to change the order of {{ic|/etc/fstab}} (at least).
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Of course, if the {{pkg|cryptsetup}} package gets upgraded, you will have to change this script again. Unlike {{ic|/etc/crypttab}}, only one partition is supported, but with some further hacking one should be able to have multiple partitions unlocked.
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If you want to do this on a software RAID partition, there is one more thing you need to do. Just setting the {{ic|/dev/mdX}} device in {{ic|/lib/initcpio/hooks/encrypt}} is not enough; the {{ic|encrypt}} hook will fail to find the key for some reason, and not prompt for a passphrase either. It looks like the RAID devices are not brought up until after the {{ic|encrypt}} hook is run. You can solve this by putting the RAID array in {{ic|/boot/grub/menu.lst}}, like
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kernel /boot/vmlinuz-linux md=1,/dev/hda5,/dev/hdb5
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If you set up your root partition as a RAID, you will notice the similarities with that setup ;-). [[GRUB]] can handle multiple array definitions just fine:
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kernel /boot/vmlinuz-linux root=/dev/md0 ro md=0,/dev/sda1,/dev/sdb1 md=1,/dev/sda5,/dev/sdb5,/dev/sdc5
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=== LVM and dm-crypt manually (short version) ===
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==== Notes ====
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If you are experienced with LVM, you will be able to ignore/replace LVM-specific things according to your plan.
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{{Note|This brief uses reiserfs for some of the partitions, so change this accordingly if you want to use a more "normal" file system, like ext4.}}
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==== Partitioning scheme ====
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{{ic|/dev/sda1}} -> {{ic|/boot}}
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{{ic|/dev/sda2}} -> LVM
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==== The commands ====
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cryptsetup -d /dev/random -c aes-xts-plain -s 512 create lvm /dev/sda2
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dd if=/dev/urandom of=/dev/mapper/lvm
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cryptsetup remove lvm
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lvm pvcreate /dev/sda2
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lvm vgcreate lvm /dev/sda2
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lvm lvcreate -L 10G -n root lvm
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lvm lvcreate -L 500M -n swap lvm
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lvm lvcreate -L 500M -n tmp lvm
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lvm lvcreate -l 100%FREE -n home lvm
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cryptsetup luksFormat -c aes-xts-plain -s 512 /dev/lvm/root
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cryptsetup luksOpen /dev/lvm/root root
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mkreiserfs /dev/mapper/root
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mount /dev/mapper/root /mnt
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dd if=/dev/zero of=/dev/sda1 bs=1M
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mkreiserfs /dev/sda1
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mkdir /mnt/boot
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mount /dev/sda1 /mnt/boot
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mkdir -p -m 700 /mnt/etc/luks-keys
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dd if=/dev/random of=/mnt/etc/luks-keys/home bs=1 count=256
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==== Install Arch Linux ====
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Run {{ic|/arch/setup}}
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==== Configuration ====
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===== /etc/mkinitcpio.conf =====
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Put {{ic|lvm2}} and {{ic|encrypt}} before {{ic|filesystems}} in the {{ic|HOOKS}} array. Again, note that you are setting encryption on '''top''' of LVM.)
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If you want install the system on a usb stick, you need to put {{ic|usb}} just after {{ic|udev}}.
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===== /boot/grub/grub.cfg =====
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Change {{ic|root<nowiki>=</nowiki>/dev/hda3}} to {{ic|root<nowiki>=</nowiki>/dev/lvm/root}}.
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For kernel >= 2.6.30, you should change {{ic|root<nowiki>=</nowiki>/dev/hda3}} to the following:
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cryptdevice=/dev/lvm/root:root root=/dev/mapper/root
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if you want install the system on a usb stick, you need to add {{ic|lvmdelay<nowiki>=</nowiki>/dev/mapper/lvm-root}}
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===== /etc/fstab =====
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/dev/mapper/root        /      reiserfs        defaults        0      1
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/dev/sda1              /boot  reiserfs        defaults        0      2
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/dev/mapper/tmp        /tmp    tmpfs          defaults        0      0
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/dev/mapper/swap        none    swap            sw              0      0
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===== /etc/crypttab =====
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swap /dev/lvm/swap SWAP -c aes-xts-plain -h whirlpool -s 512
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tmp /dev/lvm/tmp /dev/urandom -c aes-xts-plain -s 512
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==== After rebooting ====
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===== The commands =====
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cryptsetup luksFormat -c aes-xts-plain -s 512 /dev/lvm/home /etc/luks-keys/home
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cryptsetup luksOpen -d /etc/luks-keys/home /dev/lvm/home home
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mkreiserfs /dev/mapper/home
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mount /dev/mapper/home /home
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===== /etc/crypttab =====
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home /dev/lvm/home  /etc/luks-keys/home
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===== /etc/fstab =====
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/dev/mapper/home        /home  reiserfs        defaults        0      0
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=== / on LVM on LUKS ===
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Make sure your kernel command line looks like this:
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root=/dev/mapper/<volume-group>-<logical-volume> cryptdevice=/dev/<luks-part>:<volume-group>
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For example:
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root=/dev/mapper/vg-arch cryptdevice=/dev/sda4:vg
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Or like this:
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cryptdevice=/dev/<volume-group>/<logical-volume>:root root=/dev/mapper/root
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==saving links for resources section==
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This link here is easy to follow and explains everything: [http://www.pindarsign.de/webblog/?p=767 Arch Linux: LVM on top of an encrypted partition]
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Revision as of 22:33, 13 August 2013

Feel free to leave comments about my wiki edits or other points of interest. --Indigo (talk) 17:43, 27 September 2012 (UTC)

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