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Feel free to leave comments. --[[User:Indigo|Indigo]] ([[User talk:Indigo|talk]]) 17:43, 27 September 2012 (UTC)
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) ==
== Encrypting a LVM setup ==
{{Merge|Encrypted_LVM |Device mapper stacking is explained there building on the LVM wiki with a howto for both approaches below.}}
It's really easy to use encryption with [[LVM]]. 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.
'''LVM on LUKS'''
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 LUKS blockdevice. Hence, the LVM is not transparent until the blockdevice is unlocked and the underlying volume structure is scanned and mounted during boot.
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}}.
'''LUKS on LVM'''
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.
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.
=== LVM with Arch Linux Installer (>2009.08 <2012.07.15) ===
{{Out of date|As of the [https://www.archlinux.org/news/install-media-20120715-released/ 2012.07.15 installation media release] the AIF (Arch Installation Framework) and grub-legacy are dropped. These outdated instructions still give the backbones to understanding what to do. If you plan to do a fresh install, also check the howto [[Encrypted_LVM]].}}
In between Arch Linux installation media release 2009.08 and 2012.07.15 LVM and dm_crypt had been supported by the installer out of the box.
This made it very easy to configure a system for [[LVM]] on dm-crypt or vice versa.
Actually the configuration is done exactly as without LVM: see the [[#Arch Linux Installer (>2009.08 <2012.07.15)|corresponding]] section above. It differs only in two aspects.
==== The partition and filesystem choice ====
Create a small, unencrypted boot partition and use the remaining space for a single partition which can later be split up into multiple logic volumes by [[LVM]].
For a LVM-on-dm-crypt system set up the filesystems and mounting points for example like this:
/dev/sda1  raw->ext2;yes;/boot;no_opts;no_label;no_params
/dev/sda2  raw->dm_crypt;yes;no_mountpoint;no_opts;sda2crypt;-c_aes-xts-plain_-y_-s_512
/dev/mapper/sda2crypt  dm_crypt->lvm-vg;yes;no_mountpoint;no_opts;no_label;no_params
/dev/mapper/sda2crypt+  lvm-pv->lvm-vg;yes;no_mountpoint;no_opts;cryptpool;no_params
/dev/mapper/cryptpool  lvm-vg(cryptpool)->lvm-lv;yes;no_mountpoint;no_opts;cryptroot;10000M|lvm-lv;yes;no_mountpoint;no_opts;crypthome;20000M
/dev/mapper/cryptpool-cryptroot  lvm-lv(cryptroot)->ext3;yes;/;no_opts;cryptroot;no_params
/dev/mapper/cryptpool-crypthome  lvm-lv(crypthome)->ext3;yes;/home;no_opts;cryptroot;no_params
==== The configuration stage ====
* In {{ic|/etc/mkinitcpio.conf}} add the {{ic|encrypt}} hook '''before''' the {{ic|lvm2}} hook in the {{ic|HOOKS}} array, if you set up LVM on top of the encrypted partition.
That is it for the LVM & dm_crypt specific part. The rest is done as usual.
=== Applying this to a non-root partition ===
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.
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).
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.
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
kernel /boot/vmlinuz-linux md=1,/dev/hda5,/dev/hdb5
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:
kernel /boot/vmlinuz-linux root=/dev/md0 ro md=0,/dev/sda1,/dev/sdb1 md=1,/dev/sda5,/dev/sdb5,/dev/sdc5
=== LVM and dm-crypt manually (short version) ===
==== Notes ====
If you are smart enough for this, you will be smart enough to ignore/replace LVM-specific things.
{{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.}}
==== Partitioning scheme ====
{{ic|/dev/sda1}} -> {{ic|/boot}}
{{ic|/dev/sda2}} -> LVM
==== The commands ====
cryptsetup -d /dev/random -c aes-xts-plain -s 512 create lvm /dev/sda2
dd if=/dev/urandom of=/dev/mapper/lvm
cryptsetup remove lvm
lvm pvcreate /dev/sda2
lvm vgcreate lvm /dev/sda2
lvm lvcreate -L 10G -n root lvm
lvm lvcreate -L 500M -n swap lvm
lvm lvcreate -L 500M -n tmp lvm
lvm lvcreate -l 100%FREE -n home lvm
cryptsetup luksFormat -c aes-xts-plain -s 512 /dev/lvm/root
cryptsetup luksOpen /dev/lvm/root root
mkreiserfs /dev/mapper/root
mount /dev/mapper/root /mnt
dd if=/dev/zero of=/dev/sda1 bs=1M
mkreiserfs /dev/sda1
mkdir /mnt/boot
mount /dev/sda1 /mnt/boot
mkdir -p -m 700 /mnt/etc/luks-keys
dd if=/dev/random of=/mnt/etc/luks-keys/home bs=1 count=256
==== Install Arch Linux ====
Run {{ic|/arch/setup}}
==== Configuration ====
===== /etc/rc.conf =====
Change {{ic|USELVM<nowiki>=</nowiki>"no"}} to {{ic|USELVM<nowiki>=</nowiki>"yes"}}.
===== /etc/mkinitcpio.conf =====
Put {{ic|lvm2}} and {{ic|encrypt}} (in that order) before {{ic|filesystems}} in the {{ic|HOOKS}} array. Again, note that you are setting encryption on '''top''' of LVM.)
if you want install the system on a usb stick, you need to put {{ic|usb}} just after {{ic|udev}}.
===== /boot/grub/menu.lst =====
Change {{ic|root<nowiki>=</nowiki>/dev/hda3}} to {{ic|root<nowiki>=</nowiki>/dev/lvm/root}}.
For kernel >= 2.6.30, you should change {{ic|root<nowiki>=</nowiki>/dev/hda3}} to the following:
cryptdevice=/dev/lvm/root:root root=/dev/mapper/root
if you want install the system on a usb stick, you need to add {{ic|lvmdelay<nowiki>=</nowiki>/dev/mapper/lvm-root}}
===== /etc/fstab =====
/dev/mapper/root        /      reiserfs        defaults        0      1
/dev/sda1              /boot  reiserfs        defaults        0      2
/dev/mapper/tmp        /tmp    tmpfs          defaults        0      0
/dev/mapper/swap        none    swap            sw              0      0
===== /etc/crypttab =====
swap /dev/lvm/swap SWAP -c aes-xts-plain -h whirlpool -s 512
tmp /dev/lvm/tmp /dev/urandom -c aes-xts-plain -s 512
==== After rebooting ====
===== The commands =====
cryptsetup luksFormat -c aes-xts-plain -s 512 /dev/lvm/home /etc/luks-keys/home
cryptsetup luksOpen -d /etc/luks-keys/home /dev/lvm/home home
mkreiserfs /dev/mapper/home
mount /dev/mapper/home /home
===== /etc/crypttab =====
home /dev/lvm/home  /etc/luks-keys/home
===== /etc/fstab =====
/dev/mapper/home        /home  reiserfs        defaults        0      0
=== / on LVM on LUKS ===
Make sure your kernel command line looks like this:
root=/dev/mapper/<volume-group>-<logical-volume> cryptdevice=/dev/<luks-part>:<volume-group>
For example:
root=/dev/mapper/vg-arch cryptdevice=/dev/sda4:vg
Or like this:
cryptdevice=/dev/<volume-group>/<logical-volume>:root root=/dev/mapper/root
==saving links for resources section==
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]

Revision as of 13:38, 21 July 2013

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