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Rootfs over encrypted lvm
This howto describes how to setup LVM and rootfs with cryptoLUKS-encrypted drive. It is not meant to be a standalone installation guide, rather, it is meant to be read alongside the Funtoo Linux Installation Guide.
Prepare the hard drive and partitions
prepare your drive following the official install guides GPT partitioning. Install/GPT_Partitioning
Encrypting the drive
Read more about different cipher options here: [1]
root # cryptsetup luksFormat /dev/sda3
Or use SHA512 for increase security. Do NOT use SHA-1: LUKS disk encryption. As the cryptography expert Bruce Schneier already told in year 2005, do not use SHA-1 because its broken. See his article here: [2]
root # cryptsetup --cipher twofish-xts-plain64 --hash sha512 --key-size 256 luksFormat /dev/sda3
Support for twofish-xts-plain64 is NOT in the default debian-kernel. You will need to configure and compile your own kernel if you choose this.
Initializes the volume
Initializes the volume, and sets an initial key or passphrase:
root # cryptsetup luksOpen /dev/sda3 dmcrypt_root
There you'll be prompted to enter your password phrase for encrypted drive, type your paranoid password there.
The default keymap at boot time is us. If you enter your passphrase using a different keymap, you won't be able to unlock your crypt volume if the passphrase contains any characters that are located elsewere on your keyboard layout that with the us layout.
Create logical volumes
root # pvcreate /dev/mapper/dmcrypt_root root # vgcreate vg /dev/mapper/dmcrypt_root root # lvcreate -L2G --name swap vg root # lvcreate -l 100%FREE --name root vg
Feel free to specify your desired size by altering the numbers after the -L flag. For example, to make your portage dataset 20GB's, use the flag -L20G instead of -L5G.
Please, notice that above mentioned partitioning scheme is an example and not a default recommendation, change it accordingly to desired scheme.
Create a filesystem on volumes
root # mkfs.vfat /dev/sdc2 root # mkswap /dev/mapper/vg-swap root # mkfs.ext4 /dev/mapper/vg-root
Basic system setup
root # swapon /dev/mapper/vg-swap root # mkdir /mnt/funtoo root # mount /dev/mapper/vg-root /mnt/funtoo root # mkdir /mnt/funtoo/boot root # mount /dev/sdc2 /mnt/funtoo/boot
Now perform all the steps required for basic system install, please follow the Funtoo Linux Installation Guide, but don't forget to emerge the following before your install is finished:
- cryptsetup
- lvm2
- a bootloader (grub recommended)
- kernel sources
Editing the fstab
Fire up your favorite text editor to edit /etc/fstab. You want to put the following in the file:
/etc/fstab # <fs> <mountpoint> <type> <opts> <dump/pass>
/dev/sda1 /boot ext2 noauto,noatime 1 2
/dev/mapper/vg-swap none swap sw 0 0
/dev/mapper/vg-root / ext4 noatime,nodiratime,defaults 0 1
/dev/sr0 /mnt/cdrom auto noauto,ro 0 0
/dev/mapper/vg-portage /usr/portage ext4 noatime,nodiratime 0 0
/dev/mapper/vg-home /home ext4 noatime,nodiratime 0 0
Kernel options
This part is particularly important: pay close attention.
Note: If you are using debian-sources as included in mid-May 2015 and later Funtoo stages, you do not need to rebuild the kernel. The following instructions are for other kernels that you may choose to install.
General setup --->
[*] Initial RAM filesystem and RAM disk (initramfs/initrd) support
Device Drivers --->
Generic Driver Options --->
[*] Maintain a devtmpfs filesystem to mount at /dev
Device Drivers --->
[*] Multiple devices driver support --->
<*>Device Mapper Support
<*> Crypt target support
Cryptographic API --->
<*> XTS support
-*-AES cipher algorithms
Initramfs setup and configuration
Better-initramfs
As of August 2016, better-initramfs is not required with debian-sources as included in current Funtoo stages. Unless you are doing something not with debian-sources as comes with the Funtoo stage, you can safely skip to the section on editing /etc/boot.conf.
Build your initramfs with better-initramfs project.
better-initramfs supports neither dynamic modules nor udev, so you should compile your kernel with built-in support for your block devices and file system support.
root # cd /opt root # git clone https://bitbucket.org/piotrkarbowski/better-initramfs.git root # cd better-initramfs root # less README.rst root # bootstrap/bootstrap-all root # make prepare root # make image
Copy resulting initramfs.cpio.gz to /boot:
root # cp output/initramfs.cpio.gz /boot
Alternatively, a pre-compiled binary initramfs is available at https://bitbucket.org/piotrkarbowski/better-initramfs/downloads
root # wget https://bitbucket.org/piotrkarbowski/better-initramfs/downloads/release-x86_64-v0.7.2.tar.bz2 root # tar xf release-x86_64-v0.5.tar.bz2 root # cd release* root # gzip initramfs.cpio root # cp initramfs.cpio.gz /boot
Remember, better-initramfs project is a work in progress, so you need to update from time to time. It can be done easily with git. Go to the better-initramfs source dir and follow:
root # cd /opt/better-initramfs root # git pull root # less ChangeLog
Please read the ChangeLog carefuly and perform necessary updates to /etc/boot.conf. Also, please backup the working /boot/initramfs.cpio.gz and /etc/boot.conf before updating better-initramfs.
Alternatively and much faster is to install better-initramfs-bin package, recently added to Funtoo's portage tree:
root # emerge better-initramfs-bin
Genkernel
Funtoo's genkernel capable to create initramfs for encrypted drive. Compile and install kernel and initramfs of your favorite kernel sources:
root # genkernel --kernel-config=/path/to/your/custom-kernel-config --no-mrproper --makeopts=-j5 --install --lvm --luks all
Bootloader Configuration
Grub2 configuration
Emerge Grub2 with device-mapper support
root # echo 'sys-boot/grub device-mapper' >> /etc/portage/package.use/grub root # emerge grub
better-initramfs
An example /etc/boot.conf for better-initramfs:
boot {
generate grub
default "Funtoo Linux"
timeout 3
}
"Funtoo Linux" {
kernel vmlinuz[-v]
initrd /initramfs.cpio.gz
params += enc_root=/dev/sda3 lvm luks root=/dev/mapper/vg-root rootfstype=ext4 resume=swap:/dev/mapper/vg-swap quiet
}
Now, run boot-update to write the configuration files to /boot/grub/grub.cfg
genkernel
Configure the bootloader as described above, with correct kernel and initramfs images names. An example for genkernel and grub2. You will be editing /etc/boot.conf:
boot {
generate grub
default "Funtoo Linux"
timeout 3
}
"Funtoo Linux" {
kernel kernel-genkernel-x86_64-3.13.0
initrd initramfs-genkernel-x86_64-3.13.0
params += crypt_root=/dev/sda3 dolvm real_root=/dev/mapper/vg-root rootfstype=ext4 resume=swap:/dev/mapper/vg-swap quiet
}
Lilo configuration
For oldschool geeks, an example for lilo bootloader. Emerge lilo with device-mapper support
root # echo 'sys-boot/lilo device-mapper' >> /etc/portage/package.use/lilo root # emerge lilo
Example /etc/lilo.conf for genkernel:
append="init=/linuxrc dolvm crypt_root=/dev/sda2 real_root=/dev/mapper/vg-root" boot=/dev/sda compact default=funtoo lba32 prompt read-only timeout=50 image=/boot/kernel-genkernel-x86_64-3.13.0 initrd=/boot/initramfs-genkernel-x86_64-3.13.0 label=funtoo
Syslinux bootloader setup
Syslinux is another advanced bootloader which you can find on all live CD's. Syslinux bootloader does not require additional BIOS boot partition. /dev/sda2 is the root partition.
root # emerge syslinux root # mkdir /boot/extlinux root # extlinux --install /boot/extlinux root # dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/mbr.bin of=/dev/sda - or - root # sgdisk /dev/sda --attributes=1:set:2 root # dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/gptmbr.bin of=/dev/sda, for GPT partition
Example /boot/extlinux/extlinux.conf for better-initramfs:
LABEL kernel1_bzImage-3.2.1 MENU LABEL Funtoo Linux bzImage-3.2.1 LINUX /bzImage-3.2.1 INITRD /initramfs.cpio.gz APPEND rootfstype=ext4 luks enc_root=/dev/sda2 lvm root=/dev/mapper/vg-root
Final steps
Umount everything, close encrypted drive and reboot
root # umount -l -v /mnt/funtoo/{dev, proc, home, usr/portage, boot} root # vgchange -a n root # cryptsetup luksClose dmcrypt_root
After reboot you will get the following:
>>> better-initramfs started. Kernel version 2.6.35-gentoo-r10 >>> Create all the symlinks to /bin/busybox. >>> Initiating /dev/dir >>> Getting LVM volumes up (if any) Reding all physical volumes. This make take awhile... No volume group found No volume group found >>> Opening encrypted partition and mapping to /dev/mapper/dmcrypt_root Enter passphrase fore /dev/sda2:
Type your password
>>> Again, getting LVM volumes up (if any, after map dmcrypt). Reading all physical volumes. This may take a while... Found volume group "vg" using metadata type lvm2 4 logical volume(s) in volume group "vg" now active >>> Mounting rootfs to /newroot >>> Umounting /sys and /proc. >>> Switching root to /newroot and executing /sbin/init. INIT: version 2.88 booting Loading /libexec/rc/console/keymap OpenRC 0.6.1 is starting up Funtoo Linux (x86_64) ...boot messages omitted for clarity orion login: oleg Password: Last login: Thu Oct 14 20:49:21 EEST 2010 on tty1 oleg@orion ~ %
management
Change your LUKs-encrypted drive's passphrase
You may want to change your encrypted volume’s passphrase or password from time to time. To do so, run the following commands in the console as root:
root # cryptsetup luksChangeKey /dev/sda3
You'll be prompted to enter in the existing passphrase first, then to enter in your new passphrase. You will not be asked to confirm your new passphrase, so be careful when running this operation.