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663 lines
33 KiB
Text
663 lines
33 KiB
Text
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Installing Slackware on encrypted volumes
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=========================================
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Contents:
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* Introduction
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* Using cryptsetup during Slackware installation
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* Encrypting your '/home' partition
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* Encrypted swap
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* Encrypted root filesystem
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* Combining LUKS and LVM
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* Hibernation (suspend-to-disk)
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* Additional passphrases, keyfiles
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* A note on custom kernels
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* USB keyboards and LUKS
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* A mkinitrd helper script
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Introduction
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------------
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Increasingly common in modern Linux distributions is the ability to
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install onto an encrypted partition (or drive, or volume). Especially for
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people with a laptop who are traveling a lot, it adds a lot to the security
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of your data if access to that data is denied to the potential thief of
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your computer.
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Starting with release 12.0, Slackware has support for LVM built into the
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installer. With a little more effort, the installer offers the opportunity to
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use transparent encryption on the partitions/volumes/disks where you install
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Slackware. You can combine the use of LVM and encryption to minimize the
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number of times you need to enter an unlock passphrase. If you want to know
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more about setting up and using LVM during the installation, read the file
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'README_LVM.TXT'.
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Slackware uses device-mapper and cryptsetup to achieve transparent
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encryption of your data partitions and your swap. Cryptsetup uses a
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concept called LUKS (Linux Unified Key Setup) which enables you to change
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your unlock password for the encrypted volume without having to re-encrypt
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all of your data. You can even assign multiple passphrases to an encrypted
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volume, so that other people besides you are able to unlock the encryption
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without the need to know _your_ passphrase.
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When preparing a partition for transparent encryption with cryptsetup,
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the program will ask you for a password. This password is used to encrypt
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another randomly generated password and this particular password is used
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to actually encrypt the data inside the mapped volume. Cryptsetup will
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create a mapped device and make this block device available under the
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'/dev/mapper' directory. Any data read from or written to this mapped device
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will automatically be decrypted from / encrypted to the actual partition.
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A big NOTE finally. When you encrypt your root filesystem, you will have
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to make sure that there will be at least one (small) partition which is
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left unencrypted. This partition must contain the kernel(s) you want to boot
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from, and the initrd image that is needed with encrypted volumes. You need
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to install LILO either to the MBR - or if that is not possible, into the
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root sector of this small unencrypted partition. You will probably guess
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why we cannot use an encrypted partition for this...
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Using cryptsetup during Slackware installation
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----------------------------------------------
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We are going to enable encryption on some or all of our partitions or
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volumes before installing Slackware onto them. The first section to follow
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deals with encrypting a single partition which is not the root partition.
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Typically, people have a need to encrypt their home directories and that is
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where that section will focus on. Next is a section on encrypting your
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swap partition in addition to your /home partition. The swap partition
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contains valuable information for a data thief, even after you power off
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your computer. By encrypting the swap partition we deny the potential thief
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access to this data. The section following that will show you how to get
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a fully encrypted system, by encrypting the root ('/') filesystem as well.
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This is a little harder to do, but probably worth the effort.
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To make it more interesting, _and_ easier to use, we will devote a final
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section to using a combination of LVM and disk encryption. As an example,
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we will create a single big encrypted partition, and inside that encrypted
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'container' we create several Logical Volumes which we will use as our root
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(/), /home and swap partitions. The advantages of this approach are, that you
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will need only a single passphrase to unlock your computer, and you will not
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have to maintain an '/etc/crypttab' file containing information about encrypted
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volumes that need to be unlocked during boot-up. Additionally, we will be
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rewarded with a swap partition that we can use for suspend-to-disk and that
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will remain encrypted after shutdown (so that for instance a potential data
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thief will not be able to get to your valuable data even if you hibernated
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your laptop).
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If you choose this last option to get a fully encrypted Slackware, it is
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advisable to read the 'README_LVM.TXT' file to make yourself more familiar
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with the process of creating and using Logical Volumes during installation
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of Slackware. And then, skip right through to the section of this document
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called "Combining LUKS and LVM".
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Encrypting your '/home' partition
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---------------------------------
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After the computer boots up from the install CD/DVD (or USB flash disk,
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or PXE) and you find yourself at the '#' prompt, the first thing to do is
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use 'fdisk' or 'cfdisk' to create any partitions you need for your Slackware.
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Next, use 'cryptsetup' to prepare the partitions you intend to be
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encrypted. Note: this section of the README concerns itself with setting
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up encrypted *data* partitions. If you want to know how to configure an
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encrypted *swap* partition, skip to the section called "Encrypted swap".
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Suppose, you want to encrypt the partition called '/dev/sdx2' and use it
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as your '/home' filesystem. (Please replace '/dev/sdx2' with the name of YOUR
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PARTITION in the next series of examples). Several of the commands shown below
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will irrevocably destroy any data that you currently have on the partition. It
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is a good idea to double check the output from 'fdisk -l' before you start.
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* To begin with, we are going to fill the partition with random data. This
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will make it a lot harder for any forensics expert to determine where your
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encrypted data resides on that partition after we're finished installing
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Slackware onto it. The process will take a long time - depending on the
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size of your partition it may take hours or more. if you're not _too_
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concerned with the possibility of an FBI agent confiscating your computer,
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you can skip this command:
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# dd if=/dev/urandom of=/dev/sdx2
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* Prepare the partition for encryption. You will be asked twice to enter
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a passphrase. Note that a passphrase is not limited to a single word. The
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passphrase may contain spaces.
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# cryptsetup -y luksFormat /dev/sdx2
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You can dump information about the encrypted partition to your console by
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running the following command:
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# cryptsetup luksDump /dev/sdx2
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* Now we will 'open' the encrypted partition and let the devicemapper create
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a mapped block device. We will use the mapped device which behaves just like
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an ordinary disk partition when we get to the TARGET selection in 'setup'. The
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mapped device nodes will be created in the directory '/dev/mapper'. The command
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will ask you for the passphrase which you entered during the "luksFormat"
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operation. The last argument that the command takes is the name of the mapped
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device. We will call our mapped device 'lukssdx2' (note that LUKS expects the
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mapped device name to be in the format of "luks<rawdevname>"). It will be
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available for use as the block device '/dev/mapper/lukssdx2', e.g. if the raw
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device name is "/dev/sda2", then the mapped name will be "/dev/mapper/lukssda2".
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# cryptsetup luksOpen /dev/sdx2 lukssdx2
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* We've now finished our preparations, and it is time to start the 'setup'
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program and install Slackware. This setup does not differ at all from the
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setup you have become used to. The only notable difference lies in the
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names of the devices you will select for your target partitions. Be sure
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to read until the end of the story though, because we will have to do some
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postprocessing in order to make your encrypted partitions available after
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reboot (setup cannot yet do all of this automatically).
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* In setup, under "ADDSWAP", proceed as usual and configure a normal
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unencrypted swap partition, even if you want to have your swap encrypted.
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We will take care of swap encryption after the installation of Slackware
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finishes.
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* In setup, when you choose "TARGET" in the main menu, you will notice that
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the mapped device is available in the 'Linux partition' selection as
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"/dev/mapper/lukssdx2". Select the partition you designated for your
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root ('/') filesystem, and next select "/dev/mapper/lukssdx2" for your
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'/home' filesystem. Create any filesystem you like on them. My favorite
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fstype is ext4, but you can choose xfs or jfs for stability and speed.
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NOTE: The underlying partition will *also* be visible in the target selection
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menu. Be very careful NOT to select this device ('/dev/sdx2' in our
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example) for any other filesystem you wish to create, or you will
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destroy the data on the encrypted partition.
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* Let the installation complete, and after you select "EXIT" make sure to
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choose not to reboot and you will be returned to the command prompt. DO
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NOT reboot just yet! We are going to create a configuration file for
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the cryptsetup program, called '/etc/crypttab'. This file contains the
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information cryptsetup needs for unlocking your encrypted volume and mapping
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it to the correct device name. The file '/etc/crypttab' contains lines of the
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format: "mappedname devicename password options". Since we are still inside
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the installer, the root filesystem of our fresh Slackware installation is
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still mounted under '/mnt'. For our example where we encrypted '/dev/sdx2'
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and mapped the unlocked device to '/dev/mapper/lukssdx2', we need this
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single line in '/etc/crypttab':
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lukssdx2 /dev/sdx2
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So, we need to run the command:
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# echo "lukssdx2 /dev/sdx2" > /mnt/etc/crypttab
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in order to create the file with the required content (I am assuming here
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that the file did not yet exist... the above command will overwrite the
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data in the file should it have existed). You can of course also just
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start the 'vi' editor and add the above line. When the password is not
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listed in the crypttab file (potentially very unsafe of course) cryptsetup
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will ask you for the password when your computer boots.
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Encrypted swap
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--------------
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In the previous chapter we have installed Slackware using an encrypted
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/home partition, but left the swap partition unencrypted. We are going
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to take care of that 'omission' right now, because we do not want to give
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a potential data thief access to any sensitive data which landed on your
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disk because of the kernel's memory swapping process.
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It really is very simple and straight-forward. It is also independent of
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whether or not you are using encryption for any other (data) partition.
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Add the following line to the 'crypttab' file on your fresh installation
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of Slackware - for the sake of this example I am assuming that the swap
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partition you chose is '/dev/sdx3':
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cryptswap /dev/sdx3 none swap
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You can use the 'vi' editor to add this line to '/mnt/etc/crypttab'.
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You can also choose to run the following command which adds that line to
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the end of the file:
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# echo "cryptswap /dev/sdx3 none swap" >> /mnt/etc/crypttab
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We need to edit the 'fstab' file of your Slackware installation so that
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the correct device will be used for the swap after your computer reboots
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(the device '/dev/sdx3' will no longer be useful, but '/dev/mapper/cryptswap
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will'). The line in '/mnt/etc/fstab' for your swap will look like this at
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first:
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/dev/sdx3 swap swap defaults 0 0
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and you will have to change it so that it becomes like this:
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/dev/mapper/cryptswap swap swap defaults 0 0
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These two edits are sufficient. The above instructions assume that you
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edited the 'crypttab' file at the end of a Slackware installation, but in
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fact you can do this at any time. The Slackware boot-up process will
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take care of the rest. At shutdown of your Slackware, the encrypted swap
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partition will be reformatted as a normal unencrypted swap, so that any
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other OS-es you might be running in a multi-boot configuration will have
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no problems in using this swap partition as well.
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NOTE: the swap partition is encrypted with a new randomly generated key every
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time your computer boots.
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There is no need to ever enter a passphrase!
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NOTE: having an encrypted swap like this causes a re-format of the swap
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partition on every boot-up and shutdown. This is perfectly OK as long
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as you do not change the order of your hard disks. If you add a disk,
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or move this disk to another computer, the device name may change (for
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instance from sda to sdb) and if you forget to modify '/etc/crypttab'
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your system may end up formatting the wrong partition!
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For this reason alone, it is recommended that you implement disk
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encryption including swap using the "Combining LUKS and LVM" method
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described in the chapter with the same name!
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Encrypted root filesystem
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-------------------------
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You can go one step further than merely encrypting your '/home'
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filesystem's partition. You can choose to encrypt _all_ of your Slackware
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partitions, including the root partition. In that case you will have to
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perform some additional post-install configuration before you reboot your
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Slackware box.
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NOTE: the method described here will result in having several independently
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encrypted partitions. This may require you to enter multiple
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passphrases in order to unlock all of these partitions. If you want to
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unlock your complete system using a single passphrase, and if you do
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not shy back from using LVM, then the better alternative is to follow
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the instructions in the "Combining LUKS and LVM" chapter which follows
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next. If you think that LVM adds one layer of complexity too much,
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then just read on and implement the solution described right here.
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* Be sure to create a small partition which you leave *unencrypted*. Tell
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the installer to mount it under '/boot'. The kernel and the initrd (with
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the cryptsetup and additional required kernel modules) will go there. We are
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going to assume that Slackware is the only OS on the computer so that you
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can tell lilo to install the bootloader in the MBR (which is the default
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option). Lilo is able to boot a Windows if you already had that installed on
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your computer, so even in the dual-boot situation it should be safe to use
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the MBR. With other Linux distributions already present on the computer,
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things may be a little more difficult - you will have to install lilo to
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the /boot partition then.
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* Perform a Slackware install just like I described above, creating
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additional encrypted partitions and mapping them to appropriate names -
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for this example I assume that you map the encrypted root partition
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'/dev/sdx2' to 'lukssdx2'. When the LILO configuration pops up, tell lilo
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that your root partition is '/dev/mapper/lukssdx2'. Lilo will try to
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install and fail, and will tell you so. It will however have written a
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'lilo.conf' file which we can edit in a follow-up action. Proceed with
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the installation and at the end, exit the setup program but do _not_
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reboot just yet.
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* After you are returned to the command prompt, perform a 'chroot' into the
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new installation. All the filesystems are still mounted, and the Slackware
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installer will already have mounted the /sys and /proc filesystems for use
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in the 'chroot'. We only need to run the following command:
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# chroot /mnt
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* Next, now that we are in the chroot, create the initrd with LVM (if you
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used Logical Volumes) and CRYPT support - or else your Slackware computer
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will not be able to proceed past the initial stage of booting the kernel.
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The initial ramdisk (initrd) contains a small filesystem with the tools
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needed to unlock the root filesystem, so that the kernel can start the init
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program. In the example command line below which creates the 'initrd.gz'
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image I assume that the root filesystem is 'ext4', we used the mapped device
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'cryptroot' for the root filesystem on the real partition '/dev/sdx1',
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and are running the Slackware 14.2 default SMP kernel '4.4.14-smp'
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and we did not use Logical Volumes (more about that in the next section):
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# mkinitrd -c -k 4.4.14-smp -m ext4 -f ext4 -r lukssdx2 -C /dev/sdx2
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* The resulting initrd image will be written to the file '/boot/initrd.gz'
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by default. We still need to tell lilo about this initrd. Open the
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configuration file '/etc/lilo.conf' in an editor such as vi or pico -
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it should already have been generated by the 'liloconfig' part of setup.
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Look for the "Linux bootable partition config" and add a line for the initrd.
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We also need to change the kernel file to a generic kernel, because lilo
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is unable to combine the 'huge' kernels in Slackware 14.0 with an initrd
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image - it will complain about "The initial RAM disk is too big to fit
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between the kernel and the 15M-16M memory hole" if you try with a 'huge'
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kernel. We can live with that, since the 'huge' kernels are not meant
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for day-to-day use anyway. They are meant to install Slackware on a wide
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range of computers and that is why they are 'huge'. The linux part of
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'/etc/lilo.conf' should end up looking somewhat like this:
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image = /boot/vmlinuz-generic-smp-4.4.14-smp
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initrd = /boot/initrd.gz
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root = /dev/mapper/lukssdx2
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label = linux
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read-only
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If you add the above section as an extra instead of editing what's already
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present, make sure that the label you use ('linux' in the example above)
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is unique in the configuration file.
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* If you have another OS on your computer and cannot install lilo to the
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MBR, you will have selected "Install to superblock (Root)" instead. In
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that case, we have one additional change to make, and that is almost at the
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top of the file. Look up the line that says "boot = /dev/mapper/lukssdx2"
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which is the device for your root partition and which was the reason for
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lilo failing to install. Change the boot device to the name of the small
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*unencrypted* partition you've created at the beginning and which is
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mounted under '/boot'. Assuming the name of that partition is '/dev/sdx1',
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the "boot =" line must become like this:
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boot = /dev/sdx1
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We are done. Write the changes, exit the editor and run the command 'lilo'.
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Lilo will issue a couple of warnings concerning a difference in what
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'/proc/partitions' reports and what lilo thinks are the available partitions,
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but it is safe to ignore these.
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Reboot now, and you will be presented with a "Enter passphrase: "
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prompt. After entering the passphrase which unlocks your root filesystem,
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the system will boot into Slackware. If there are other encrypted partitions,
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you will be prompted for their respective passphrases, too.
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Combining LUKS and LVM
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----------------------
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Until now, we have been occupying ourselves with encrypting separate
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partitions. This is all fully functional, but there are a few drawbacks.
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One, you will need to enter a passphrase for every partition you have encrypted
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(except for the swap which Slackware encrypts with a random passphrase
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on every boot). Two, the method used for encrypting the swap partition
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prohibits the use of the swap as a hibernation partition. And since the
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initrd of Slackware 14.0 supports hibernation, it would be a shame not to be
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able to use this feature on your laptop (which, because of it's portability,
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is the primary target for full disk encryption anyway).
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This section of the README_CRYPT.TXT will deal with these drawbacks and
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offer you full disk encryption (including swap) that needs only a single
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passphrase to unlock and allows for hibernation (suspend-to-disk).
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We are assuming that Slackware will be the only Operating System on your
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computer. In case you already have an OS installed (such as MS Windows), the
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procedure may be a little different because you cannot always install lilo to
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the MBR. After booting from the Slackware installation medium, we will
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create a small unencrypted partition that will contain the Linux kernels and
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the initrd image(s). The rest of the disk's free space will be dedicated to
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a single partition which we are going to encrypt. On top of the encrypted
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volume, we are going to create several Logical Volumes, and these LV's
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are going to be formatted as our Slackware partitions ('/', '/home' and
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'swap'). These are the steps in more detail:
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* Use (c)fdisk to create your partitions. For the sake of this example, I
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am going to assume that /dev/sdx1 is a 100 MB large partition and /dev/sdx2
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is the large partition that eats up the remainder of your disk's free space.
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* First, create a LUKS-encrypted volume on top of /dev/sdx2 after you
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have optionally filled the partition with random data (read the section
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"Encrypting your '/home' partition" for more information about why you
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would want to fill your partition with random data first):
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# dd if=/dev/urandom of=/dev/sdx2
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* Prepare the partition for encryption. You will be asked twice to enter
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a passphrase. Note that a passphrase is not limited to a single word. The
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passphrase may contain spaces.
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# cryptsetup -y luksFormat /dev/sdx2
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* Open the encrypted partition so that we can start using the mapped device
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which exposes the partition as an unencrypted block device. The command
|
|
will ask you for the passphrase which you entered during the "luksFormat"
|
|
operation. The last argument that the command takes is the name of the mapped
|
|
device. We will call our mapped device 'lukssdx2' because the installed
|
|
system will use that name (predictability is a good thing).
|
|
|
|
# cryptsetup luksOpen /dev/sdx2 lukssdx2
|
|
|
|
* The LVM part is next. Create a Physical Volume (PV) on device
|
|
'/dev/mapper/lukssdx2', a Volume Group (VG) called 'cryptvg' - any name will
|
|
do - on the PV, and three Logical Volumes (LV's) in the VG, one for your
|
|
root partition (7 GB in size), one for the /home partition (10 GB in size)
|
|
and a third which we will use for swap (1 GB in size). You will probably
|
|
use different sizes depending on your environment and wishes, but keep the
|
|
sum of the LV sizes less than the total size of the Physical Volume:
|
|
|
|
# pvcreate /dev/mapper/lukssdx2
|
|
|
|
# vgcreate cryptvg /dev/mapper/lukssdx2
|
|
|
|
# lvcreate -L 7G -n root cryptvg
|
|
|
|
# lvcreate -L 10G -n home cryptvg
|
|
|
|
# lvcreate -L 1G -n swap cryptvg
|
|
|
|
* Run 'mkswap' so that the 'setup' program will identify the 'swap'
|
|
LV as a valid swap partition:
|
|
|
|
# mkswap /dev/cryptvg/swap
|
|
|
|
* With the system properly prepared, you can launch 'setup'. The 'setup'
|
|
program will identify the LV swap volume and activate it. When appointing
|
|
the partitions to use for your filesystems, select '/dev/cryptvg/root' for the
|
|
root partition, next select '/dev/cryptvg/home' to be used for your /home .
|
|
And lastly, assign the partition /dev/sdx1 to a /boot filesystem. This
|
|
'/boot' filesystem will be the only unencrypted part of your computer.
|
|
|
|
You will notice that there are several more devices to select from but
|
|
*don't* touch these! The devices such as /dev/mapper/* are the underlying
|
|
device names for the encrypted and LVM volumes. If you choose to touch any
|
|
of these, you will destroy the data on the /dev/cryptvg/* volumes which you
|
|
are using.
|
|
After partitioning, we end up with a filesystem configuration like this:
|
|
|
|
/dev/cryptvg/root /
|
|
/dev/cryptvg/home /home
|
|
/dev/sdx1 /boot
|
|
|
|
* When installation of the packages has finished, the system configuration will
|
|
start, and one of the dialogs will be for 'liloconfig'. The assumption is that
|
|
you are installing Slackware as the only OS on your computer. This means that
|
|
you must install lilo to the MBR. Even if you have another OS like MS Windows
|
|
installed already, Slackware's lilo bootloader will be able to boot Windows
|
|
if you install lilo to the MBR. Choose "expert lilo configuration" with the
|
|
option "Install to Master Boot Record (MBR)". Select '/dev/cryptvg/root' as
|
|
the root partition to boot. Add any Windows partition to lilo if you want to
|
|
dual-boot Windows. Finally, when liloconfig installs the bootloader, you may
|
|
see an error message stating that the "installation failed". Ignore this,
|
|
because we will have to add an initrd to '/etc/lilo.conf' anyway and re-run
|
|
lilo. We will do this after the Slackware installation has come to it's end.
|
|
|
|
* Let the installation complete, and after you select "EXIT" you will be
|
|
returned to the command prompt. DO NOT reboot just yet! This is the moment
|
|
where we fix our bootloader. To do so, we will 'chroot' (change root) into
|
|
our freshly installed Slackware filesystem. The setup program has done all
|
|
the preparations already, such as re-mounting /sys and /proc below /mnt and
|
|
generating LVM device nodes in /mnt . Enter the 'chroot' using the command:
|
|
|
|
# chroot /mnt
|
|
|
|
* In the chroot, you create an initrd image with LVM and CRYPT support -
|
|
or else your Slackware computer will not be able to proceed past the initial
|
|
stage of booting the kernel. The initial ramdisk (initrd) contains a small
|
|
filesystem with the tools needed to unlock the root filesystem, so that
|
|
the kernel can start the init program. In the example command line below
|
|
which creates the 'initrd.gz' image I assume that you formatted the root
|
|
filesystem as 'ext4', and will be running the Slackware 14.2 default SMP
|
|
kernel '4.4.14-smp' :
|
|
|
|
# mkinitrd -c -k 4.4.14-smp -m ext4 -f ext4 -r /dev/cryptvg/root -C /dev/sdx2 -L
|
|
|
|
NOTE: if you use a non-US keyboard and need to enter a passphrase during boot,
|
|
this may be problematic if the keyboard mapping is US while Slackware
|
|
runs from the initrd filesystem. In this case, add support for your
|
|
keyboard to the initrd image using this additional parameter to the
|
|
'mkinitrd' command above: "-l <language>". The string <language> is the
|
|
same as the one you select in the installer when your keyboard is
|
|
non-US. Example for a dutch keyboard: "-l nl".
|
|
|
|
* The resulting initrd image will be written to the file '/boot/initrd.gz'
|
|
by default. We still need to tell lilo about this initrd, so open the
|
|
configuration file '/etc/lilo.conf' in an editor such as vi or pico -
|
|
it should already have been generated by the 'liloconfig' part of setup.
|
|
Look for the "Linux bootable partition config" and add a line for the initrd.
|
|
We also need to change the kernel file to a generic kernel, because lilo
|
|
is unable to combine the 'huge' kernels in Slackware 14.2 with an initrd
|
|
image - it will complain about "The initial RAM disk is too big to fit
|
|
between the kernel and the 15M-16M memory hole" if you try a 'huge'
|
|
kernel. We can live with that, since the 'huge' kernels are not meant
|
|
for day-to-day use anyway. They are meant to install Slackware on a wide
|
|
range of computers and that is why they are 'huge'. The linux part of
|
|
'/etc/lilo.conf' should end up looking somewhat like this:
|
|
|
|
image = /boot/vmlinuz-generic-smp-4.4.14-smp
|
|
initrd = /boot/initrd.gz
|
|
root = /dev/cryptvg/root
|
|
label = linux
|
|
read-only
|
|
|
|
If you add the above section as an extra instead of editing what's
|
|
already present, make sure that the label you use ('linux' in the example
|
|
above) is unique in the configuration file.
|
|
|
|
We are done. Save your changes, exit the editor and run the command
|
|
'lilo'. Lilo will issue a couple of warnings concerning a difference in
|
|
what '/proc/partitions' reports and what lilo thinks are the available
|
|
partitions, but it is safe to ignore these. Reboot now, and you will be
|
|
presented with a "Enter passphrase: " prompt. After entering the passphrase
|
|
which unlocks your encrypted partition, the system will boot into Slackware.
|
|
You will be able to work as usual, and when you shut the machine down (or
|
|
suspend to disk using the swap partition) all your data (including swap)
|
|
will be encrypted when stored on disk.
|
|
|
|
As you may have noticed, there was no need to create a file '/etc/crypttab'
|
|
this time. Also, there is only a single passphrase to enter. Additionally,
|
|
the swap is encrypted by default which is a big plus if you intend to use a
|
|
laptop and carry it around with you in a hibernated state. All considered,
|
|
this is the most elegant way of encrypting your Slackware computer if you
|
|
do not mind using LVM.
|
|
|
|
|
|
Additional passphrases, keyfiles
|
|
--------------------------------
|
|
|
|
The cryptsetup program assigns 7 'key slots' to any partition or volume
|
|
it encrypts. Each of those seven slots can contain a key to unlock the
|
|
partition's data. The key can be a passphrase, but the content of a
|
|
*keyfile* is another option. You can then pass the name of a file as a
|
|
parameter to cryptsetup in order to unlock an encrypted volume so that
|
|
you won't have to type a passphrase. This creates the possibility to
|
|
use a keyfile on a removable USB flash disk for unlocking your Slackware
|
|
computer. Slackware supports keyfiles: if the file can be found on the file
|
|
system, it will be used and you won't have to type a passphrase.
|
|
|
|
A keyfile on a FAT formatted USB stick can be used as well. This scenario
|
|
requires you to use the "-K" parameter to mkinitrd to specify the USB stick's
|
|
FAT-label or UUID, as well as the full path to the keyfile. An example:
|
|
|
|
# mkinitrd -c -k 4.4.14-smp -m ext4 -f ext4 -r /dev/cryptvg/root -C /dev/sdx2 -L -K LABEL=TRAVELSTICK:/keys/alien.luks
|
|
|
|
The mkinitrd of Slackware 13.1 introduced this support for USB sticks as
|
|
unlocking mechanism. Alternatively, after the root filesystem is unlocked
|
|
and mounted, it is completely safe to have a keyfile for _additional_
|
|
encrypted filesystems stored in for instance the '/root' directory.
|
|
That way, you still have only one passphrase to type.
|
|
|
|
|
|
Hibernation (suspend-to-disk)
|
|
-----------------------------
|
|
|
|
I will touch briefly on the subject of enabling 'suspend-to-disk'
|
|
because it is not documented properly anywhere else. Configuring your
|
|
Slackware computer for hibernation can be done at any time, it is not
|
|
required to do this during installation of Slackware. Suppose you want
|
|
to use the swap partition '/dev/cryptvg/swap' for hibernation, then you
|
|
must perform the following two steps:
|
|
(1) add "resume=/dev/cryptvg/swap" to the 'append =' line in your
|
|
'/etc/lilo.conf' file. The 'append' line may end up looking like this:
|
|
append = "vt.default_utf8=0 resume=/dev/cryptvg/swap"
|
|
(2) add "-h /dev/cryptvg/swap" as an extra parameter to your mkinitrd command
|
|
to create an initrd with support for resuming from a swap partition.
|
|
Do not forget to run 'lilo' after creating the new initrd.gz file!
|
|
|
|
|
|
A note on custom kernels
|
|
------------------------
|
|
|
|
If you want to compile your own custom kernel to work with LUKS encrypted
|
|
partitions, you need to enable at least the following two options in your
|
|
kernel configuration:
|
|
|
|
Multiple devices driver support (RAID and LVM) --->
|
|
<*> Device mapper support
|
|
<*> Crypt target support
|
|
|
|
This is equivalent to the following options in your .config file:
|
|
|
|
CONFIG_BLK_DEV_DM=y
|
|
CONFIG_DM_CRYPT=y
|
|
|
|
Do not compile these as module! They are required in your kernel.
|
|
|
|
|
|
USB keyboards and LUKS
|
|
----------------------
|
|
|
|
If you have set up an encrypted root partition, you will need to have
|
|
access to your keyboard in order to type the passphrase. This may require
|
|
you to add the 'uhci-hcd' and 'usbhid' modules to your initrd image if you
|
|
have a USB keyboard. Also note that if you are using a non-US keyboard,
|
|
you can use the '-l' parameter to the 'mkinitrd' command in order to add
|
|
support for this keyboard to your initrd.
|
|
|
|
|
|
A mkinitrd helper script
|
|
------------------------
|
|
|
|
The mkinitrd package in Slackware 14.0 (and on) ships with a script called
|
|
'mkinitrd_command_generator.sh'. If you run this script, it will analyze
|
|
your Slackware configuration and make a smart suggestion about the 'mkinitrd'
|
|
command you have to type in order to create an initrd.gz with all the bells
|
|
& whistles. The script will recognize your kernel version, root partition
|
|
and filesystem, it will find out if you are using LUKS and/or LVM and will
|
|
determine what kernel modules your initrd needs to mount the root filesystem.
|
|
The following command will save you the headache of figuring this out all
|
|
by yourself:
|
|
|
|
# /usr/share/mkinitrd/mkinitrd_command_generator.sh -r
|
|
|
|
It should emit a string like this (your system will probably give different
|
|
parameter values):
|
|
|
|
mkinitrd -c -k 4.4.14-smp -m ext4 -f ext4 -r /dev/cryptvg/root -C /dev/sdx2 -L
|
|
|
|
You can copy and paste this output to your command prompt, and add any other
|
|
parameters you need such as "-h" to indicate a hibernation partition or
|
|
"-l" to indicate you are using a non-US keyboard layout. You can even run
|
|
the script in full interactive mode by using the "-i" parameter, and it will
|
|
guide you through the process of generating a mkinitrd commandline.
|
|
|
|
|
|
Desktop Environments
|
|
--------------------
|
|
|
|
You probably will not want your encrypted volume to appear on the desktop
|
|
of e.g. KDE or Xfce as a mountable device, so something like this should
|
|
prevent that from occurring:
|
|
|
|
# cat /etc/udev/rules.d/99-ignore-luksdevs-on-desktop.rules
|
|
KERNEL=="sdx2", ENV{UDISKS_IGNORE}="1"
|
|
|
|
|
|
==============================================================================
|
|
|
|
Good luck with your fresh Slackware installion on encrypted partition(s)!
|
|
|
|
==============================================================================
|
|
Author:
|
|
Eric Hameleers <alien@slackware.com> 18-sep-2012
|
|
Edits by:
|
|
Robby Workman <rworkman@slackware.com> 9 March 2017
|
|
URLs:
|
|
http://www.slackware.com/~alien/dokuwiki/doku.php?id=slackware:setup
|
|
|