new post, install guide, archlinux with SELinux, full disk encryption and secure boot

2026-01-25 20:10:10 +01:00
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+---
+layout: post
+author: Sam Hadow
+tags: archlinux selinux sysadmin
+---
+
+This post is a guide to install archlinux in UEFI with full disk encryption (LVM on LUKS), SELinux enabled and optionally secure boot.  
+**Warning:** apparmor is much easier to use on archlinux, SELinux on archlinux **will** require you to write some policies manually. Fedora is a better solution if you want SELinux working out of the box and don't want to fight SELinux writing policies. This guide is mostly for advanced users.
+
+## preparing installation media
+
+Follow the initial steps from archlinux [wiki](https://wiki.archlinux.org/title/Installation_guide) to prepare your installation media, the most convenient solution is to copy the ISO to a [ventoy](https://www.ventoy.net/en/index.html) USB key.  
+Then boot your archlinux ISO and first check you have internet access on your computer:
+
+```bash
+ping archlinux.org
+```
+
+If using WiFi, you'll need to use [iwctl](https://wiki.archlinux.org/title/Iwd#iwctl)  
+
+# installation steps
+
+## 1) setting up LVM and preparing volumes
+
+### 1.1) loading the required kernel modules
+
+```bash
+modprobe efivarfs
+modprobe dm-crypt 
+modprobe dm-mod 
+```
+
+### 1.2) partition table
+
+Find the disk you want to use to install your system with `lsblk`. For me it's `vda` as I'm using a virtual machine to write this guide.  
+**important:** Select a GPT parition table type and not MBR.  
+Create a partition table with `cfdisk /dev/vda` (or your prefered tool) and create 2 partitions:
+ `/dev/vda1` as ef EFI (FAT-12/16/32) type, a size of 512MB is fine
+ `/dev/vda2` as 83 Linux filesystem type for the rest of the disk
+
+Write the partition table to the disk.
+
+### 1.3) setting up the encrypted volume
+
+Create the encrypted volume, it will ask you for a confirmation and let you choose a passphrase. (Note that PBKDF2 key derivation algorithm is weaker than Argon2 but is required when using the default grub bootloader, the installation using systemd-boot will not be covered in this guide.)
+
+```bash
+cryptsetup luksFormat --type luks2 --pbkdf pbkdf2 /dev/vda2
+```
+
+Then open it with the passphrase chosen.
+
+```bash
+cryptsetup luksOpen /dev/vda2 luks
+```
+
+### 1.4) setting up LVM
+
+We will create 3 volumes, one for the SWAP, one for the ROOT filesystem and one for the HOME filesystem. Adapt the sizes to what is appropriate for you, in my case I'm using a virtual machine with a 25GB disk so I won't create a huge root volume.
+
+```bash
+pvcreate /dev/mapper/luks
+vgcreate system /dev/mapper/luks
+lvcreate -L 1G -n swap system
+lvcreate -L 10G -n root system
+lvcreate -l 100%FREE -n home system
+```
+
+### 1.5) formating and mounting the volumes
+
+I'll use a BTRFS filesystem but use the filesystem you prefer.
+
+```bash
+#formatting
+mkfs.fat -F32 /dev/vda1
+fatlabel /dev/vda1 BOOT
+mkswap -L SWAP /dev/mapper/system-swap
+mkfs.btrfs -L ROOT /dev/mapper/system-root
+mkfs.btrfs -L HOME /dev/mapper/system-home
+
+#mounting
+swapon /dev/mapper/system-swap
+mount -o compress=zstd /dev/mapper/system-root /mnt 
+mkdir -p /mnt/{home,boot,boot/efi,etc}
+mount -o compress=zstd /dev/mapper/system-home /mnt/home
+mount /dev/vda1 /mnt/boot/efi
+```
+
+Then create the fstab.
+
+```bash
+genfstab -pU /mnt >> /mnt/etc/fstab
+```
+
+## 2) base installation
+
+### 2.1) installing required packages
+
+We'll use reflector to generate the mirrorlist. Adapt the country code to pick the closest mirrors.
+
+```bash
+reflector -c FR -p https -a 12 --sort rate --save /etc/pacman.d/mirrorlist
+```
+
+Then install the required packages and some useful packages.
+
+```bash
+pacstrap -i /mnt base base-devel linux linux-firmware linux-headers pacman-contrib man-pages btrfs-progs vim git bash-completion
+```
+
+### 2.2) chroot
+
+Chroot into the system to continue the installation.
+
+```bash
+arch-chroot /mnt /bin/bash
+```
+
+#### 2.2.1) locales, hostname, clock and timezone
+
+In the file `/etc/locale.gen`, uncomment your locales (for example `en_US.UTF-8 UTF-8`)  
+You can also set your preferences for the virtual console in `/etc/vconsole.conf`, for example for a QWERTY layout:  
+
+```ini
+KEYMAP=us
+FONT=lat9w-16
+```
+
+And in `/etc/locale.conf` (LC_COLLATE=C for case sensitive sorting):
+
+```ini
+LANG=en_US.UTF-8
+LC_COLLATE=C 
+```
+
+And finally generate the locales:
+
+```bash
+locale-gen 
+```
+
+You can set your hostname in `/etc/hostname`.  
+
+For your clock and timezone: (adapt to your timezone)
+
+```bash
+ln -sf /usr/share/zoneinfo/Europe/Paris /etc/localtime
+hwclock --systohc --utc
+```
+
+#### 2.2.2) root password and user creation
+
+Set your root password with `passwd`  
+Then create a user (named sam here) in the wheel group (to use sudo) and set its password with:
+
+```bash
+useradd -m -G wheel sam
+passwd sam
+```
+
+and uncomment the line containing `%wheel ALL=(ALL:ALL) ALL` in `/etc/sudoers`
+
+#### 2.2.3) SELinux installation (from AUR)
+
+Log in as your created user and install an AUR helper to make things easier:
+
+```bash
+su sam
+cd
+git clone https://aur.archlinux.org/yay.git
+cd yay
+makepkg -si
+cd
+```
+
+Then install the required packages for SELinux to work. It will ask you for replacements with conflicting packages, answer yes every time.
+
+```bash
+yay -S libsepol libselinux checkpolicy secilc setools libsemanage semodule-utils policycoreutils selinux-python python-ipy mcstrans restorecond
+yay -S pam-selinux pambase-selinux coreutils-selinux findutils-selinux iproute2-selinux logrotate-selinux openssh-selinux psmisc-selinux shadow-selinux cronie-selinux
+yay -S sudo-selinux
+```
+
+Note: If `sudo-selinux` fails to build, build it with `--nocheck` option:
+
+```bash
+cd ~/.cache/yay/sudo-selinux
+makepkg -si --nocheck
+```
+
+Then exit your user, remodify `/etc/sudoers` to uncomment the line containing `%wheel ALL=(ALL:ALL) ALL` and relog as your user. After that:
+
+```bash
+sudo pacman -S less
+yay -S systemd-selinux systemd-libs-selinux util-linux-selinux util-linux-libs-selinux
+cd ~/.cache/yay/systemd-selinux
+makepkg -si --nocheck
+```
+
+Due to a [cyclic dependency which won't be fixed](https://bugs.archlinux.org/task/39767) the complete build will fail at first, that's why you need to manually build systemd-selinux again after. For some reason less is also required for the build but not a build dependency.  
+Then more SELinux packages and a policy:
+
+```bash
+yay -S selinux-alpm-hook dbus-selinux selinux-refpolicy-arch
+```
+
+If the check fails for `dbus-selinux` build it with `--nocheck` option:
+
+```bash
+cd ~/.cache/yay/dbus-selinux
+makepkg -si --nocheck
+```
+
+If you want to apply a fedora-style user context (as root):
+
+```bash
+semanage login -m -s unconfined_u __default__
+```
+
+#### 2.2.4) necessary packages
+
+Network for next boot:
+
+```bash
+pacman -S networkmanager
+systemctl enable NetworkManager
+```
+
+grub and lvm2:
+
+```bash
+pacman -S grub efibootmgr lvm2
+```
+
+Secure boot:  
+*Note: If you don't want to bother with secure boot, do not run sbctl related command, and later when generating the boot image with grub, remove* `--modules="tpm" --disable-shim-lock` *from the command*
+
+```bash
+pacman -S sbctl
+sbctl create-keys
+sbctl enroll-keys -m
+```
+
+If you also want to enroll hardware security keys, use [systemd-cryptenroll](https://wiki.archlinux.org/title/Systemd-cryptenroll)
+
+#### 2.2.5) opional packages
+
+If you have an intel CPU:
+
+```bash
+pacman -S intel-ucode
+```
+
+If you have a laptop and want battery optimization:
+
+```bash
+pacman -S tlp
+systemctl enable tlp
+```
+
+If you need bluetooth:
+
+```bash
+pacman -S bluez
+systemctl enable bluetooth
+```
+
+If you want 32bits apps (necessary for some packages), in `/etc/pacman.conf` uncomment these lines:
+
+```ini
+#[multilib]
+#include = /etc/pacman.d/mirrorlist
+```
+
+#### 2.2.5) generating boot images
+
+in `/etc/mkinitcpio.conf` on the `MODULES=()` line, add `dm-mod` and in the `HOOKS=()` line you should have:
+
+```ini
+HOOKS=(base udev autodetect modconf block keyboard encrypt lvm2 filesystems fsck)
+```
+
+Then:
+
+```bash
+mkinitcpio -p linux
+```
+
+sbctl post-hook should automatically sign `/boot/vmlinuz-linux`. Otherwise run:
+
+```bash
+sbctl sign -s /boot/vmlinuz-linux
+```
+
+Then in `/etc/default/grub`  
+ uncomment the line `GRUB_UNABLE_CRYPTODISK=y`
+ in `GRUB_CMDLINE_LINUX=""` add `cryptdevice=/dev/vda2:system root=/dev/mapper/system-root`
+ in `GRUB_CMDLINE_LINUX_DEFAULT=""` add `lsm=selinux,landlock,lockdown,yama,integrity,bpf`
+
+Then:  
+
+```bash
+grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=arch_grub --modules="tpm" --disable-shim-lock --recheck
+grub-mkconfig -o /boot/grub/grub.cfg
+sbctl sign -s /boot/efi/EFI/arch_grub/grubx64.efi
+```
+
+*Please note that in a virtual machine you'll need an emulated TPM for the virtual machine to boot if you want secure boot enabled.* 
+
+### 3) exit and reboot
+
+```bash
+exit    # until you exit the chroot
+umount -R /mnt
+swapoff -a
+reboot
+```
+
+### 4) post reboot steps
+
+#### 4.1) relabel files
+
+check SELinux status with `sestatus`, it should be in permissive with refpolicy-arch as the loaded policy.  
+Relabel all the files correctly with the following command:  
+
+```bash
+restorecon -RFv
+```
+
+you might want to clean yay cache before doing that to have less files to relabel:  
+
+```bash
+rm -rf ~/.cache/yay/*
+```
+
+#### 4.2) enable auditd
+
+enable auditd service to read AVC denials from SELinux later.  
+
+```bash
+systemctl enable --now auditd
+```
+
+#### 4.3) create and load necessary policy
+
+Create a file `requiredmod.te` with the following content:
+
+```text
+module requiredmod 1.0;
+
+require {
+        type auditd_etc_t;
+        type getty_t;
+        type var_run_t;
+        type tmpfs_t;
+        type local_login_t;
+        type systemd_tmpfiles_t;
+        type init_runtime_t;
+        type devpts_t;
+        type kernel_t;
+        type device_t;
+        type udev_t;
+        type hugetlbfs_t;
+        type udev_tbl_t;
+        type policy_config_t;
+        type tmp_t;
+        type unconfined_t;
+        type var_lib_t;
+        type systemd_userdbd_runtime_t;
+        type systemd_user_runtime_dir_t;
+        type systemd_sessions_t;
+        type systemd_userdbd_t;
+        type etc_runtime_t;
+        type systemd_logind_t;
+        type file_context_t;
+        type semanage_t;
+        type selinux_config_t;
+        type initrc_runtime_t;
+        type sshd_t;
+        class dir { write add_name remove_name getattr open read search };
+        class file { getattr open read write create getattr ioctl lock relabelfrom relabelto setattr unlink };
+        class sock_file write;
+        class unix_stream_socket { read write ioctl connectto};
+        class capability2 block_suspend;
+        class filesystem { associate quotaget quotamod };
+        class key { link search };
+        class process { noatsecure rlimitinh siginh transition };
+
+}
+
+#============= getty_t ==============
+allow getty_t tmpfs_t:dir { getattr open read };
+allow getty_t var_run_t:file { getattr open read };
+allow getty_t initrc_runtime_t:dir { getattr open read };
+
+#============= local_login_t ==============
+allow local_login_t init_runtime_t:sock_file write;
+allow local_login_t systemd_logind_t:unix_stream_socket connectto;
+allow local_login_t var_lib_t:dir { add_name remove_name };
+allow local_login_t var_lib_t:file { create getattr lock open read setattr unlink write };
+
+#============= sshd_t ==============
+allow sshd_t local_login_t:key { link search };
+allow sshd_t systemd_logind_t:unix_stream_socket connectto;
+allow sshd_t unconfined_t:process { noatsecure rlimitinh siginh };
+
+#============= systemd_tmpfiles_t ==============
+allow systemd_tmpfiles_t auditd_etc_t:dir search;
+allow systemd_tmpfiles_t auditd_etc_t:file getattr;
+
+#============= systemd_sessions_t ==============
+allow systemd_sessions_t kernel_t:dir search;
+allow systemd_sessions_t kernel_t:file { getattr ioctl open read };
+
+#============= systemd_user_runtime_dir_t ==============
+allow systemd_user_runtime_dir_t etc_runtime_t:file { open read };
+allow systemd_user_runtime_dir_t kernel_t:dir search;
+allow systemd_user_runtime_dir_t kernel_t:file { getattr ioctl open read };
+allow systemd_user_runtime_dir_t systemd_userdbd_runtime_t:sock_file write;
+allow systemd_user_runtime_dir_t systemd_userdbd_t:unix_stream_socket connectto;
+allow systemd_user_runtime_dir_t tmp_t:dir read;
+allow systemd_user_runtime_dir_t tmpfs_t:filesystem { quotaget quotamod };
+
+#============= systemd_userdbd_t ==============
+allow systemd_userdbd_t initrc_runtime_t:dir { getattr open read search };
+
+#============= devpts_t ==============
+allow devpts_t device_t:filesystem associate;
+
+#============= hugetlbfs_t ==============
+allow hugetlbfs_t device_t:filesystem associate;
+
+#============= kernel_t ==============
+allow kernel_t self:capability2 block_suspend;
+
+#============= tmpfs_t ==============
+allow tmpfs_t device_t:filesystem associate;
+
+#============= udev_t ==============
+allow udev_t kernel_t:unix_stream_socket { read write ioctl };
+allow udev_t udev_tbl_t:dir { write add_name };
+allow udev_t var_run_t:sock_file write;
+```
+
+Run the following command to compile and load the module:
+```bash
+checkmodule -m -o requiredmod.mod requiredmod.te
+semodule_package -o requiredmod.pp -m requiredmod.mod
+semodule -i requiredmod.pp
+```
+
+And set a few booleans:
+
+```bash
+setsebool -P allow_polyinstantiation on
+setsebool -P systemd_tmpfiles_manage_all on
+setsebool -P ssh_sysadm_login on
+```
+
+Then in `/etc/selinux/config`, set SELinux mode to enforcing instead of permissive and reboot.  
+And that's it, you now have a minimal archlinux installation in UEFI with full disk encryption, secure boot, and SELinux in enforcing mode.