01/01: website: Add post about installing XFCE on a foreign distribution.

[Marius Bakke]

mbakke pushed a commit to branch master
in repository guix-artwork.

commit eed6f3fc58ea90f25f5a3e13ac58943813b387e7
Author: Marius Bakke <address@hidden>
Date:   Sun Nov 17 18:48:59 2019 +0100

    website: Add post about installing XFCE on a foreign distribution.
    
    * website/posts/guix-xfce-desktop-on-foreign-distribution.md: New file.
---
 .../guix-xfce-desktop-on-foreign-distribution.md   | 304 +++++++++++++++++++++
 1 file changed, 304 insertions(+)

diff --git a/website/posts/guix-xfce-desktop-on-foreign-distribution.md 
b/website/posts/guix-xfce-desktop-on-foreign-distribution.md
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+title: Running a Guix XFCE Desktop on CentOS 7
+date: 2019-11-17 19:00
+author: Marius Bakke
+tags: XFCE, foreign distribution
+---
+
+This tutorial will show how to run a fully fledged XFCE desktop environment
+installed with Guix on top of an existing GNU/Linux distribution.  This guide
+uses CentOS 7 as the base operating system and assumes that Xorg is already
+configured and running on VT2 under a different user account.
+
+We will borrow Xorg and `xinit` from the host distribution and run Guix XFCE on
+virtual terminal 4 as user 'alice'.  No system-wide configuration files need to
+be touched (apart from the Guix install), but we do make a couple of changes
+for convenience.
+
+#### From scratch to XFCE
+
+If Guix is not already installed, go grab the
+[installation 
script](https://git.savannah.gnu.org/cgit/guix.git/plain/etc/guix-install.sh)
+and run it as `sudo bash guix-install.sh`.
+
+The script creates `/gnu/store/` and `/var/guix/` and configures a system 
service
+for `guix-daemon`.  By default the daemon runs from the 'root' users Guix; we
+won't be using the root account in this guide, so let's start by making the
+guix-daemon service refer to our local user 'alice' instead.
+
+```sh
+sudo sed -i 's/root/alice/' /etc/systemd/system/guix-daemon.service
+```
+
+Now every time Alice runs 'guix pull', the daemon gets updated too.  If you
+installed Guix just now, make sure to run `guix pull` before proceeding 
further.
+
+Next we'll add some lines to Alices `.bash_profile` to set up PATH and related
+variables:
+
+```sh
+GUIX_PROFILE="${HOME}/.guix-profile"
+[[ -L "${GUIX_PROFILE}" ]] && . "${GUIX_PROFILE}/etc/profile"
+
+export PATH="${HOME}/.config/guix/current/bin:${PATH}"
+export INFOPATH="${HOME}/.config/guix/current/share/info:${INFOPATH}"
+export MANPATH="${HOME}/.guix-profile/share/man:/usr/share/man"
+
+export 
XDG_CONFIG_DIRS="${HOME}/.desktop-profile/etc/xdg:${HOME}/.guix-profile/etc/xdg"
+export 
XDG_DATA_DIRS="${HOME}/.desktop-profile/share:${HOME}/.guix-profile/share"
+```
+
+This will look familiar if you have used Guix on a foreign distribution before.
+The `XDG_` variables tell XFCE where to look for installed programs and things
+like autostart files: we want minimal interference from the host system, so we
+"hard code" them to refer to just our Guix profiles.
+
+We will install XFCE and related programs to a
+[separate Guix 
profile](https://guix.gnu.org/cookbook/en/html_node/Guix-Profiles-in-Practice.html)
+that can be updated and rolled back independently of the main user profile.
+That allows us to distinguish between "stable desktop environment" and "end 
user
+packages".  To keep things manageable, we create a _manifest_ for the desktop
+profile that can be kept in version control, and which allows us to reproduce
+the exact same environment in the future (even on a different computer!).
+
+`~/desktop-manifest.scm`:
+```scheme
+(specifications->manifest
+ '("xfce" "xfce4-session" "xfconf" "xfce4-battery-plugin"
+   "pulseaudio" "xfce4-volumed-pulse" "xfce4-notifyd"
+   ;; Helpful graphical programs.
+   "mousepad" "orage"
+   ;; System configuration utilities.
+   "xbacklight" "pavucontrol" "stow"
+   ;; For HTTPS access.
+   "nss-certs"
+   ;; These utilities are provided by the host, but we want the Guix versions
+   ;; because they are likely better integrated and up to date.
+   "fontconfig" "bash-completion" "gnupg" "man-db" "git"))
+```
+
+Create the initial profile generation:
+
+```sh
+guix package -p ~/.desktop-profile -m ~/desktop-manifest.scm
+```
+
+That installs a union of all packages listed in the manifest to
+`~/.desktop-profile`, and creates a script we will use to "activate" it later.
+To update this profile, simply invoke the same command again after running
+`guix pull` or modifying the manifest.
+
+Before XFCE can be started, we need to create a configuration file for the X
+server to ensure the host executable is used, and we will tell it to to stay
+on virtual terminal 4.  We also create a `.xinitrc` script that automatically
+starts XFCE every time `xinit` is invoked.
+
+`~/.xserverrc`:
+```sh
+exec /usr/bin/Xorg -novtswitch -nolisten tcp "$@" vt$XDG_VTNR
+```
+
+`~/.xinitrc`:
+```sh
+#!/bin/sh
+
+# Get the default xinit configuration for CentOS.
+. /etc/X11/xinit/xinitrc-common
+
+exec startxfce4
+```
+
+`.xinitrc` needs to be executable:
+
+```sh
+chmod +x ~/.xinitrc
+```
+
+Now let's activate the desktop profile and start the X server, using ":1" as
+`DISPLAY` (remember that we have another X server running on VT2, occupying the
+default ":0" display).
+
+```sh
+GUIX_PROFILE=~/.desktop-profile
+source ~/.desktop-profile/etc/profile
+xinit -- :1
+```
+
+Cool, we're in XFCE!  Let's open a terminal and install a browser & some fonts:
+
+```sh
+guix install icecat font-liberation font-dejavu
+```
+
+To make the newly installed fonts available right away we need to invoke 
`fc-cache`:
+
+```sh
+fc-cache -rv
+```
+
+Finally, we'll configure the shell to source scripts installed by Guix so that
+bash completions and similar work, by adding these lines at the end of 
`.bashrc`:
+
+`~/.bashrc`:
+```sh
+# Source the Guix shell configuration directories, for vte.sh and bash 
completions.
+GUIX_PROFILES=("${HOME}/.desktop-profile"
+               "${HOME}/.guix-profile"
+               "${HOME}/.config/guix/current")
+for profile in "${GUIX_PROFILES[@]}"; do
+    for dir in "${profile}/etc/bash_completion.d" "${profile}/etc/profile.d"; 
do
+        if [[ -d "${dir}" ]]; then
+            for f in "${dir}"/*; do
+                . $f
+            done
+        fi
+    done
+done
+```
+
+Phew!  It took some work, but by now you should have a working XFCE desktop
+environment, with bash completions and all.  If you are content with starting
+it manually, skip to "final tweaks" below.  Otherwise, read on.
+
+(If you do not have a working desktop after following these steps, please email
+address@hidden so we can adjust the tutorial!)
+
+#### Starting XFCE automatically on boot
+
+We can configure our login shell to start XFCE every time we log in to VT4 by
+adding these lines at the end of `~/.bash_profile`:
+
+```sh
+# Start Xorg on display :1 when logged in to VT4, unless DISPLAY is already 
set.
+if [[ -z "${DISPLAY}" && "${XDG_VTNR}" == 4 ]]; then
+    GUIX_PROFILE="${HOME}/.desktop-profile"
+    source "${HOME}/.desktop-profile/etc/profile"
+    exec xinit -- :1
+fi
+```
+
+To avoid the need for typing username and password at the console, instruct the
+`getty` service for TTY4 to automatically log in user 'alice':
+
+`/etc/systemd/system/getty@tty4.service.d/override.conf`:
+```
+[Unit]
+After=graphical.target
+
+[Service]
+# Delay for a few seconds, to ensure the Xorg server on VT2 starts first.
+ExecStartPre=/bin/sleep 3
+ExecStart=
+ExecStart=-/sbin/agetty --autologin alice --noclear %I $TERM
+Restart=on-success
+```
+
+Now just switching to VT4 will start XFCE!  To do this when the system boots,
+simply enable the `getty@tty4` service:
+
+```sh
+sudo systemctl enable getty@tty4.service
+```
+
+## Final tweaks
+
+Some issues were found during usage of the XFCE environment.  Launching 
programs
+from the file manager failed because `gio-launch-desktop` was unavailable, and
+xfce4-terminal complained that `__vte_prompt_command` was not found.
+
+These problems will be fixed in Guix eventually, but for now we'll work around
+them in our manifest:
+
+`~/desktop-manifest.scm`:
+```scheme
+(specifications->manifest
+ '("xfce" "xfce4-session" "xfconf" "xfce4-battery-plugin"
+   ...
+   "glib:bin"                  ;for 'gio-launch-desktop'
+   "vte"))                     ;for vte.sh, required by xfce4-terminal
+```
+
+We also found that closing the lid would not send the system to sleep, even
+though `xfce4-power-manager --dump` showed no problems.  To work around it,
+we told systemd to ignore any "inhibitors" and take care of lid handling 
itself:
+
+`/etc/systemd/logind.conf`:
+```
+HandleLidSwitch=suspend
+LidSwitchIgnoreInhibited=yes
+```
+
+Additionally it is
+[strongly 
recommended](https://guix.gnu.org/manual/en/html_node/Application-Setup.html#Name-Service-Switch-1)
+to enable the _name service cache daemon_ if not already running.  On CentOS
+this can be done by:
+
+```sh
+sudo yum install nscd
+```
+
+#### Bonus section: Installing programs with a custom build of Qt
+
+One additional issue was that Qt programs did not work due to the stock CentOS
+kernel being too old.  Specifically it lacks the `renameat2()` system call.
+Luckily Qt can be configured to not use it.  A patch has been submitted to
+Guix, but since we are in a hurry, we will add a procedure to our manifest so
+we can use Qt programs (here `wpa-supplicant-gui`) until the Guix fix is 
merged:
+
+`~/.desktop-manifest.scm`:
+```scheme
+(use-modules (guix packages)
+             (guix utils)
+             (gnu)
+             (gnu packages admin)
+             (gnu packages qt))
+
+(define qtbase/fixed
+  (package/inherit
+   qtbase
+   (arguments
+    (substitute-keyword-arguments (package-arguments qtbase)
+      ((#:phases phases)
+       `(modify-phases ,phases
+          (add-after 'unpack 'disable-renameat2
+            (lambda _
+              (substitute* "src/corelib/configure.json"
+                (("config\\.linux && tests\\.renameat2")
+                 "false"))
+              #t))))))))
+
+(define with-fixed-qt
+  ;; This procedure recursively rewrites any references to 'qtbase'
+  ;; with our patched version.
+  (package-input-rewriting `((,qtbase . ,qtbase/fixed))))
+
+(packages->manifest
+ (append (list (with-fixed-qt wpa-supplicant-gui))
+         (map specification->package
+              '("xfce" "xfce4-session" "xfconf" "xfce4-battery-plugin"
+                ...))))
+```
+
+...and now `wpa_gui` works after installing the new manifest!
+
+#### Acknowledgements
+
+Special thanks to [Ocean Space Acoustics AS](https://www.osac.no/) for 
sponsoring this work.
+
+#### About GNU Guix
+
+[GNU Guix](https://www.gnu.org/software/guix) is a transactional package
+manager and an advanced distribution of the GNU system that [respects
+user
+freedom](https://www.gnu.org/distros/free-system-distribution-guidelines.html).
+Guix can be used on top of any system running the kernel Linux, or it
+can be used as a standalone operating system distribution for i686,
+x86_64, ARMv7, and AArch64 machines.
+
+In addition to standard package management features, Guix supports
+transactional upgrades and roll-backs, unprivileged package management,
+per-user profiles, and garbage collection.  When used as a standalone
+GNU/Linux distribution, Guix offers a declarative, stateless approach to
+operating system configuration management.  Guix is highly customizable
+and hackable through [Guile](https://www.gnu.org/software/guile)
+programming interfaces and extensions to the
+[Scheme](http://schemers.org) language.