26. Display Managers

Display Managers are graphical programs used for starting the graphical display (currently, the X server) and providing a login capability for a Window Manager or Desktop Environment.

There are many Display Managers available. Some of the more well known include: GDM, KDM (deprecated), LightDM, LXDM, Slim, and SDDM.

Among the Desktop Environments available for Linux you find: Enlightenment, GNOME, KDE, LXDE, LXQt, and XFce.

Choosing a Display Manager or Desktop Environment is highly subjective. The choice depends on the look and feel of the packages, the resources (memory and disk space) required, and the utilities included.

In this chapter, the installation instructions of some Display Managers are presented. Later in the book, you will find other ones, which are provided as part of some Desktop Environments.

26.1 GDM-43.0

Introduction to GDM

GDM is a system service that is responsible for providing graphical logins and managing local and remote displays.

This package is known to build and work properly using an LFS 11.3 platform.

Package Information

Download (HTTP): https://download.gnome.org/sources/gdm/43/gdm-43.0.tar.xz
Download (FTP): ftp://ftp.acc.umu.se/pub/gnome/sources/gdm/43/gdm-43.0.tar.xz
Download MD5 sum: d9ca2abdf2359d0420dc71a1bd1d7530
Download size: 812 KB
Estimated disk space required: 33 MB
Estimated build time: 0.3 SBU

GDM Dependencies

Installation of GDM

It is recommended to have a dedicated user and group to take control of the gdm daemon after it is started. Issue the following commands as the root user:

groupadd -g 21 gdm &&
useradd -c "GDM Daemon Owner" -d /var/lib/gdm -u 21 \
        -g gdm -s /bin/false gdm &&
passwd -ql gdm

Install GDM by running the following commands:

mkdir build &&
cd    build &&

meson --prefix=/usr               \
      --buildtype=release         \
      -Dgdm-xsession=true         \
      -Drun-dir=/run/gdm ..
ninja

This package does not come with a usable test suite.

Now, as the root user:

ninja install

Command Explanations

--buildtype=release: Specify a buildtype suitable for stable releases of the package, as the default may produce unoptimized binaries.

-Dinitial-vt=7: Use this switch to make GDM start on VT7 instead of the first free VT.

-Ddefault-pam-config=lfs: Use this switch if you did not create the /etc/lfs-release file or distribution auto detection will fail and you will be unable to use GDM.

-Dgdm-xsession=true: This enables the installation of the GDM Xsession file.

Configuring GDM

Config Files

/etc/gdm/custom.conf

Configuration Information

The GDM daemon is configured using the /etc/gdm/custom.conf file. Default values are stored in GSettings in the gdm.schemas file. It is recommended that end-users modify the /etc/gdm/custom.conf file because the schemas file may be overwritten when the user updates their system to have a newer version of GDM.

Systemd Unit

To start the gdm daemon at boot, enable the previously installed systemd unit by running the following command as the root user:

systemctl enable gdm

Installed Programs: gdm, gdmflexiserver, and gdm-screenshot

Installed Libraries: libgdm.so and pam_gdm.so (PAM Module)

Installed Directories: /etc/gdm, /usr/include/gdm, /usr/share/gdm, and /usr/share/help/*/gdm

Short Descriptions

gdm is a login prompt for GNOME

gdm-screenshot is a screenshot tool for GDM.

26.2 lightdm-1.32.0

Introduction to Lightdm

The lightdm package contains a lightweight display manager based upon GTK.

This package is known to build and work properly using an LFS 11.3 platform.

Lightdm Package Information

Download (HTTP): https://github.com/CanonicalLtd/lightdm/releases/download/1.32.0/lightdm-1.32.0.tar.xz
Download MD5 sum: e62a5da6c35f612e4d9575eda5c8d467
Download size: 508 KB
Estimated disk space required: 20 MB
Estimated build time: 0.2 SBU

Additional download

Note

The greeter is a program to present a graphical login screen. There are several alternative greeters, but the gtk+ package is the reference implementation. For a list of other greeters, see https://en.wikipedia.org/wiki/LightDM.

Download (HTTP): https://github.com/Xubuntu/lightdm-gtk-greeter/releases/download/lightdm-gtk-greeter-2.0.8/lightdm-gtk-greeter-2.0.8.tar.gz
Download MD5 sum: 373c73c67367df511eb544e09a2da281
Download size: 569.7 KB
Estimated disk space required: 5.5 MB
Estimated build time: less than 0.1 SBU

Lightdm Dependencies

Required

Exo-4.18.0 (for the greeter), libgcrypt-1.10.1, itstool-2.0.7, Linux-PAM-1.5.2, and Xorg-Server-21.1.7 (Runtime)

Optional

AccountsService-22.08.8 (run time), at-spi2-core-2.46.0, GTK-Doc-1.33.2, Qt-5.15.8, libido, and libindicator

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/lightdm

Installation of Lightdm

First, create a dedicated user and group to take control of the lightdm daemon after it is started. Issue the following commands as the root user:

groupadd -g 65 lightdm       &&
useradd  -c "Lightdm Daemon" \
         -d /var/lib/lightdm \
         -u 65 -g lightdm    \
         -s /bin/false lightdm

Install lightdm by running the following commands:

./configure --prefix=/usr                 \
            --libexecdir=/usr/lib/lightdm \
            --localstatedir=/var          \
            --sbindir=/usr/bin            \
            --sysconfdir=/etc             \
            --disable-static              \
            --disable-tests               \
            --with-greeter-user=lightdm   \
            --with-greeter-session=lightdm-gtk-greeter \
            --docdir=/usr/share/doc/lightdm-1.32.0 &&
make

This package does not come with a test suite.

Now, as the root user:

make install                                                  &&
cp tests/src/lightdm-session /usr/bin                         &&
sed -i '1 s/sh/bash --login/' /usr/bin/lightdm-session        &&
rm -rf /etc/init                                              &&
install -v -dm755 -o lightdm -g lightdm /var/lib/lightdm      &&
install -v -dm755 -o lightdm -g lightdm /var/lib/lightdm-data &&
install -v -dm755 -o lightdm -g lightdm /var/cache/lightdm    &&
install -v -dm770 -o lightdm -g lightdm /var/log/lightdm

Now build the greeter:

tar -xf ../lightdm-gtk-greeter-2.0.8.tar.gz &&
cd lightdm-gtk-greeter-2.0.8 &&

./configure --prefix=/usr                 \
            --libexecdir=/usr/lib/lightdm \
            --sbindir=/usr/bin            \
            --sysconfdir=/etc             \
            --with-libxklavier            \
            --enable-kill-on-sigterm      \
            --disable-libido              \
            --disable-libindicator        \
            --disable-static              \
            --disable-maintainer-mode     \
            --docdir=/usr/share/doc/lightdm-gtk-greeter-2.0.8 &&
make

Now, as the root user:

make install

Note

If you installed Xorg in /opt, you will need to create a symbolic link so lightdm can find the Xorg server. As the root user:

ln -sf /opt/xorg/bin/Xorg /usr/bin/X

Command Explanations

sed … /usr/bin/lightdm-session: This command ensures that the initial login via the greeter sources /etc/profile and ~/.bash_profile. Without this, commands that depend on different environment variables may not work as expected.

Configuring lightdm

###

Config Files

/etc/lightdm/{lightdm,users,keys}.conf

###

Systemd Unit

Install the lightdm.service unit included in the blfs-systemd-units-20220720 package:

make install-lightdm

Available Sessions

The greeter offers a list of available sessions, depending on the Window Managers and Desktop Environments installed. The list includes sessions which have a corresponding .desktop file installed under /usr/share/xsessions. Most of the Window Managers and Desktop Environments automatically provide those files, but if necessary, you may include a custom one.

Installed Programs: dm-tool, lightdm, and lightdm-gtk-greeter

Installed Libraries: liblightdm-gobject-1.so

Installed Directories: /etc/lightdm, /etc/apparmor.d, /usr/lib/lightdm, /usr/include/lightdm-gobject-1, /usr/share/help/C/lightdm /usr/share/gtk-doc/html/lightdm-gobject-1, /usr/share/doc/lightdm-gtk-greeter-2.0.8, /var/lib/lightdm, /var/lib/lightdm-data, /var/cache/lightdm, and /var/log/lightdm

Short Descriptions

lightdm is a display and login manager

lightdm-gtk-greeter is an auxiliary process that displays the greeter, a graphical user interface that performs user authentication and initiates the selected window manager or display environment.

26.3 lxdm-0.5.3

Introduction to LXDM

The LXDM is a lightweight Display Manager for the LXDE desktop. It can also be used as an alternative to other Display Managers such as GNOME’s GDM or LightDM.

This package is known to build and work properly using an LFS 11.3 platform.

Note

The lxdm display manager does not support wayland based window managers such as plasma-wayland or gnome-wayland.

Package Information

Download (HTTP): https://downloads.sourceforge.net/lxdm/lxdm-0.5.3.tar.xz
Download MD5 sum: 061caae432634e6db38bbdc84bc6ffa0
Download size: 236 KB
Estimated disk space required: 5.6 MB
Estimated build time: less than 0.1 SBU

LXDM Dependencies

Required

GTK+-2.24.33, ISO Codes-4.12.0, and librsvg-2.54.5 (runtime, for default theme background)

Optional

GTK+-3.24.36

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/lxdm

Installation of LXDM

First, some fixes.

cat > pam/lxdm << "EOF"
# Begin /etc/pam.d/lxdm

auth     requisite      pam_nologin.so
auth     required       pam_env.so
auth     required       pam_succeed_if.so uid >= 1000 quiet
auth     include        system-auth

account  include        system-account

password include        system-password

session  required       pam_limits.so
session  include        system-session

# End /etc/pam.d/lxdm
EOF

sed -i 's:sysconfig/i18n:profile.d/i18n.sh:g' data/lxdm.in &&
sed -i 's:/etc/xprofile:/etc/profile:g' data/Xsession &&
sed -e 's/^bg/#&/'        \
    -e '/reset=1/ s/# //' \
    -e 's/logou$/logout/' \
    -e "/arg=/a arg=$XORG_PREFIX/bin/X" \
    -i data/lxdm.conf.in

Install LXDM by running the following commands:

./configure --prefix=/usr     \
            --sysconfdir=/etc \
            --with-pam        \
            --with-systemdsystemunitdir=/lib/systemd/system &&
make

This package does not come with a test suite.

Now, as the root user:

make install

Command Explanations

cat > pam/lxdm « “EOF” …: Replace default /etc/pam.d/lxdm by another one appropriate for BLFS.

sed -i … data/lxdm.conf.in: Modifications in the default configuration: (1) fix the background to the default one; (2) restart X when session is close; (3) typo; and (4) include XORG_PREFIX, which may be different from /usr.

sed -i … data/Xsession: Source /etc/profile, instead of other file, according to BLFS standard.

sed -i … data/lxdm.in: Fix greeter’s locale for BLFS specification.

--with-pam: This parameter enables use of pam authentication.

Configuring LXDM

Config Files

/etc/lxdm/lxdm.conf

Systemd Unit

To start LXDM at boot execute the following command as the root user:

systemctl enable lxdm

Configuration Information

The LXDM daemon configuration file (/etc/lxdm/lxdm.conf) specifies options that include numlock on/off, background image (bg), session, etc. You can set a default session by uncommenting the line: session=/usr/bin/startlxde and replacing startlxde with your session of choice. For GNOME session=/usr/bin/gnome-session. For OPENBOX session=/usr/bin/openbox-session and for XFCE session=/usr/bin/startxfce4.

It is also possible to set the preferred session on a per-user basis by editing the ~/.dmrc file for each user and adding:

[Desktop]
        Session=xfce

You can replace the default dummy face in the greeting screen by another image representing your user. For that, copy or symlink the desired image to your home directory with the name .face.

Installed Programs: lxdm, lxdm-binary and lxdm-config

Installed Libraries: None

Installed Directories: /etc/lxdm and /usr/share/lxdm

Short Descriptions

lxdm is a script to execute lxdm-binary

lxdm-binary is the actual Display Manager; needs to be executed with option -d to daemonize

lxdm-config is a graphical customizing program.

26. Display Managers

26.1 GDM-43.0

Introduction to GDM

Package Information

GDM Dependencies

Required

Optional

Runtime Dependencies

Installation of GDM

Command Explanations

Configuring GDM

Config Files

Configuration Information

Systemd Unit

Contents

Short Descriptions

26.2 lightdm-1.32.0

Introduction to Lightdm

Lightdm Package Information

Additional download

Note

Lightdm Dependencies

Required

Recommended

Optional

Installation of Lightdm

Note

Command Explanations

Configuring lightdm

Config Files

Systemd Unit

Available Sessions

Contents

Short Descriptions

26.3 lxdm-0.5.3

Introduction to LXDM

Note

Package Information

LXDM Dependencies

Required

Recommended

Optional

Installation of LXDM

Command Explanations

Configuring LXDM

Config Files

Systemd Unit

Configuration Information

Contents

Short Descriptions