Introduction to elogind
elogind is the systemd project's "logind", extracted to be a standalone daemon. It integrates with Linux-PAM-1.6.0 to track all the users logged in to a system, and whether they are logged in graphically, on the console, or remotely. Elogind exposes this information via the standard org.freedesktop.login1 D-Bus interface, and also through the file system using systemd's standard /run/systemd
layout.
Note
Development versions of BLFS may not build or run some packages properly if LFS or dependencies have been updated since the most recent stable versions of the books.
Package Information
elogind Dependencies
Recommended
dbus-1.14.10 (runtime), Linux-PAM-1.6.0 (required for Xorg), Polkit-124 (runtime), docbook-xml-4.5, docbook-xsl-nons-1.79.2, and libxslt-1.1.39 (all three to build the man pages)
Optional
lxml-4.9.4, zsh-5.9, Valgrind-3.22.0 (needed for tests), audit-userspace, bash-completion, kexec, and SELinux
Editor Notes: https://wiki.linuxfromscratch.org/blfs/wiki/Logind
Kernel Configuration
Enable the following options in the kernel configuration and recompile the kernel if necessary:
File systems --->
[*] Inotify support for userspace [INOTIFY_USER]
Pseudo filesystems --->
[*] Tmpfs virtual memory file system support (former shm fs) [TMPFS]
[*] Tmpfs POSIX Access Control Lists [TMPFS_POSIX_ACL]
In addition, some tests need the userspace cryptographic kernel API, which is enabled with:
-*- Cryptographic API ---> [CRYPTO]
Crypto core or helper --->
<*/M> Userspace cryptographic algorithm configuration [CRYPTO_USER]
Userspace interface --->
<*/M> Hash algorithms [CRYPTO_USER_API_HASH]
Installation of elogind
Install elogind by running the following commands:
mkdir build &&
cd build &&
meson setup .. \
--prefix=/usr \
--buildtype=release \
-Dman=auto \
-Ddocdir=/usr/share/doc/elogind-252.9 \
-Dcgroup-controller=elogind \
-Ddev-kvm-mode=0660 \
-Ddbuspolicydir=/etc/dbus-1/system.d &&
ninja
To test the results, issue: ninja test. A few tests are skipped if not run with root
privileges. Two tests named test-fs-util
and test-id128
require the /etc/machine-id
symlink, so they will fail if this symlink is not created following the instruction in dbus-1.14.10 yet.
Now, as the root
user:
ninja install &&
ln -sfv libelogind.pc /usr/lib/pkgconfig/libsystemd.pc &&
ln -sfvn elogind /usr/include/systemd
Command Explanations
-Ddocdir=/usr/share/doc/elogind-252.9
: This is needed to install documentation in a versioned directory.
-Dcgroup-controller=elogind
: This switch is necessary to build this package when the kernel is not built with CONFIG_CGROUPS
enabled. Note that elogind strictly needs a kernel with CONFIG_CGROUPS
enabled at runtime, but this switch will allow building the package first.
-Ddbuspolicydir=/etc/dbus-1/system.d
: This switch sets the location of the D-Bus policy directory.
-Ddev-kvm-mode=0660
: The LFS udev rule sets the mode of /dev/kvm
to 0660. This option ensures the elogind udev rules consistent with the LFS configuration.
-Dman=auto
: The default value of this switch is false. Setting it to auto allows building and installing the man pages if the recommended dependencies are installed.
-Dhtml=auto
: The default value of this switch is false. Setting it to auto allows building and installing the html documentation if the recommended dependencies are installed.
-Ddefault-kill-user-processes=false
: Determines whether the processes of a user should be killed when the user logs out. The default is true, but this defeats the traditional use of screen or tmux. This can also be changed in the configuration file (see below).
ln -s ...: These commands install symlinks so that software packages can find the systemd-compatible library and headers.
Configuring elogind
Config File
/etc/elogind/logind.conf
Configuration Information
The installed file /etc/elogind/logind.conf
contains all the possible options with their defaults, commented out. You may wish to disable automatically killing user processes when the user logs out, by running, as the root
user:
sed -e '/\[Login\]/a KillUserProcesses=no' \
-i /etc/elogind/logind.conf
Each user will need to register a user session using Linux-PAM at login. The /etc/pam.d/system-session
file needs to be modified and a new file must be created in order for elogind to work correctly. Run the following commands as the root
user:
cat >> /etc/pam.d/system-session << "EOF" &&
# Begin elogind addition
session required pam_loginuid.so
session optional pam_elogind.so
# End elogind addition
EOF
cat > /etc/pam.d/elogind-user << "EOF"
# Begin /etc/pam.d/elogind-user
account required pam_access.so
account include system-account
session required pam_env.so
session required pam_limits.so
session required pam_unix.so
session required pam_loginuid.so
session optional pam_keyinit.so force revoke
session optional pam_elogind.so
auth required pam_deny.so
password required pam_deny.so
# End /etc/pam.d/elogind-user
EOF
Contents
Installed Programs: busctl, elogind-inhibit, and loginctl
Installed Library: libelogind.so
Installed Directories: /usr/lib/elogind, /etc/elogind, /usr/include/elogind, and /usr/share/doc/elogind-252.9
Short Descriptions
busctl
|
is used to introspect and monitor the D-Bus bus
|
elogind-inhibit
|
is used to execute a program with a shutdown, sleep or idle inhibitor lock taken
|
loginctl
|
is used to introspect and control the state of the elogind Login Manager
|
libelogind.so
|
is the main elogind utility library
|