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| Elogind User, Seat and Session Manager | |
| Introduction | |
| ------------ | |
| Elogind is the systemd project's "logind", extracted out to be a | |
| standalone daemon. It integrates with PAM to know the set of users | |
| that are 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, | |
| as well as through the file system using systemd's standard | |
| /run/systemd layout. Elogind also provides "libelogind", which is a | |
| subset of the facilities offered by "libsystemd". There is a | |
| "libelogind.pc" pkg-config file as well. | |
| All of the credit for elogind should go to the systemd developers. | |
| For more on systemd, see | |
| http://www.freedesktop.org/wiki/Software/systemd. All of the blame | |
| should go to Andy Wingo, who extracted elogind from systemd. | |
| Contributing | |
| ------------ | |
| Elogind was branched from systemd version 219, and preserves the git | |
| history of the systemd project. The version of elogind is the | |
| upstream systemd version, followed by the patchlevel of elogind. For | |
| example version 219.12 is the twelfth elogind release, which aims to | |
| provide a subset of the interfaces of systemd 219. | |
| To contribute to elogind, fork the current source code from github: | |
| https://github.com/wingo/elogind | |
| Send a pull request for the changes you like. | |
| To chat about elogind: | |
| #guix on irc.freenode.org | |
| Finally, bug reports: | |
| https://github.com/wingo/elogind/issues | |
| Why bother? | |
| ----------- | |
| Elogind has been developed for use in GuixSD, the OS distribution of | |
| GNU Guix. See http://gnu.org/s/guix for more on Guix. GuixSD uses a | |
| specific init manager (DMD), for reasons that are not relevant here, | |
| but still aims to eventually be a full-featured distribution that can | |
| run GNOME and other desktop environments. However, to run GNOME these | |
| days means that you need to have support for the login1 D-Bus | |
| interface, which is currently only provided by systemd. That is the | |
| origin of this project: to take the excellent logind functionality | |
| from systemd and provide it as a standalone package. | |
| We like systemd. We realize that there are people out there that hate | |
| it. You're welcome to use elogind for whatever purpose you like -- | |
| as-is, or as a jumping-off point for other things -- but please don't | |
| use it as part of some anti-systemd vendetta. Systemd hackers are | |
| smart folks that are trying to solve interesting problems on the free | |
| desktop, and their large adoption is largely because they solve | |
| problems that users and developers of user-focused applications care | |
| about. We are appreciative of their logind effort and think that | |
| everyone deserves to run it if they like, even if they use a different | |
| PID 1. | |
| Differences relative to systemd | |
| ------------------------------- | |
| The pkg-config file is called libelogind, not libsystemd or | |
| libsystemd-logind. | |
| The headers are in <elogind/...>, so like <elogind/sd-login.h> instead | |
| of <systemd/sd-login.h>. | |
| Libelogind just implements login-related functionality. It also | |
| provides the sd-bus API. | |
| Unlike systemd, whose logind arranges to manage resources for user | |
| sessions via RPC calls to systemd, in elogind there is no systemd so | |
| there is no global cgroup-based resource management. This has a few | |
| implications: | |
| * Elogind does not create "slices" for users. Elogind will not | |
| record that users are associated with slices. | |
| * The /run/systemd/slices directory will always be empty. | |
| * Elogind does not have the concept of a "scope", internally, as | |
| it's the same as a session. Any API that refers to scopes will | |
| always return an error code. | |
| On the other hand, elogind does use a similar strategy to systemd in | |
| that it places processes in a private cgroup for organizational | |
| purposes, without installing any controllers (see | |
| http://0pointer.de/blog/projects/cgroups-vs-cgroups.html). This | |
| allows elogind to map arbitrary processes to sessions, even if the | |
| process does the usual double-fork to be reparented to PID 1. | |
| Elogind does not manage virtual terminals. | |
| Elogind does monitor power button and the lid switch, like systemd, | |
| but instead of doing RPC to systemd to suspend, poweroff, or restart | |
| the machine, elogind just does this directly. For suspend, hybernate, | |
| and hybrid-sleep, elogind uses the same code as systemd-sleep. | |
| Instead of using a separate sleep.conf file to configure the sleep | |
| behavior, this is included in the [Sleep] section of | |
| /etc/elogind/login.conf. See the example login.conf for more. For | |
| shutdown, reboot, and kexec, elogind shells out to "halt", "reboot", | |
| and "kexec" binaries. | |
| The loginctl command has the poweroff, reboot, sleep, hibernate, and | |
| hybrid-sleep commands from systemd, as well as the --ignore-inhibitors | |
| flag. | |
| The PAM module is called pam_elogind.so, not pam_systemd.so. | |
| License | |
| ------- | |
| LGPLv2.1+ for all code | |
| - except src/shared/MurmurHash2.c which is Public Domain | |
| - except src/shared/siphash24.c which is CC0 Public Domain | |
| - except src/journal/lookup3.c which is Public Domain | |
| Dependencies | |
| ------------ | |
| glibc >= 2.14 | |
| libcap | |
| libmount >= 2.20 (from util-linux) | |
| libseccomp >= 1.0.0 (optional) | |
| libblkid >= 2.24 (from util-linux) (optional) | |
| PAM >= 1.1.2 (optional) | |
| libacl (optional) | |
| libselinux (optional) | |
| make, gcc, and similar tools | |
| During runtime, you need the following additional dependencies: | |
| dbus >= 1.4.0 (strictly speaking optional, but recommended) | |
| PolicyKit (optional) | |
| When building from git, you need the following additional | |
| dependencies: | |
| pkg-config | |
| docbook-xsl | |
| xsltproc | |
| automake | |
| autoconf | |
| libtool | |
| intltool | |
| gperf | |
| gtkdocize (optional) |