X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=0cd868ade28b70e40163bbb3ddfca44f0e536b8c;hp=fee078898cc2afaad3453bc8b22ceef18d810dcb;hb=3fe1519ec24bf096c8389fa66352d97d7d269e12;hpb=c249f66a70f9ea623205f27f7931727acbafba9e diff --git a/README b/README index fee078898..0cd868ade 100644 --- a/README +++ b/README @@ -1,95 +1,183 @@ -udev - userspace device management - -For more information see the files in the docs/ directory. - -Important Note: - Integrating udev in the system is a whole lot of work, has complex dependencies - and differs a lot from distro to distro. All reasonable distros depend on udev - these days and the system will not work without it. - - The upstream udev project does not support or recomend to replace a distro's udev - installation with the upstream version. The installation of a unmodified upstream - version may render your system unusable! There is no "default" setup or a set - of "default" rules provided by the upstream udev version. - -Requirements: - - 2.6 version of the Linux kernel. - - - The kernel must have sysfs, netlink, and hotplug enabled. - - - The proc filesystem must be mounted on /proc. - - - The sysfs filesystem must be mounted at /sys. No other location - is supported. - - -Operation: - - Udev creates and removes device nodes in /dev based on events - the kernel sends out on device discovery or removal - - - Directly after mounting the root filesystem, the udevd daemon must be - started by an init script. - - - From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should - be disabled with an init script before kernel modules are loaded. - - - During bootup, /dev usually gets a tmpfs filesystem mounted which is - populated from scratch by udev (created nodes don't survive a reboot, - the /lib/udev/devices directory should be used for "static nodes"). - - - Udev replaces the hotplug event management invoked from /sbin/hotplug - by the udevd daemon, which receives the kernel events over netlink. - - - All kernel events are matched against a set of specified rules which - make it possible to hook into the event processing. - - - Copies of the rules files for all major distros are in the etc/udev - directory (you may look there how others distros are doing it). - -Compile Options: - prefix - Set this to the default root that you want to use only override - this if you really know what you are doing even then, you probably - don't do the right thing. - DESTDIR - Prefix for install target, used for package building. - USE_LOG - if set to 'true', udev is able to pass errors or debug information - to syslog. This is very useful to see what udev is doing or not doing, - it is enabled by default. - DEBUG - If set to 'true', very verbose debugging messages will be compiled - into the udev binaries. The actual level of debugging is specified - in the udev config file. - STRIPCMD - If udev is compiled for packaging an empty string can be passed - to disable the stripping of the binaries. - USE_SELINUX - If set to 'true', udev will be built with SELinux support - enabled. This is disabled by default. - USE_KLIBC - If set to 'true', udev is built and linked against klibc. - Default value is 'false'. KLCC specifies the klibc compiler - wrapper, usually located at /usr/bin/klcc. - EXTRAS - If set, will build the "extra" helper programs as specified - as listed (see below for an example). - -If you want to build the udev helper program cdrom_id and scsi_id: - make EXTRAS="extras/cdrom_id extras/scsi_id" - -Installation: - - The install target intall the udev binaries in the default locations, - all at boot time reqired binaries will be installed in /sbin. - - - The default location for scripts and binaries that are called from - rules is /lib/udev. - - - It is recommended to use the /lib/udev/devices directory to place - device nodes and symlinks in, which are copied to /dev at every boot. - That way, nodes for broken subsystems or devices which can't be - detected automatically by the kernel will always be available. - -Please direct any comment/question/concern to the linux-hotplug-devel mailing list at: - linux-hotplug-devel@lists.sourceforge.net +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/elogind/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/elogind/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 , so like instead +of . + +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, hibernate, +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. + +Elogind and the running cgroup controller +----------------------------------------- +While 'configure' runs, it will detect which controller is in place. +If no controller is in place, configure will determine, that elogind +should be its own controller, which will be a very limited one. + +This approach should generally work, but if you just have no cgroup +controller in place, yet, or if you are currently switching to +another one, this approach will fail. + +In this case you can do one of the two following things: + + 1) Boot your system with the target init system and cgroup + controller, before configuring and building elogind, or + 2) Use the --with-cgroup-controller=name option. + +Example: If you plan to use openrc, but openrc has not yet booted + the machine, you can use + --with-cgroup-controller=openrc + to let elogind know that openrc will be the controller + in charge. + +However, if you set the controller at configure time to something +different than what is in place, elogind will not start until that +controller is actively used as the primary controller. + +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)