systemd中文文档

- 启动: http://systemd.cn/docs/Booting/
- 自动启动评估: http://systemd.cn/docs/Booting/AUTOMATIC_BOOT_ASSESSMENT/
- 启动组件和根文件系统探测: http://systemd.cn/docs/Booting/ROOTFS_DISCOVERY/
- 引导加载程序接口: http://systemd.cn/docs/Booting/BOOT_LOADER_INTERFACE/
- 恢复出厂设置: http://systemd.cn/docs/Booting/FACTORY_RESET/
- 挂载点可用性要求: http://systemd.cn/docs/Booting/MOUNT_REQUIREMENTS/
- TPM2 PCR测量: http://systemd.cn/docs/Booting/TPM2_PCR_MEASUREMENTS/
- Boot Loader Specification: http://systemd.cn/docs/BOOT_LOADER_SPECIFICATION/
- Discoverable Partitions: http://systemd.cn/docs/DISCOVERABLE_PARTITIONS/
- Elf Dlopen Metadata: http://systemd.cn/docs/ELF_DLOPEN_METADATA/
- Osc Context: http://systemd.cn/docs/OSC_CONTEXT/
- Package Metadata for Executable Files: http://systemd.cn/docs/PACKAGE_METADATA_FOR_EXECUTABLE_FILES/
- API File Systems: http://systemd.cn/docs/API_FILE_SYSTEMS/
- Appstream Bundle: http://systemd.cn/docs/APPSTREAM_BUNDLE/
- Backports: http://systemd.cn/docs/BACKPORTS/
- Booting Without /usr is Broken: http://systemd.cn/docs/SEPARATE_USR_IS_BROKEN/
- Code Quality Tools: http://systemd.cn/docs/CODE_QUALITY/
- Coding Style: http://systemd.cn/docs/CODING_STYLE/
- Compatibility with SysV: http://systemd.cn/docs/INCOMPATIBILITIES/
- Container Interface: http://systemd.cn/docs/CONTAINER_INTERFACE/
- Contributing: http://systemd.cn/docs/CONTRIBUTING/
- Control Group APIs and Delegation: http://systemd.cn/docs/CGROUP_DELEGATION/
- Converting Existing Users to systemd-homed: http://systemd.cn/docs/CONVERTING_TO_HOMED/
- Credentials: http://systemd.cn/docs/CREDENTIALS/
- Desktop Environment Integration: http://systemd.cn/docs/DESKTOP_ENVIRONMENTS/
- Diagnosing Boot Problems: http://systemd.cn/docs/DEBUGGING/
- File Descriptor Store: http://systemd.cn/docs/FILE_DESCRIPTOR_STORE/
- Frequently Asked Questions: http://systemd.cn/docs/FAQ/
- Governance: http://systemd.cn/docs/GOVERNANCE/
- Hacking on systemd: http://systemd.cn/docs/HACKING/
- Home Directories: http://systemd.cn/docs/HOME_DIRECTORY/
- Inhibitor Locks: http://systemd.cn/docs/INHIBITOR_LOCKS/
- Initrd Interface: http://systemd.cn/docs/INITRD_INTERFACE/
- Journal Export Formats: http://systemd.cn/docs/JOURNAL_EXPORT_FORMATS/
- Journal File Format: http://systemd.cn/docs/JOURNAL_FILE_FORMAT/
- Journal Message Catalogs: http://systemd.cn/docs/CATALOG/
- JSON Group Records: http://systemd.cn/docs/GROUP_RECORD/
- JSON User Records: http://systemd.cn/docs/USER_RECORD/
- Known Environment Variables: http://systemd.cn/docs/ENVIRONMENT/
- Locking Block Device Access: http://systemd.cn/docs/BLOCK_DEVICE_LOCKING/
- Minimal Builds: http://systemd.cn/docs/MINIMAL_BUILDS/
- My Service Can't Get Realtime!: http://systemd.cn/docs/MY_SERVICE_CANT_GET_REALTIME/
- Native Journal Protocol: http://systemd.cn/docs/JOURNAL_NATIVE_PROTOCOL/
- New Control Group Interfaces: http://systemd.cn/docs/CONTROL_GROUP_INTERFACE/
- Notes for Translators: http://systemd.cn/docs/TRANSLATORS/
- Password Agents: http://systemd.cn/docs/PASSWORD_AGENTS/
- Pax Controla Groupiana: http://systemd.cn/docs/PAX_CONTROL_GROUPS/
- Portability and Stability: http://systemd.cn/docs/PORTABILITY_AND_STABILITY/
- Portable Services Introduction: http://systemd.cn/docs/PORTABLE_SERVICES/
- Porting systemd To New Distributions: http://systemd.cn/docs/DISTRO_PORTING/
- Porting to New Architectures: http://systemd.cn/docs/PORTING_TO_NEW_ARCHITECTURES/
- Predictable Network Interface Names: http://systemd.cn/docs/PREDICTABLE_INTERFACE_NAMES/
- Presets: http://systemd.cn/docs/PRESET/
- Project IDs for Disk Quotas on Exec Directories: http://systemd.cn/docs/DISK-QUOTAS-PROJECTIDS/
- Random Seeds: http://systemd.cn/docs/RANDOM_SEEDS/
- Reporting of Security Vulnerabilities: http://systemd.cn/docs/SECURITY/
- Resource Pressure Handling: http://systemd.cn/docs/PRESSURE/
- Running Services After the Network Is Up: http://systemd.cn/docs/NETWORK_ONLINE/
- Safely Building Images: http://systemd.cn/docs/BUILDING_IMAGES/
- Socket Activation with Popular Daemons: http://systemd.cn/docs/DAEMON_SOCKET_ACTIVATION/
- Steps to a Successful Release: http://systemd.cn/docs/RELEASE/
- Storage Daemons for the Root File System: http://systemd.cn/docs/ROOT_STORAGE_DAEMONS/
- systemd Community Conduct Guidelines: http://systemd.cn/docs/CODE_OF_CONDUCT/
- systemd Coredump Handling: http://systemd.cn/docs/COREDUMP/
- systemd File Hierarchy Requirements: http://systemd.cn/docs/SYSTEMD_FILE_HIERARCHY_REQUIREMENTS/
- systemd Optimizations: http://systemd.cn/docs/OPTIMIZATIONS/
- systemd Repository Architecture: http://systemd.cn/docs/ARCHITECTURE/
- systemd-boot UEFI Boot Manager: http://systemd.cn/docs/BOOT/
- systemd-homed and JSON User/Group Record Support in Desktop Environments: http://systemd.cn/docs/USERDB_AND_DESKTOPS/
- systemd-resolved and VPNs: http://systemd.cn/docs/RESOLVED-VPNS/
- Testing systemd Using Sanitizers: http://systemd.cn/docs/TESTING_WITH_SANITIZERS/
- The Case for the /usr Merge: http://systemd.cn/docs/THE_CASE_FOR_THE_USR_MERGE/
- Tips And Tricks: http://systemd.cn/docs/TIPS_AND_TRICKS/
- User Record Blob Directories: http://systemd.cn/docs/USER_RECORD_BLOB_DIRS/
- User/Group Name Syntax: http://systemd.cn/docs/USER_NAMES/
- User/Group Record Lookup API via Varlink: http://systemd.cn/docs/USER_GROUP_API/
- Users, Groups, UIDs and GIDs on systemd Systems: http://systemd.cn/docs/UIDS-GIDS/
- Using /tmp/ and /var/tmp/ Safely: http://systemd.cn/docs/TEMPORARY_DIRECTORIES/
- Varlink API Style: http://systemd.cn/docs/VARLINK/
- VM Interface: http://systemd.cn/docs/VM_INTERFACE/
- What Settings Are Currently Available For Transient Units?: http://systemd.cn/docs/TRANSIENT-SETTINGS/
- Writing Desktop Environments: http://systemd.cn/docs/WRITING_DESKTOP_ENVIRONMENTS/
- Writing Display Managers: http://systemd.cn/docs/WRITING_DISPLAY_MANAGERS/
- Writing Network Configuration Managers: http://systemd.cn/docs/WRITING_NETWORK_CONFIGURATION_MANAGERS/
- Writing Resolver Clients: http://systemd.cn/docs/WRITING_RESOLVER_CLIENTS/
- Writing syslog Daemons Which Cooperate Nicely With systemd: http://systemd.cn/docs/SYSLOG/
- Writing VM and Container Managers: http://systemd.cn/docs/WRITING_VM_AND_CONTAINER_MANAGERS/


# Writing Display Managers

_Or: How to hook up your favorite X11 display manager with systemd_

systemd's logind service obsoletes ConsoleKit which was previously widely used on Linux distributions.
For X11 display managers the switch to logind requires a minimal amount of porting, however brings a couple of new features:
true automatic multi-seat support, proper tracking of session processes, (optional) automatic killing of user processes on logout, a synchronous low-level C API and much simplification.

This document should be read together with [Writing Desktop Environments](/WRITING_DESKTOP_ENVIRONMENTS) which focuses on the porting work necessary for desktop environments.

If required it is possible to implement ConsoleKit and systemd-logind support in the same display manager, detecting at runtime which interface is needed.
The [sd_booted()](https://www.freedesktop.org/software/systemd/man/latest/sd_booted.html) call may be used to determine at runtime whether systemd is used.

To a certain level ConsoleKit and systemd-logind may be used side-by-side, but a number of features are not available if ConsoleKit is used, for example automatic multi-seat support.

Please have a look at the [Bus API of logind](https://www.freedesktop.org/software/systemd/man/latest/org.freedesktop.login1.html) and the C API as documented in [sd-login(7)](https://www.freedesktop.org/software/systemd/man/latest/sd-login.html).
(Also see below)

Minimal porting (without multi-seat) requires the following:

1. Remove/disable all code responsible for registering your service with ConsoleKit.
2. Make sure to register your greeter session via the PAM session stack, and make sure the PAM session modules include pam_systemd.
   Also, make sure to set the session class to "greeter." This may be done by setting the environment variable XDG_SESSION_CLASS to "greeter" with pam_misc_setenv() or setting the "class=greeter" option in the pam_systemd module, in order to allow applications to filter out greeter sessions from normal login sessions.
3. Make sure to register your logged in session via the PAM session stack as well, also including pam_systemd in it.
4. Optionally, use pam_misc_setenv() to set the environment variables XDG_SEAT and XDG_VTNR.
   The former should contain "seat0", the latter the VT number your session runs on. pam_systemd can determine these values automatically but it's nice to pass these variables anyway.
In summary: porting a display manager from ConsoleKit to systemd primarily means removing code, not necessarily adding any new code. Here, a cheers to simplicity!

1. Subscribe to seats showing up and going away, via the systemd-logind D-Bus interface's SeatAdded and SeatRemoved signals.
   Take possession of each seat by spawning your greeter on it.
   However, do so exclusively for seats where the boolean CanGraphical property is true.
   Note that there are seats that cannot do graphical, and there are seats that are text-only first, and gain graphical support later on.
   Most prominently this is actually seat0 which comes up in text mode, and where the graphics driver is then loaded and probed during boot.
   This means display managers must watch PropertyChanged events on all seats, to see if they gain (or lose) the CanGraphical field.
2. Use ListSeats() on the D-Bus interface to acquire a list of already available seats and also take possession of them.
3. For each seat you spawn a greeter/user session on use the XDG_SEAT and XDG_VTNR PAM environment variables to inform pam_systemd about the seat name, resp.
   VT number you start them on. Note that only the special seat "seat0" actually knows kernel VTs, so you shouldn't pass the VT number on any but the main seat, since it doesn't make any sense there.
4. Pass the seat name to the X server you start via the -seat parameter.
5. At this time X interprets the -seat parameter natively only for input devices, not for graphics devices.
   To work around this limitation we provide a tiny wrapper /lib/systemd/systemd-multi-seat-x which emulates the enumeration for graphics devices too.
   This wrapper will eventually go away, as soon as X learns udev-based graphics device enumeration natively, instead of the current PCI based one.
   Hence it is a good idea to fall back to the real X when this wrapper is not found.
   You may use this wrapper exactly like the real X server, and internally it will just exec() it after putting together a minimal multi-seat configuration.
   And that's already it.

While most information about seats, sessions and users is available on systemd-logind's D-Bus interface, this is not the only API.
The synchronous [sd-login(7)](https://www.freedesktop.org/software/systemd/man/latest/sd-login.html) C interface is often easier to use and much faster too.
In fact it is possible to implement the scheme above entirely without D-Bus relying only on this API.
Note however, that this C API is purely passive, and if you want to execute an actually state changing operation you need to use the bus interface (for example, to switch sessions, or to kill sessions and suchlike).
Also have a look at the [logind Bus API](https://www.freedesktop.org/software/systemd/man/latest/org.freedesktop.login1.html).