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--- jaysnote:systemd [2018/11/12 16:41]
jaylee
+++ jaysnote:systemd [2019/01/29 12:47]
jaylee
@@ 行 1: / 行 1: @@
-<markdown>
+ <markdown>
 # systemd
+* [Systemd](https://www.ibm.com/developerworks/cn/linux/1407_liuming_init3/index.html)
+* [system V与systemd](https://blog.csdn.net/qinhan728/article/details/48792691)
 ## man systemd
-systemd 是linux操作系统的系统和服务管理器，在boot启动后的第一个进程（PID=1），systemd扮演初始化系统，其启动和维护用户空间服务。
+systemd 是linux操作系统的系统和服务管理器，作为boot启动后的第一个进程（PID=1），systemd扮演初始化系统，以及启动和维护用户空间服务。
+为了兼容SysV，如果systemd初始化被调用并且进程id不是1，它将执行`telinit`，并且将同步参数到该应用，所以在正常系统登录状态下的init和telinit是等同的。更多信息通过`man telinit` 了解。
+当作为系统实例启动，systemd通过`system.conf` 解析配置文件，如果作为用户进程启动，从`user.conf`解析配置文件,更多信息通过`systemd-system.conf` 了解。
+## systemd vs sysv init
+* 系统同时存在sysV init脚本使能和systemd service，那么到底是生谁效的？
+    如果同时存在systemd 单元文件和sysVinit脚本，亦或者upstart配置文件，理论上systemd>sysv init>upstart.
+* 如下路径的unit 关系，哪些unit是使能的?
+    参考 `man systemctl `->`COMMANDS`->`Unit File Commands`-> `enable NAME...`
+    在`/lib/systemd/system` 保存了所有unit file，其中部分`.service` 文件包含`[install]` 部分，当调用`systemctl enable watchdog.service` 会在 `/etc/systemd/systemd`下面创建软连接。开机通过查找该路径下面的软连接启动对应服务。
+    ```bash
+    $ cat watchdog.service
+    [Install]
+    WantedBy=multi-user.target
+    ```
+    ```bash
+    $ tree /etc/systemd/system
+    /etc/systemd/system
+    ├── multi-user.target.wants
+    │   ├── watchdog.service -> /lib/systemd/system/watchdog.service
+    ```
+    可以通过`systemctl list-unit-files |grep enable `查找所有使能的unit文件，同时可以通过`systemctl preset-all `复位所有使能的unit file。
+* systemd如何控制sysV init脚本?
+    ```bash
+    /lib/systemd/system/supervisor.service
+    /etc/systemd/system/multi-user.target.wants/supervisor.service #软连接
+    ```
+    如果同时存在`supervisor.service` 和对应软连接，此时启动由systemd控制，并且状态为`enable`。
+    ```bash
+    $ systemctl list-unit-files |grep supervisor
+    supervisor.service                           enabled
+    ```
+    如果存在`superviosr.service`不存在对应的软连接，此时启动有systemd控制，状态为`disable`,开机不启动supervisor服务。
+    ```bash
+    $ systemctl list-unit-files |grep supervisor
+    supervisor.service                           disabled
+    ```
+    ```
+    /etc/init.d/supervisor
+    /etc/rc5.d/S01supervisor
+    ```
+    如果同时存在`supervisor`和`S01supervisor`  并且不存在如上的systemd 单元文件，那么此时启动由sysVinit控制。
+如上问题还是只有从`man systemctl` 当中找答案哦。
+## systemd command
+```bash
+systemctl (1)        - Control the systemd system and service manager
+systemd (1)          - systemd system and service manager
+systemd-activate (8) - Test socket activation of daemons
+systemd-analyze (1)  - Analyze system boot-up performance
+systemd-ask-password (1) - Query the user for a system password
+systemd-ask-password-console.path (8) - Query the user for system passwords on the console and via wall
+systemd-ask-password-console.service (8) - Query the user for system passwords on the console and via wall
+systemd-ask-password-wall.path (8) - Query the user for system passwords on the console and via wall
+systemd-ask-password-wall.service (8) - Query the user for system passwords on the console and via wall
+systemd-backlight (8) - Load and save the display backlight brightness at boot and shutdown
+systemd-backlight@.service (8) - Load and save the display backlight brightness at boot and shutdown
+systemd-binfmt (8)   - Configure additional binary formats for executables at boot
+systemd-binfmt.service (8) - Configure additional binary formats for executables at boot
+systemd-bootchart (1) - Boot performance graphing tool
+systemd-cat (1)      - Connect a pipeline or program's output with the journal
+systemd-cgls (1)     - Recursively show control group contents
+systemd-cgtop (1)    - Show top control groups by their resource usage
+systemd-cryptsetup (8) - Full disk decryption logic
+systemd-cryptsetup-generator (8) - Unit generator for /etc/crypttab
+systemd-cryptsetup@.service (8) - Full disk decryption logic
+systemd-debug-generator (8) - Generator for enabling a runtime debug shell and masking specific units at boot
+systemd-delta (1)    - Find overridden configuration files
+systemd-detect-virt (1) - Detect execution in a virtualized environment
+systemd-efi-boot-generator (8) - Generator for automatically mounting the EFI System Partition used by the current boot to /boot
+systemd-escape (1)   - Escape strings for usage in system unit names
+systemd-fsck (8)     - File system checker logic
+systemd-fsck-root.service (8) - File system checker logic
+systemd-fsck@.service (8) - File system checker logic
+systemd-fstab-generator (8) - Unit generator for /etc/fstab
+systemd-getty-generator (8) - Generator for enabling getty instances on the console
+systemd-gpt-auto-generator (8) - Generator for automatically discovering and mounting root, /home and /srv partitions, as well as discovering and enabling swap partitions, based on GPT par...
+systemd-halt.service (8) - System shutdown logic
+systemd-hibernate.service (8) - System sleep state logic
+systemd-hostnamed (8) - Host name bus mechanism
+systemd-hostnamed.service (8) - Host name bus mechanism
+systemd-hybrid-sleep.service (8) - System sleep state logic
+systemd-inhibit (1)  - Execute a program with an inhibition lock taken
+systemd-initctl (8)  - /dev/initctl compatibility
+systemd-initctl.service (8) - /dev/initctl compatibility
+systemd-initctl.socket (8) - /dev/initctl compatibility
+systemd-journald (8) - Journal service
+systemd-journald-dev-log.socket (8) - Journal service
+systemd-journald.service (8) - Journal service
+systemd-journald.socket (8) - Journal service
+systemd-kexec.service (8) - System shutdown logic
+systemd-localed (8)  - Locale bus mechanism
+systemd-localed.service (8) - Locale bus mechanism
+systemd-logind (8)   - Login manager
+systemd-logind.service (8) - Login manager
+systemd-machine-id-setup (1) - Initialize the machine ID in /etc/machine-id
+systemd-machined (8) - Virtual machine and container registration manager
+systemd-machined.service (8) - Virtual machine and container registration manager
+systemd-modules-load (8) - Configure kernel modules to load at boot
+systemd-modules-load.service (8) - Configure kernel modules to load at boot
+systemd-networkd (8) - Network manager
+systemd-networkd-wait-online (8) - Wait for network to come online
+systemd-networkd-wait-online.service (8) - Wait for network to come online
+systemd-networkd.service (8) - Network manager
+systemd-notify (1)   - Notify service manager about start-up completion and other daemon status changes
+systemd-nspawn (1)   - Spawn a namespace container for debugging, testing and building
+systemd-path (1)     - List and query system and user paths
+systemd-poweroff.service (8) - System shutdown logic
+systemd-quotacheck (8) - File system quota checker logic
+systemd-quotacheck.service (8) - File system quota checker logic
+systemd-random-seed (8) - Load and save the system random seed at boot and shutdown
+systemd-random-seed.service (8) - Load and save the system random seed at boot and shutdown
+systemd-readahead (8) - Disk read ahead logic
+systemd-readahead-collect.service (8) - Disk read ahead logic
+systemd-readahead-done.service (8) - Disk read ahead logic
+systemd-readahead-done.timer (8) - Disk read ahead logic
+systemd-readahead-replay.service (8) - Disk read ahead logic
+systemd-reboot.service (8) - System shutdown logic
+systemd-remount-fs (8) - Remount root and kernel file systems
+systemd-remount-fs.service (8) - Remount root and kernel file systems
+systemd-resolved (8) - Network Name Resolution manager
+systemd-resolved.service (8) - Network Name Resolution manager
+systemd-rfkill (8)   - Load and save the RF kill switch state at boot and shutdown
+systemd-rfkill@.service (8) - Load and save the RF kill switch state at boot and shutdown
+systemd-run (1)      - Run programs in transient scope or service units
+systemd-shutdown (8) - System shutdown logic
+systemd-shutdownd (8) - Scheduled shutdown service
+systemd-shutdownd.service (8) - Scheduled shutdown service
+systemd-shutdownd.socket (8) - Scheduled shutdown service
+systemd-sleep (8)    - System sleep state logic
+systemd-sleep.conf (5) - Suspend and hibernation configuration file
+systemd-socket-proxyd (8) - Bidirectionally proxy local sockets to another (possibly remote) socket.
+systemd-suspend.service (8) - System sleep state logic
+systemd-sysctl (8)   - Configure kernel parameters at boot
+systemd-sysctl.service (8) - Configure kernel parameters at boot
+systemd-system-update-generator (8) - Generator for redirecting boot to offline update mode
+systemd-system.conf (5) - System and session service manager configuration file
+systemd-sysusers (8) - Allocate system users and groups
+systemd-sysusers.service (8) - Allocate system users and groups
+systemd-timedated (8) - Time and date bus mechanism
+systemd-timedated.service (8) - Time and date bus mechanism
+systemd-timesyncd (8) - Network Time Synchronization
+systemd-timesyncd.service (8) - Network Time Synchronization
+systemd-tmpfiles (8) - Creates, deletes and cleans up volatile and temporary files and directories
+systemd-tmpfiles-clean.service (8) - Creates, deletes and cleans up volatile and temporary files and directories
+systemd-tmpfiles-clean.timer (8) - Creates, deletes and cleans up volatile and temporary files and directories
+systemd-tmpfiles-setup-dev.service (8) - Creates, deletes and cleans up volatile and temporary files and directories
+systemd-tmpfiles-setup.service (8) - Creates, deletes and cleans up volatile and temporary files and directories
+systemd-tty-ask-password-agent (1) - List or process pending systemd password requests
+systemd-udevd (8)    - Device event managing daemon
+systemd-udevd-control.socket (8) - Device event managing daemon
+systemd-udevd-kernel.socket (8) - Device event managing daemon
+systemd-udevd.service (8) - Device event managing daemon
+systemd-update-utmp (8) - Write audit and utmp updates at bootup, runlevel changes and shutdown
+systemd-update-utmp-runlevel.service (8) - Write audit and utmp updates at bootup, runlevel changes and shutdown
+systemd-update-utmp.service (8) - Write audit and utmp updates at bootup, runlevel changes and shutdown
+systemd-user-sessions (8) - Permit user logins after boot, prohibit user logins at shutdown
+systemd-user-sessions.service (8) - Permit user logins after boot, prohibit user logins at shutdown
+systemd-user.conf (5) - System and session service manager configuration file
+systemd.automount (5) - Automount unit configuration
+systemd.device (5)   - Device unit configuration
+systemd.directives (7) - Index of configuration directives
+systemd.exec (5)     - Execution environment configuration
+systemd.index (7)    - List all manpages from the systemd project
+systemd.journal-fields (7) - Special journal fields
+systemd.kill (5)     - Process killing procedure configuration
+systemd.link (5)     - Network device configuration
+systemd.mount (5)    - Mount unit configuration
+systemd.netdev (5)   - Virtual Network Device configuration
+systemd.network (5)  - Network configuration
+systemd.path (5)     - Path unit configuration
+systemd.preset (5)   - Service enablement presets
+systemd.resource-control (5) - Resource control unit settings
+systemd.scope (5)    - Scope unit configuration
+systemd.service (5)  - Service unit configuration
+systemd.slice (5)    - Slice unit configuration
+systemd.snapshot (5) - Snapshot unit configuration
+systemd.socket (5)   - Socket unit configuration
+systemd.special (7)  - Special systemd units
+systemd.swap (5)     - Swap unit configuration
+systemd.target (5)   - Target unit configuration
+systemd.time (7)     - Time and date specifications
+systemd.timer (5)    - Timer unit configuration
+systemd.unit (5)     - Unit configuration
+```
+## systemd source review
+* https://github.com/systemd/systemd
+* https://github.com/systemd/systemd/releases
-为了兼容SysV，如果systemd以初始化被调用并且进程id不是1，它将执行`telinit`
-当做为系统实例启动，systemd从`system.conf` 配置文件开始解释，否则从`user.conf`,更多信息参考`systemd-system.conf`。
 </markdown>

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