# Linux_RH124_10_服務管理 - 服務(service)本質就是進程，但是運行在後台的，通常都會監聽某個端口，等待其它程序的請求，如：mysql、sshd、防火墻…等。 - 傳統的Linux都是靠System V的init來啟動各項系統服務，而現行主流的Linux發行版都用systemd來管理系統服務，主要systemd有相依性檢查，會將有相關性的服務一并開啟，所以systemd管理下開機速度更快、效能更好。 - 所有被systemd管理的服務被稱為Service Unit - systemd的PID一定為1 ```bash [mickey@localhost system]$ ps -aux|grep systemd root 1 0.0 0.3 179248 13720 ? Ss 07:07 0:01 /usr/lib/systemd/systemd --switched-root --system --deserialize 18 ``` - 套件安裝時會在/lib/systemd/system中建立相應服務的文件 ```bash [mickey@localhost system]$ ll /lib/systemd/system | head -10 total 1516 -rw-r--r--. 1 root root 729 Jun 18 2019 accounts-daemon.service -rw-r--r--. 1 root root 502 May 27 2019 alsa-restore.service -rw-r--r--. 1 root root 465 May 27 2019 alsa-state.service -rw-r--r--. 1 root root 722 Nov 8 2018 anaconda-direct.service -rw-r--r--. 1 root root 240 Nov 8 2018 anaconda-nm-config.service -rw-r--r--. 1 root root 660 Nov 8 2018 anaconda-noshell.service -rw-r--r--. 1 root root 585 Nov 8 2018 anaconda-pre.service -rw-r--r--. 1 root root 442 Nov 8 2018 anaconda.service -rw-r--r--. 1 root root 532 Nov 8 2018 anaconda-shell@.service ``` 1. \*.service，通常為stay a long service(長駐服務) 2. \*.socket，臨時服務，如：systemd監聽port是否有異動，有則呼叫服務 3. \*.path，systemd監聽目錄是否有異動，有則呼叫服務 ## 🐧查看服務 systemctl 使用`systemctl`對systemd控制和操作，參考：[systemctl命令](https://wiki.archlinux.org/index.php/Systemd_(%E6%AD%A3%E9%AB%94%E4%B8%AD%E6%96%87)) ### 查看服務列表 - `systemctl list-units --type=<service|socket|path>`，查看所有指定副檔名的已啟動服務 `systemctl`，列出所有已啟動的服務 `list-units`，`systemctl`默認就是列出所有服務，可省略 `--type=<servic|socket|path>`，篩選指定副檔名 `--all`，啟動失敗的服務也一并列出 ```bash [mickey@localhost system]$ systemctl list-units --type=service|head -10 UNIT LOAD ACTIVE SUB DESCRIPTION accounts-daemon.service loaded active running Accounts Service alsa-state.service loaded active running Manage Sound Card State (restore and store) atd.service loaded active running Job spooling tools auditd.service loaded active running Security Auditing Service avahi-daemon.service loaded active running Avahi mDNS/DNS-SD Stack chronyd.service loaded active running NTP client/server colord.service loaded active running Manage, Install and Generate Color Profiles crond.service loaded active running Command Scheduler cups.service loaded active running CUPS Scheduler ``` 1. UNIT，service unit檔名 2. LOAD，是否被systemd讀進記憶體中 3. ACTIVE，服務正常啟動中 4. SUB，running-->正在執行，exited-->服務已結束 5. DESCRIPTION，服務描述 - `systemctl list-unit-files`，查看已安裝service unit ```bash [mickey@localhost system]$ systemctl list-unit-files --type=service|head -10 UNIT FILE STATE accounts-daemon.service enabled alsa-restore.service static alsa-state.service static anaconda-direct.service static anaconda-nm-config.service static anaconda-noshell.service static anaconda-pre.service static anaconda-shell@.service static debug-shell.service disabled ``` 1. UNIT FILE，service unit檔名 2. STATE，service unit狀態 1. enabled，電腦啟動時此服務會自動開啟 2. disabled，enabled相反 3. static，不會自動啟動，也無法手動啟動，通常為其他程式的相依服務 4. masked，沖突性服務，設定則無法開啟 ### 查看指定服務狀態 - `systemctl status <UNIT>`，查看指定服務狀態，.service可省略 1. vendor preset: enabled，表示工廠初始值 ```bash [mickey@localhost system]$ systemctl status sshd.service ● sshd.service - OpenSSH server daemon Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled) Active: active (running) since Thu 2021-03-25 07:07:21 EDT; 2h 45min ago Docs: man:sshd(8) man:sshd_config(5) Main PID: 1119 (sshd) Tasks: 1 (limit: 23977) Memory: 5.5M CGroup: /system.slice/sshd.service └─1119 /usr/sbin/sshd -D -oCiphers=aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes256-ctr,aes256-cbc,a> Mar 25 07:07:21 localhost.localdomain systemd[1]: Starting OpenSSH server daemon... Mar 25 07:07:21 localhost.localdomain sshd[1119]: Server listening on 0.0.0.0 port 22. Mar 25 07:07:21 localhost.localdomain sshd[1119]: Server listening on :: port 22. Mar 25 07:07:21 localhost.localdomain systemd[1]: Started OpenSSH server daemon. Mar 25 07:08:55 localhost.localdomain sshd[2361]: Accepted password for mickey from 192.168.56.1 port 2445 ssh2 Mar 25 07:08:55 localhost.localdomain sshd[2361]: pam_unix(sshd:session): session opened for user mickey by (uid=0) ``` - `systemctl is-active <UNIT>`，查看指定服務是否被啟動，.service可省略 ```bash [mickey@localhost system]$ systemctl is-active sshd.service active ``` - `systemctl is-enabled <UNIT>`，查看指定服務開機是否會自動啟動，.service可省略 ```bash [mickey@localhost system]$ systemctl is-enabled sshd.service enabled ``` - `systemctl is-failed <UNIT>`，查看指定服務啟動是否夫敗，.service可省略 ```bash [mickey@localhost system]$ systemctl is-failed sshd.service active ``` ### 重新載入systemd - `systemctl daemon-reload`，重新載入systemd ```bash [mickey@localhost system]$ systemctl daemon-reload ==== AUTHENTICATING FOR org.freedesktop.systemd1.reload-daemon ==== Authentication is required to reload the systemd state. Authenticating as: mickey ``` ## 🐧操作服務 systemctl ### 基本操作 `systemctl <start|stop|restart|reload> <UNIT>`，.service可省略 - start，啟動 - stop，關閉 ```bash [mickey@localhost system]$ systemctl stop sshd.service ==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-units ==== Authentication is required to stop 'sshd.service'. Authenticating as: mickey ``` - restart，重啟 - reload，重新載入配置 - mask，禁用，實際上是將服務建立soft link至/dev/null ```bash [mickey@localhost system]$ systemctl mask sendmail.service Unit sendmail.service does not exist, proceeding anyway. ==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-unit-files ==== Authentication is required to manage system service or unit files. Authenticating as: mickey Password: ==== AUTHENTICATION COMPLETE ==== Created symlink /etc/systemd/system/sendmail.service → /dev/null. ==== AUTHENTICATING FOR org.freedesktop.systemd1.reload-daemon ==== Authentication is required to reload the systemd state. Authenticating as: mickey Password: ==== AUTHENTICATION COMPLETE ==== [mickey@localhost system]$ systemctl status sendmail ● sendmail.service Loaded: masked (Reason: Unit sendmail.service is masked.) Active: inactive (dead) ``` - unmask，取消禁用，實際上是刪除soft link ```bash [mickey@localhost system]$ systemctl unmask sendmail ==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-unit-files ==== Authentication is required to manage system service or unit files. Authenticating as: mickey Password: ==== AUTHENTICATION COMPLETE ==== Removed /etc/systemd/system/sendmail.service. ==== AUTHENTICATING FOR org.freedesktop.systemd1.reload-daemon ==== Authentication is required to reload the systemd state. Authenticating as: mickey Password: ==== AUTHENTICATION COMPLETE ==== ``` ### 搜索相依服務 `systemctl list-dependencies <UNIT>`，.service可省略 ```bash [mickey@localhost system]$ systemctl list-dependencies sshd.service sshd.service ● ├─system.slice ● ├─sshd-keygen.target ● │ ├─sshd-keygen@ecdsa.service ● │ ├─sshd-keygen@ed25519.service ● │ └─sshd-keygen@rsa.service ● └─sysinit.target ● ├─dev-hugepages.mount ``` ### 開機啟用/關閉服務 - `systemctl enable <UNIT>`，設置開機啟動服務 當服務開機啟用設置enable時，系統會將/etc/systemd/system/服務名 建立soft link至/userr/lib/systemd/system/服務名 ```bash [mickey@localhost system]$ systemctl enable sshd.service ==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-unit-files ==== Authentication is required to manage system service or unit files. Authenticating as: mickey Password: ==== AUTHENTICATION COMPLETE ==== Created symlink /etc/systemd/system/multi-user.target.wants/sshd.service → /usr/lib/systemd/system/sshd.service. ==== AUTHENTICATING FOR org.freedesktop.systemd1.reload-daemon ==== Authentication is required to reload the systemd state. Authenticating as: mickey Password: ==== AUTHENTICATION COMPLETE ==== ``` - `systemctl disable <UNIT>`，設置開機不啟動服務，.service可省略 實際上是將soft link刪除 ```bash [mickey@localhost system]$ systemctl disable sshd.service ==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-unit-files ==== Authentication is required to manage system service or unit files. Authenticating as: mickey Password: ==== AUTHENTICATION COMPLETE ==== Removed /etc/systemd/system/multi-user.target.wants/sshd.service. ==== AUTHENTICATING FOR org.freedesktop.systemd1.reload-daemon ==== Authentication is required to reload the systemd state. Authenticating as: mickey Password: ==== AUTHENTICATION COMPLETE ==== ``` # 其他 ## telnet-windows使用 在windows cmd中可使用`telnet`檢查linux的某個端口是否在監聽 參考：[telnet 不是内部或外部命令怎么辦呢?](https://goodlucky.pixnet.net/blog/post/48400569-%5bwin10%5d-telnet-%e4%b8%8d%e6%98%af%e5%86%85%e9%83%a8%e6%88%96%e5%a4%96%e9%83%a8%e5%91%bd%e4%bb%a4%e6%80%8e%e4%b9%88%e8%be%a6%e5%91%a2%3f) ```bash telnet 192.168.0.14 22 ``` ## setup `setup`，查看服務名 ![Linux_RH124_10_服務管理_02_setup](https://github.com/MickeyHuang233/CodingStudyNote/blob/main/03_Linux/%F0%9F%90%A7RH124/images/Linux_RH124_10_%E6%9C%8D%E5%8B%99%E7%AE%A1%E7%90%86_02_setup.png?raw=true)