技術標籤：開發系統相關

01.檢查systemd是否正在執行。

# ps -eaf | grep [s]ystemd
root         1     0  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd --switched-root --system --deserialize 23
root       444     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-journald
root       469     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-udevd
root       555     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-logind
dbus       556     1  0 16:27 ?        00:00:00 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
 

注意：systemd作為父守護程序執行（PID = 1）。 在上面的命令ps中使用（-e）選擇所有程序，（ - a）選擇除會話前導之外的所有程序和（-f）選擇完整格式列表（即-eaf）。

02.列出所有可用的單位

# systemctl list-unit-files
UNIT FILE                                   STATE   
proc-sys-fs-binfmt_misc.automount           static  
dev-hugepages.mount                         static  
dev-mqueue.mount                            static  
proc-sys-fs-binfmt_misc.mount               static  
sys-fs-fuse-connections.mount               static  
sys-kernel-config.mount                     static  
sys-kernel-debug.mount                      static  
tmp.mount                                   disabled
brandbot.path                               disabled
.....
 

03、檢查單元(cron.service)是否啟用?

# systemctl is-enabled crond.service
enabled

04.檢查單元或服務是否正在執行？

 systemctl status firewalld.service
firewalld.service - firewalld - dynamic firewall daemon
Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
Active: active (running) since Tue 2018-04-28 16:27:55 IST; 34min ago
Main PID: 549 (firewalld)
CGroup: /system.slice/firewalld.service
└─549 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid
Apr 28 16:27:51 tecmint systemd[1]: Starting firewalld - dynamic firewall daemon...
Apr 28 16:27:55 tecmint systemd[1]: Started firewalld - dynamic firewall daemon.
 

05.列出所有服務（包括啟用和禁用）

# systemctl list-unit-files --type=service
UNIT FILE                                   STATE   
arp-ethers.service                          disabled
auditd.service                              enabled 
[email protected]                             disabled
blk-availability.service                    disabled
brandbot.service                            static  
collectd.service                            disabled
console-getty.service                       disabled
console-shell.service                       disabled
cpupower.service                            disabled
crond.service                               enabled 
dbus-org.fedoraproject.FirewallD1.service   enabled 

06.如何在Linux中啟動，重新啟動，停止，重新載入和檢查服務（httpd.service）的狀態

# systemctl start httpd.service
# systemctl restart httpd.service
# systemctl stop httpd.service
# systemctl reload httpd.service
# systemctl status httpd.service
httpd.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
Active: active (running) since Tue 2018-04-28 17:21:30 IST; 6s ago
Process: 2876 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)
Main PID: 2881 (httpd)
Status: "Processing requests..."
CGroup: /system.slice/httpd.service
├─2881 /usr/sbin/httpd -DFOREGROUND
├─2884 /usr/sbin/httpd -DFOREGROUND
├─2885 /usr/sbin/httpd -DFOREGROUND
├─2886 /usr/sbin/httpd -DFOREGROUND
├─2887 /usr/sbin/httpd -DFOREGROUND
└─2888 /usr/sbin/httpd -DFOREGROUND
Apr 28 17:21:30 tecmint systemd[1]: Starting The Apache HTTP Server...
Apr 28 17:21:30 tecmint httpd[2881]: AH00558: httpd: Could not reliably determine the server's fully q...ssage
Apr 28 17:21:30 tecmint systemd[1]: Started The Apache HTTP Server.
Hint: Some lines were ellipsized, use -l to show in full.

注意：當我們使用systemctl等啟動，重啟，停止和過載等命令時，我們將不會在終端上獲得任何輸出，只有status命令會列印輸出。

07.如何在引導時啟用服務並啟用或禁用服務（系統引導時自動啟動服務）

# systemctl is-active httpd.service
# systemctl enable httpd.service
# systemctl disable httpd.service

實戰

建立一個systemd服務

cd/etc/systemd/system

sudo nano ss2.service

ss2.service內容如下

[Unit]
Description=ss2 service
After=network.target
[Service]
Type=simple
ExecStart=/bin/bash /home/hl/sh/ss2.sh

[Install]
WantedBy=multi-user.target

systemctl enable ss2

systemctl start ss2