--restart=always參數能夠使我們在重啓docker時，自動啓動相關容器。
Docker容器的重啓策略如下：
no，默認策略，在容器退出時不重啓容器
on-failure，在容器非正常退出時（退出狀態非0），纔會重啓容器
on-failure:3，在容器非正常退出時重啓容器，最多重啓3次
always，在容器退出時總是重啓容器
unless-stopped，在容器退出時總是重啓容器，但是不考慮在Docker守護進程啓動時就已經停止了的容器
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版權聲明：本文爲CSDN博主「易生一世」的原創文章，遵循CC 4.0 BY 版權協議，轉載請附上原文出處鏈接及本聲明。
原文鏈接：https://blog.csdn.net/taiyangdao/article/details/73076019
首先我們先看下正常啓動容器不加參數的情況重啓docker會出現什麼情況
一、啓動時候添加參數
1、不加–restart=always參數啓動容器
[root@localhost /]# docker run -d tomcat
1a7a3b5112fd310dc70903df479203a81d7d64f7c19ea0aca8fff8ece10e04a4
[root@localhost /]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1a7a3b5112fd tomcat "catalina.sh run" 29 seconds ago Up 28 seconds 8080/tcp friendly_clarke
[root@localhost /]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1a7a3b5112fd tomcat "catalina.sh run" 32 seconds ago Up 31 seconds 8080/tcp friendly_clarke
2、重啓docker，查看狀態，可以看到，重啓docker之後，容器也停止了運行，這在生產環境上是非常危險的。
[root@localhost /]# systemctl restart docker
[root@localhost /]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
[root@localhost /]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1a7a3b5112fd tomcat "catalina.sh run" About a minute ago Exited (143) 5 seconds ago friendly_clarke
[root@localhost /]#
3、下面我們使用-restart=always參數啓動容器
[root@localhost /]# docker run -d --restart always tomcat
c5557254c6d90b1ba8f9a93ff66e6a28f172e92a56cf945af533327f38152fbc
[root@localhost /]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c5557254c6d9 tomcat "catalina.sh run" 4 seconds ago Up 3 seconds 8080/tcp fervent_goldstine
[root@localhost /]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c5557254c6d9 tomcat "catalina.sh run" 8 seconds ago Up 7 seconds 8080/tcp fervent_goldstine
1a7a3b5112fd tomcat "catalina.sh run" 2 minutes ago Exited (143) About a minute ago friendly_clarke
[root@localhost /]# systemctl restart docker
[root@localhost /]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c5557254c6d9 tomcat "catalina.sh run" 18 seconds ago Up 3 seconds 8080/tcp fervent_goldstine
[root@localhost /]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c5557254c6d9 tomcat "catalina.sh run" 26 seconds ago Up 10 seconds 8080/tcp fervent_goldstine
1a7a3b5112fd tomcat "catalina.sh run" 3 minutes ago Exited (143) About a minute ago friendly_clarke
[root@localhost /]#
二、命令修改
在啓動時如果沒有添加這個參數怎麼辦呢，比如1a7a3b5112fd這個容器在啓動的時候是沒有添加–restart=always參數的，針對這種情況我們可以使用命令進行修改。docker container update --restart=always 容器名字
[root@localhost /]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c5557254c6d9 tomcat "catalina.sh run" 26 seconds ago Up 10 seconds 8080/tcp fervent_goldstine
1a7a3b5112fd tomcat "catalina.sh run" 3 minutes ago Exited (143) About a minute ago friendly_clarke
[root@localhost /]# docker container update --restart=always 1a7a3b5112fd
1a7a3b5112fd
[root@localhost /]# systemctl restart docker
[root@localhost /]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c5557254c6d9 tomcat "catalina.sh run" 7 minutes ago Up 3 seconds 8080/tcp fervent_goldstine
1a7a3b5112fd tomcat "catalina.sh run" 9 minutes ago Up 3 seconds 8080/tcp friendly_clarke
[root@localhost /]#
三、修改配置文件
除了上面兩種方式之後還可以通過修改容器的配置文件來修儘管這個參數，首先停止容器，不然無法修改配置文件
配置默認文件路徑爲：/var/lib/docker/containers/容器ID
在該目錄下找到一個文件 hostconfig.json ，找到該文件中關鍵字 RestartPolicy
修改前配置：“RestartPolicy”:{“Name”:“no”,“MaximumRetryCount”:0}
修改後配置：“RestartPolicy”:{“Name”:“always”,“MaximumRetryCount”:0}
最後啓動容器。
[root@localhost /]# docker container update --restart=no 1a7a3b5112fd
1a7a3b5112fd
[root@localhost /]# systemctl restart docker
[root@localhost /]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c5557254c6d9 tomcat "catalina.sh run" 11 minutes ago Up 2 seconds 8080/tcp fervent_goldstine
1a7a3b5112fd tomcat "catalina.sh run" 14 minutes ago Exited (143) 3 seconds ago friendly_clarke
[root@localhost ~]# cd /docker/containers/1a7a3b5112fd310dc70903df479203a81d7d64f7c19ea0aca8fff8ece10e04a4/
[root@localhost 1a7a3b5112fd310dc70903df479203a81d7d64f7c19ea0aca8fff8ece10e04a4]# ls
1a7a3b5112fd310dc70903df479203a81d7d64f7c19ea0aca8fff8ece10e04a4-json.log config.v2.json hostname mounts resolv.conf.hash
checkpoints hostconfig.json hosts resolv.conf
[root@localhost 1a7a3b5112fd310dc70903df479203a81d7d64f7c19ea0aca8fff8ece10e04a4]# more hostconfig.json
{"Binds":null,"ContainerIDFile":"","LogConfig":{"Type":"json-file","Config":{}},"NetworkMode":"default","PortBindings":{},"RestartPolicy":{"Name":"no","MaximumR
etryCount":0},"AutoRemove":false,"VolumeDriver":"","VolumesFrom":null,"CapAdd":null,"CapDrop":null,"Capabilities":null,"Dns":[],"DnsOptions":[],"DnsSearch":[],"Extr
aHosts":null,"GroupAdd":null,"IpcMode":"private","Cgroup":"","Links":null,"OomScoreAdj":0,"PidMode":"","Privileged":false,"PublishAllPorts":false,"ReadonlyRootfs":f
alse,"SecurityOpt":null,"UTSMode":"","UsernsMode":"","ShmSize":67108864,"Runtime":"runc","ConsoleSize":[0,0],"Isolation":"","CpuShares":0,"Memory":0,"NanoCpus":0,"C
groupParent":"","BlkioWeight":0,"BlkioWeightDevice":[],"BlkioDeviceReadBps":null,"BlkioDeviceWriteBps":null,"BlkioDeviceReadIOps":null,"BlkioDeviceWriteIOps":null,"
CpuPeriod":0,"CpuQuota":0,"CpuRealtimePeriod":0,"CpuRealtimeRuntime":0,"CpusetCpus":"","CpusetMems":"","Devices":[],"DeviceCgroupRules":null,"DeviceRequests":null,"
KernelMemory":0,"KernelMemoryTCP":0,"MemoryReservation":0,"MemorySwap":0,"MemorySwappiness":null,"OomKillDisable":false,"PidsLimit":null,"Ulimits":null,"CpuCount":0
,"CpuPercent":0,"IOMaximumIOps":0,"IOMaximumBandwidth":0,"MaskedPaths":["/proc/asound","/proc/acpi","/proc/kcore","/proc/keys","/proc/latency_stats","/proc/timer_li
st","/proc/timer_stats","/proc/sched_debug","/proc/scsi","/sys/firmware"],"ReadonlyPaths":["/proc/bus","/proc/fs","/proc/irq","/proc/sys","/proc/sysrq-trigger"]}
[root@localhost 1a7a3b5112fd310dc70903df479203a81d7d64f7c19ea0aca8fff8ece10e04a4]# sed -i 's/"RestartPolicy":{"Name":"no"/"RestartPolicy":{"Name":"always"/g' hostconfig.json
[root@localhost 1a7a3b5112fd310dc70903df479203a81d7d64f7c19ea0aca8fff8ece10e04a4]# more hostconfig.json
{"Binds":null,"ContainerIDFile":"","LogConfig":{"Type":"json-file","Config":{}},"NetworkMode":"default","PortBindings":{},"RestartPolicy":{"Name":"always","MaximumR
etryCount":0},"AutoRemove":false,"VolumeDriver":"","VolumesFrom":null,"CapAdd":null,"CapDrop":null,"Capabilities":null,"Dns":[],"DnsOptions":[],"DnsSearch":[],"Extr
aHosts":null,"GroupAdd":null,"IpcMode":"private","Cgroup":"","Links":null,"OomScoreAdj":0,"PidMode":"","Privileged":false,"PublishAllPorts":false,"ReadonlyRootfs":f
alse,"SecurityOpt":null,"UTSMode":"","UsernsMode":"","ShmSize":67108864,"Runtime":"runc","ConsoleSize":[0,0],"Isolation":"","CpuShares":0,"Memory":0,"NanoCpus":0,"C
groupParent":"","BlkioWeight":0,"BlkioWeightDevice":[],"BlkioDeviceReadBps":null,"BlkioDeviceWriteBps":null,"BlkioDeviceReadIOps":null,"BlkioDeviceWriteIOps":null,"
CpuPeriod":0,"CpuQuota":0,"CpuRealtimePeriod":0,"CpuRealtimeRuntime":0,"CpusetCpus":"","CpusetMems":"","Devices":[],"DeviceCgroupRules":null,"DeviceRequests":null,"
KernelMemory":0,"KernelMemoryTCP":0,"MemoryReservation":0,"MemorySwap":0,"MemorySwappiness":null,"OomKillDisable":false,"PidsLimit":null,"Ulimits":null,"CpuCount":0
,"CpuPercent":0,"IOMaximumIOps":0,"IOMaximumBandwidth":0,"MaskedPaths":["/proc/asound","/proc/acpi","/proc/kcore","/proc/keys","/proc/latency_stats","/proc/timer_li
st","/proc/timer_stats","/proc/sched_debug","/proc/scsi","/sys/firmware"],"ReadonlyPaths":["/proc/bus","/proc/fs","/proc/irq","/proc/sys","/proc/sysrq-trigger"]}
[root@localhost /]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c5557254c6d9 tomcat "catalina.sh run" 14 minutes ago Up 2 seconds 8080/tcp fervent_goldstine
1a7a3b5112fd tomcat "catalina.sh run" 17 minutes ago Up 2 seconds 8080/tcp friendly_clarke