Debian系统Docker无法通过systemctl启动故障求助

看起来你的docker.service配置文件被损坏了——它现在只有环境变量行，缺少了systemd服务必需的[Service]段和核心启动指令，这就是为什么systemctl报错说缺少ExecStart=和ExecStop=设置的原因。下面是具体的修复步骤：

步骤1：备份当前损坏的配置文件 #

先把现在的文件存个备份，避免后续操作出问题没法恢复：

sudo cp /lib/systemd/system/docker.service /lib/systemd/system/docker.service.bak

步骤2：重新生成正确的docker.service配置 #

对于Debian 9上的Docker 19.03版本，正确的docker.service应该包含完整的服务定义。你可以用下面的内容覆盖当前文件：

[Unit]
Description=Docker Application Container Engine
Documentation=https://docs.docker.com
BindsTo=containerd.service
After=network-online.target firewalld.service containerd.service
Wants=network-online.target
Requires=docker.socket

[Service]
Type=notify
# the default is not to use systemd for cgroups because the delegate issues still
# exists and systemd currently does not support the cgroup feature set required
# for containers run by docker
ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
ExecReload=/bin/kill -s HUP $MAINPID
TimeoutSec=0
RestartSec=2
Restart=always

# Note that StartLimit* options were moved from "Service" to "Unit" in systemd 229.
# Both the old, and new location are accepted by systemd 229 and up, so using the old location
# to make them work for either version of systemd.
StartLimitBurst=3

# Note that StartLimitInterval was renamed to StartLimitIntervalSec in systemd 230.
# Both the old, and new name are accepted by systemd 230 and up, so using the old name to make
# this option work for either version of systemd.
StartLimitInterval=60s

# Having non-zero Limit*s causes performance problems due to accounting overhead
# in the kernel. We recommend using cgroups to do container-local accounting.
LimitNOFILE=infinity
LimitNPROC=infinity
LimitCORE=infinity

# Comment TasksMax if your systemd version does not support it.
# Only systemd 226 and above support this option.
TasksMax=infinity

# set delegate yes so that systemd does not reset the cgroups of docker containers
Delegate=yes

# kill only the docker process, not all processes in the cgroup
KillMode=process

# restart the docker process if it exits prematurely
Restart=on-failure
StartLimitBurst=3
StartLimitInterval=60s

# 添加你原来的环境变量
Environment="GOOGLE_APPLICATION_CREDENTIALS=/etc/docker/key.json"

[Install]
WantedBy=multi-user.target

执行命令编辑文件并粘贴内容：

sudo nano /lib/systemd/system/docker.service
# 粘贴上述内容后，按Ctrl+O保存，回车确认，再按Ctrl+X退出编辑器

步骤3：重新加载systemd配置并启动Docker #

# 重新加载systemd的配置文件，让新的service生效
sudo systemctl daemon-reload
# 启动Docker服务
sudo systemctl start docker
# （可选）设置Docker开机自动启动
sudo systemctl enable docker

步骤4：验证服务状态 #

执行下面的命令确认Docker已经正常运行：

systemctl status docker

如果输出显示active (running)，就说明问题已经解决了。

补充说明 #

大概率是VM内存耗尽崩溃时，docker.service文件被异常损坏——系统突然断电/崩溃可能导致文件内容丢失或被篡改。现在我们恢复了完整的服务配置框架，同时保留了你需要的环境变量，systemd就能正确识别并管理Docker服务了。

内容的提问来源于stack exchange，提问作者DarkLeafyGreen