Redis 错误：Failed with result 'start-limit-hit'
背景
Redis 版本为 5.0.4；
文件 /etc/systemd/system/redis.service 内容如下：
[Unit]
Description=Redis Datastore Server
After=network.target
[Service]
Type=forking
PIDFile=/var/run/redis/redis_6379
User=redis
Group=redis
Environment=statedir=/var/run/redis
PermissionsStartOnly=true
ExecStartPre=/bin/mkdir -p ${statedir}
ExecStartPre=/bin/chown -R redis:redis ${statedir}
ExecStart=/usr/local/bin/redis-server /etc/redis/redis.conf --supervised systemd
ExecReload=/bin/kill -USR2 $MAINPID
ExecStop=/usr/local/bin/redis-cli shutdown
Restart=always
[Install]
WantedBy=multi-user.target
运行
在使用 systemctl 启动 Redis 时报错：
sudo systemctl daemon-reload
sudo systemctl start redis
错误日志：
Job for redis-server.service failed because the control process exited with error code. See "systemctl status redis-server.service" and "journalctl -xe" for details.
根据提示用命令 systemctl status redis-server.service 查看结果如下：
● redis-server.service - Redis Datastore Server
Loaded: loaded (/lib/systemd/system/redis-server.service; enabled; vendor preset: enabled)
Active: failed (Result: start-limit-hit) since Thu 2019-04-18 15:36:10 CST; 5s ago
Process: 8341 ExecStart=/usr/bin/redis-server /etc/redis/redis.conf --supervised systemd (code=exited
Process: 8337 ExecStartPre=/bin/chown -R redis:redis ${statedir} (code=exited, status=0/SUCCESS)
Process: 8333 ExecStartPre=/bin/mkdir -p ${statedir} (code=exited, status=0/SUCCESS)
Apr 18 15:36:10 dl26 systemd[1]: Failed to start Redis Datastore Server.
Apr 18 15:36:10 dl26 systemd[1]: redis-server.service: Unit entered failed state.
Apr 18 15:36:10 dl26 systemd[1]: redis-server.service: Failed with result 'exit-code'.
Apr 18 15:36:10 dl26 systemd[1]: redis-server.service: Service hold-off time over, scheduling restart.
Apr 18 15:36:10 dl26 systemd[1]: Stopped Redis Datastore Server.
Apr 18 15:36:10 dl26 systemd[1]: redis-server.service: Start request repeated too quickly.
Apr 18 15:36:10 dl26 systemd[1]: Failed to start Redis Datastore Server.
Apr 18 15:36:10 dl26 systemd[1]: redis-server.service: Unit entered failed state.
Apr 18 15:36:10 dl26 systemd[1]: redis-server.service: Failed with result 'start-limit-hit'.
发现 ExecStart=/usr/bin/redis-server /etc/redis/redis.conf --supervised systemd 报错，执行该命令出现如下错误日志：
*** FATAL CONFIG FILE ERROR ***
Reading the configuration file, at line 88
>>> 'protected-mode yes'
Bad directive or wrong number of arguments
问题是在处理配置文件时出现参数不匹配现象，原因是因为我在用源码安装 redis 后还用 apt-get install redis 的方法安装了一个旧版本的 redis，在 /usr/bin/ 目录下的 redis-server 不是最新版本，故出现不兼容的问题。
解决方法：
cp -r redis/src/redis-server /usr/bin/redis-server
再次执行：
sudo systemctl daemon-reload
sudo systemctl start redis
仍然报同样的错误，执行/usr/bin/redis-server /etc/redis/redis.conf --supervised systemd，日志如下：
8436:C 18 Apr 2019 15:37:50.558 # Can't chdir to '/home/chenxiang/redis': No such file or directory
发现是目录名称不存在，文件 /etc/redis/redis.conf 中的目录名称为 /home/chenxiang/redis，而实际 redis 目录名称为 /home/chenxiang/redis-5.0.4，修改实际目录名称为 redis 即解决这一问题。
继续运行：
sudo systemctl daemon-reload
sudo systemctl start redis
出现了新的错误：
Job for redis-server.service failed because a timeout was exceeded. See "systemctl status redis-server.service" and "journalctl -xe" for details.
通过 systemctl status redis-server.service 查看日志信息：
● redis-server.service - Redis Datastore Server
Loaded: loaded (/lib/systemd/system/redis-server.service; enabled; vendor preset: enabled)
Active: activating (start) since Thu 2019-04-18 15:49:48 CST; 1min 21s ago
Process: 8533 ExecStart=/usr/bin/redis-server /etc/redis/redis.conf --supervised systemd (code=exited
Process: 8530 ExecStartPre=/bin/chown -R redis:redis ${statedir} (code=exited, status=0/SUCCESS)
Process: 8527 ExecStartPre=/bin/mkdir -p ${statedir} (code=exited, status=0/SUCCESS)
CGroup: /system.slice/redis-server.service
└─8535 /usr/bin/redis-server 127.0.0.1:6379
Apr 18 15:49:48 dl26 systemd[1]: Starting Redis Datastore Server...
Apr 18 15:49:48 dl26 redis-server[8533]: 8533:C 18 Apr 2019 15:49:48.250 # oO0OoO0OoO0Oo Redis is start
Apr 18 15:49:48 dl26 redis-server[8533]: 8533:C 18 Apr 2019 15:49:48.250 # Redis version=5.0.4, bits=64
Apr 18 15:49:48 dl26 redis-server[8533]: 8533:C 18 Apr 2019 15:49:48.250 # Configuration loaded
Apr 18 15:49:48 dl26 redis-server[8533]: 8533:C 18 Apr 2019 15:49:48.250 # systemd supervision requeste
Apr 18 15:49:48 dl26 systemd[1]: redis-server.service: PID file /var/run/redis/redis_6379 not readable
发现 redis-server.service 没有足够的权限访问 /var/run/redis/redis_6379，需要修改/etc/systemd/system/redis.service为：
[Unit]
Description=Redis Datastore Server
After=network.target
[Service]
Type=forking
PIDFile=/var/run/redis/redis.pid
User=redis
Group=redis
Environment=statedir=/var/run/redis
PermissionsStartOnly=true
ExecStartPre=/bin/mkdir -p ${statedir}
ExecStartPre=/bin/chown -R redis:redis ${statedir}
ExecStartPost=/bin/sh -c "echo 6739 > /var/run/redis/redis.pid"
ExecStart=/usr/local/bin/redis-server /etc/redis/redis.conf --supervised systemd
ExecReload=/bin/kill -USR2 $MAINPID
ExecStop=/usr/local/bin/redis-cli shutdown
Restart=always
[Install]
WantedBy=multi-user.target
其中修改两行：PIDFile=/var/run/redis/redis.pid，以及 ExecStartPost=/bin/sh -c "echo 6739 > /var/run/redis/redis.pid"。
2019.4