Detailed explanation of two ways of Linux service management: service and systemctl

1.service command

The service command actually goes to the /etc/init.d directory to execute related programs

# The service command starts the redis script service redis start
# Start the redis script directly /etc/init.d/redis start
# Startup update-rc.d redis defaults

We need to write the script ourselves

2.systemctl command

systemd is the latest initialization system (init) of the Linux system. Its function is to increase the system startup speed, start as few processes as possible, and start as many processes concurrently as possible.

The process management command corresponding to systemd is systemctl

1) The systemctl command is compatible with service

That is, systemctl will also go to the /etc/init.d directory to view and execute related programs

systemctl redis start
systemctl redis stop
# Systemctl enable redis

2) The systemctl command manages systemd's resource units

The systemd unit is placed in the directory / usr/lib/systemd/system(Centos)或/etc/systemd/system(Ubuntu)

There are four main types of files: mount, service, target, and want.

.mount File

The .mount file defines a mount point. The configuration of the What, Where, and Type data items in the [Mount] node is equivalent to the following command:

mount -t hugetlbfs /dev/hugepages hugetlbfs

.service file

The .service file defines a service, which is divided into three sections: [Unit], [Service], and [Install]

[Unit]

Description:

After: Start after network.target, auditd.service is started

ConditionPathExists: Execution conditions

[Service]

EnvironmentFile: The file where the variable is located

ExecStart: Execute the startup script

Restart: Restart when fail

[Install]
Alias: Service alias
WangtedBy: Required in multi-user mode

.target file

.target defines some basic components for .service files to call

.wants File

The .wants file defines the set of files to be executed. Each time it is executed, the files in the .wants folder will be executed.

Summarize

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