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/ etc/inittab file field and its description is what, I believe that many inexperienced people do not know what to do, so this paper summarizes the causes of the problem and solutions, through this article I hope you can solve this problem.

Each entry in the / etc/inittab file has the same structure, divided into four fields separated by a colon ":". The details are as follows:

Identifier: run_level: action: process

Among them, each field and its related description are as follows:

Identifier entry identifier, up to 4 characters. Used to uniquely identify each entry in the / etc/inittab file

The run_level system runlevel, that is, the init level at which the entry is executed. Used to specify which runtime level the corresponding entry applies to, that is, in which runlevel it is processed. If the field is empty, the corresponding entry will apply to all runlevels. In this field, you can specify one or more runlevels at the same time, each of which is represented by the number 0.1.2.3.4.5.6 or the letters a, b, c, respectively, and does not need to be separated.

Action action keyword. Lets you specify the action that the init (M) command or process takes on the corresponding process (defined in the process field). Specific actions include:

1. Boot: the process is executed only during the boot process, but does not wait for the process to finish; when the process dies, the process is not restarted.

2. Bootwait: execute the process only during the boot process and wait for the process to end: when the process dies, the process is not restarted. In fact, these entries are processed only after the system is booted and enter multi-user mode from single-user mode; if the default runlevel of the system is set to 2 (that is, multi-user mode), then these entries will be processed immediately after the system boots.

3. Initdefault: specify the default run level of the system. When the system starts, init will first look for the entry. If there is an init, it will determine which runlevel the system will initially enter. Specifically, init specifies that the maximum number in the entry "run_level" field (that is, the highest runlevel) is the default runlevel for the current system; if the field is empty, it is interpreted as "0123456" with "6" as the default runlevel. If the entry does not exist, init will require the user to specify an initial runtime at system startup.

4. Off: if the corresponding process is running, issue a warning signal, wait 20 seconds, and then forcibly terminate the process with the kill signal. If the corresponding process does not exist, the entry is ignored.

5. Once: start the appropriate process, but continue to process the next entry in the / etc/inittab file without waiting for the process to finish; when the process dies, init does not restart the process. Note: when moving from one runlevel to another, init does not restart the process if the corresponding process is still running.

6. Ondemand: the function is exactly the same as "respawn", but it is only used for registrations with runtime level a, b, or c.

7. Powerfail: execute the corresponding process only when the init receives a power failure signal, but do not wait for the process to end.

8. Powerwait: execute the corresponding process only when the init receives a power failure signal, and wait for the process to finish before continuing any processing on the / etc/inittab file.

9. Respawn: if the corresponding process does not already exist, init starts the process and continues to scan the / etc/inittab file without waiting for the end of the process; when the process dies, init will restart the process. If the corresponding process already exists, init ignores the entry and continues to scan the / etc/inittab file.

10. Sysinit: init executes these entries only when you start or restart the system and enter a single user first. Init does not execute these entries when the system enters single-user mode from run-level 1mur6. Entries with the "action" field of "sysinit" do not specify any runtime in the "run_level" field.

11. Wait: start the process and wait for it to finish before processing the next entry in the / etc/inittab file.

The shell command to be executed by process. Any legal shell syntax applies to this field.

After reading the above, have you mastered the fields and descriptions of the / etc/inittab file? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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