How to configure Linux Security Service Management

An important aspect of any computer security measure is to maintain the operation of the actual Control service. This article shows you how to configure Security Service management on a PC on a Linux operating system.

An important aspect of any computer security measure is to maintain the operation of the actual Control service, and to allow unnecessary network services to accept requests will increase the security risk of the system. Even though these network services are necessary for some of the functionality of the server, they need to be carefully managed and configured to minimize unwanted intrusion and logon possibilities.

When configuring security for Linux systems, use/etc/inittab files, runlevels, and one or two services to manage "superdaemons" such as inetd or xinetd direct Management services.

Inittab

The/etc/inittab file is used to initiate system services during the initialization of the system. On a configured system, although it typically does not include many services, many other services are loaded in the default installation of some Linux systems. The/etc/inittab file content is somewhat blurry, and it's important to make service management relatively simple.

First, you do not add a service to the system startup item by/etc/inittab file mode.

Second, do not remove the first field before the first colon in the/etc/inittab file as a single-precision number, or the previous portion of the entire login service. Lines that begin with a single digit can open the TTY console, which lists all the services before they are opened, and even lists their more important features. There may be some exceptions that are safe to do without altering it, especially if you are unsure.

Third,/etc/inittab is used for process management when importing and runlevel selection. Typically not used for normal system operations.

Finally, when importing, the RC system starts adding steps, not the INIT system. If you look at the contents of the/etc/inittab, you will notice that the login ends with a character such as RC0 to RC6. This is the instructions for initializing how the system handles Runlevels.

Runlevels

The operation of Linux operating systems can be managed through runlevels. Different runlevels are defined as having different behaviors, like Windows operating systems, which have normal operating mode, Safe mode, and in some cases DOS mode.

RunLevel 0 is used to turn off the system and it can power off the system if the soft power is properly set.

RunLevel 1 is a single-user network-free mode that is used for low-level troubleshooting and management operations.

RunLevel 2 to RunLevel 5 multiuser mode for normal system operation. Runlevel2 and 3 are command-line modes, 3 have network connections and 2 do not have a network connection. RunLevel 5 is used to start X windows to provide a graphical user interface.

RunLevel 6 is used for system reboots when the entire init system or even bootloader needs to be restarted.

Other runlevels are defined by the system administrator, but the "legacy" Unix system does not have this functionality. In this case, they cannot be defined and cannot be used.

At the shell, you can enter the RunLevel command to locate the previous renlevel and the current runlevel. If you do not change the system runlevel, the output of the command is uppercase n followed by the runlevel number, where n means no previous runlevel, and if you want to change runlevel, you can use the init command followed by the number of runlevel you want to use. For example, entering Init 6 indicates a reboot system, or init 1 enters single-user mode.

The procedure for configuring RunLevel is different for each version. For example, in a Debian gnu/linux system, service scripts located in/etc/init.d have links to them from the/ETC/RCN.D path, where n represents the runlevel number that needs to be configured. Symlinks that begin with the letter K indicate the program that was killed when entering the RunLevel, and the symlinks that begins with the letter S indicates the program that was started when it entered the runlevel. The larger the number value after the letter, from 1 to 99, indicates that the time to start or kill is higher.

Most RPM-based versions use the RC system used by Redhat. This system uses a more complex path structure than a Debian based system, and there is a big difference between different RPM based systems. More information on management RunLevel is provided on the instructions.