Master system management and become a full-fledged Linux user

Acquisition of administrator knowledge is indispensable for utilization

　UNIX-like operating systems such as Linux are originally created on the assumption that they will be used in a multi-user environment in which multiple users use one system at the same time. UNIX-like OS users are classified into two types: system administrators (superusers) who can operate all files and commands inside the system, and general users who can use only the functions permitted by the system administrator. Only superusers can make settings related to the entire system linux system administrator roles and responsibilities.

　Once you have Linux installed on your PC, you will be superuser when making various settings. For example, when performing basic tasks necessary to utilize a PC, such as enabling a printer or compiling source files and installing software, the system administrator's authority (root authority) is set. It will be necessary to acquire and operate it.

Important even when only you use it

　In this way, even if you have only one Linux-equipped machine, you can perform various operations with root privileges. There is no problem if the system becomes unusable as long as you try installing Linux, but when you start using the system in earnest, it is essential to acquire knowledge about operation management and how to use various commands related to it. ..

　Let's assume that your foot is caught in the power cable and the power of the Linux-equipped machine in operation is cut off. In that case, turning on the power does not always restore the system to its original state. In some cases, you will lose important data on your hard disk. Even then, if you know how to use the commands to check and repair your hard disk, you can usually restore your system to its original state.

　In particular, when using a Linux-equipped PC for server purposes, it is more important to acquire knowledge of system management. If it is used as a server, the system must be constantly monitored to maintain the stable provision of the services provided by the server, such as the functions of a Web server and file / print server. Recently, Linux servers are often used for systems such as Web servers that are premised on connecting to the Internet. In such cases, system management skills are required to prevent unauthorized intrusion and unauthorized use. When installing a server, the system construction work is exhausted and attention is not paid to system management, but I would like to keep in mind that system management will be the most important work after construction.

Operation management work contents and necessary skills

　Even if you say operation management in a nutshell, the work content is diverse. The main work contents can be roughly classified into three as shown in Fig. 2 [ Enlarged display ].

　The general administrator's task is to set up the system, provide services to expected users, monitor whether the services are being provided stably, and at the same time back up data etc. in case of a failure. .. Of course, in the unlikely event that a problem occurs, it is necessary to quickly remove the failure and restore the backup data.

　As you can see from the work contents, there are some management tasks that should be performed on a daily basis and some that are performed as needed. What you do on a daily basis should be done weekly or daily, such as system monitoring and backup. Use cron or shell scripts to automate these tasks as much as possible to reduce the workload. Otherwise, tasks such as resource monitoring and log checking tend to be neglected when busy with tasks to be performed as needed.

　System settings and restores are performed as needed. For example, when a system user is changed due to a personnel change, it becomes necessary to delete an existing user or add a new user.

　These tasks are required in general system management, and there is nothing special about Linux-equipped machines. However, system administrators of Linux-equipped machines are required to acquire Linux-specific know-how to some extent, and need to pay particular attention to the handling of free software including Linux.

　Linux-specific know-how is required mainly because the resource-related accounting information * 1 held by the Linux kernel is different from that of commercial UNIX, and the mechanism by which the OS operates is different.

　For example, vmstat, a command that displays the load factor and usage status of the main memory and CPU, is provided in both Linux and commercial UNIX, but the output content when the command is executed is slightly different. Therefore, as will be described later, the status of the main memory cannot be grasped correctly without knowing the memory management mechanism of Linux.

　Also, in a system equipped with Linux, unlike the case of using commercial UNIX, the OS itself is free software, and the applications used are often free software. Security patches and upgraded versions of these free software are frequently provided, so it is important to always check such information.

Let's formulate an operation policy

　It is important to formulate a system operation policy properly in system management. The operation policy is a summary of the purpose of the system, user target, usage pattern, management system, etc. ( Fig. 3 [ enlarged view ]). As an example, consider the case of launching a web server. At that time, clearly decide who will use the Web server and how, and who will create the content of the Web. In line with that policy, the specific contents of system management such as user settings, system settings such as access privileges for files in the system, processes and logs that must be constantly monitored, and files to be backed up are determined.

　In this way, especially for server applications, it is not possible to determine specific procedures for system management work without a solid operation policy, and there is a possibility that security deficiencies will occur. Prior to system management, let's first formulate an appropriate operation policy.