Linux operation and maintenance log files - common log files, services to manage log files

Almost all services on Linux have log files. Log files are used to record the running status of the software. Through log files, we can obtain a lot of useful information. For example, through nginx log files, we can count the daily IP number, pv number, etc. of the website. In addition, if there is a problem with the software running, we can also use the log file information to locate the source of the error. Therefore, log files are also an important part of the software.

Common log files

In the Linux system, many useful log files are recorded in the /var/log/ directory.

• /var/log/cron records information related to scheduled tasks

• /var/log/dmesg boot kernel information

• /var/log/btmp records error login information. This file cannot be viewed through vi, but can be viewed with the lastb command.

• /var/log/lastlog records the last login status of each user. This file cannot be viewed through vi. Use the lastlog command to view it

• /var/log/maillog records email information

• /var/log/message records important system information

• /var/log/recure Record verification and authorization information. As long as the program involves the account number and password, it will be recorded

• /var/log/wtmp. It will permanently record the user’s login and exit information. In addition, it will also Record shutdown, restart, and boot information. Use the last command to view

• /var/log/ulmp to record the current logged in user information. You can use the w and who commands to view

Services related to log files

Regarding the generation of log files, the main There are two ways, one is to generate log information by the software itself, such as apache and nginx software, and the other is to generate log information through the log related services of the Linux system. For system management log software, there are three main ones:

• systemd-journald.service

• rsyslog.service

• logrotate

#Basically, for services managed by systemd, some information generated during the startup and running processes will be recorded in binary format by systemd-journald (stored in memory), and then send the information to rsyslog for further recording. As for the logrotate service, it is used to cut and rotate logs to prevent a single log file from being too large and too many log files.

So, the division of labor for the above three services is as follows. First, systemd-journald obtains the information and records it in the memory. Then it sends the information to rsyslog, and rsyslog will store the information in the log file. Finally, Use logrotate to rotate log files.

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