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Linux log files are stored in plain-text and can be found in the /var/log directory

tail /var/log/syslog # Shows the last part of the logs, where problems usually lie.

Essential Linux Log Files:

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/var/log/daemon.log - Tracks services running in the background that perform important tasks, but has no graphical output

3. Application Logs (examples)

/var/log/apache2/ - Apache HTTP server logs (access, error).

/var/log/mysql/ - MySQL database server logs.

/var/log/apt directory - contains several log files that provide important information about apt-related activities on Debian-based systems.

/var/log/yum.log - Red Hat-based systems store the yum and dnf package manager logs, file provides information about the results of a specific command, such as any errors or warnings that were generated. For example, if a package update fails.

Useful commands:

journalctl # Views systemd logs and allows filtering Linux system logs to extract relevant information for monitoring and troubleshooting. How To Use journalctl

journalctl # Views systemd logs and allows filtering Linux system logs to extract relevant information for monitoring and troubleshooting. How To Use journalctl

 journalctl

-- Logs begin at Tue 2024-06-18 10:55:23 UTC, end at Tue 2024-06-

 journalctl

-- Logs begin at Tue 2024-06-18 10:55:23 UTC, end at Tue 2024-06-18 12:06:19 UTC. --
Jun 18 10:55:23 hostname kernel: Linux version 5.4.0-74-generic (buildd@lcy01-amd64-013) (gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04)) #83-Ubuntu SMP Thu May 6 10:34:06 UTC 2021 (Ubuntu 5.4.0-74.83-generic 5.4.101)
Jun 18 10:55:23 hostname kernel: Command line: BOOT_IMAGE=/boot/vmlinuz-5.4.0-74-generic root=UUID=5d7f5dcd-1234-5678-9abc-def012345678 ro quiet splash vt.handoff=7
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 journalctl -u apache2

-- Logs begin at Tue 2024-06-18 10:55:23 UTC, end at Tue 2024-06-18 12:05:19 UTC. --
Jun 18 11:56:19 hostname systemd[1]: Starting The Apache HTTP Server...
Jun 18 11:56:19 hostname apache2[1342]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message
Jun 18 11:56:19 hostname systemd[1]: Started The Apache HTTP Server.

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3. Application Logs (examples)

/var/log/

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apache2/ - Apache HTTP server logs (access, error).

/var/log/mysql/ - MySQL database server logs.

/var/log/apt directory - contains several log files that provide important information about apt-related activities on Debian-based systems.

/var/log/yum.log - Red Hat-based systems store the yum and dnf package manager logs, file provides information about the results of a specific command, such as any errors or warnings that were generated. For example, if a package update fails

4. Event Logs

var/log/wtmp - Records of user logins and logouts.

var/log/lastlog - Information about the last logins for all users. This binary file can be read by command lastlog.

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.home-banner {
                    background: #459df0;
                    color: #fff;
                    font-size: 20px;
                    padding: 20px;
                    }
                    .home-banner h2 {
                    color: #fff;
                    }
                    .title-box {
                    border: 1px none #459df0;
                    padding: 10px;
                    }
                    .title-box > h2 {
                    background: #459df0;
                    bottom: 10px;
                    color: #fff;
                    margin-left: -10px;
                    margin-right: -10px;
                    padding: 2px 10px;
                    position: relative;
                    }

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