Cơ sở kiến thức

Overview

This article outlines the procedure for suppressing low-level kernel messages, including iptables logs, from displaying on the system console. Adjusting the kernel.printk parameter controls the verbosity of kernel logging output.

Prerequisites

• Root or sudo access is required to modify system configuration files and apply runtime parameters.

Permanent Configuration

To persistently disable console logging across reboots, update the sysctl configuration:

1. Edit the /etc/sysctl.conf file using a text editor.
2. Add or modify the following line to configure the log levels:

kernel.printk = 4 1 1 7

Save the file. The changes will automatically apply upon system reboot. To apply them immediately without restarting, execute:

/sbin/sysctl -p /etc/sysctl.conf

Temporary Configuration

To apply the logging change for the current session only (settings will revert after a reboot), run the following command:

echo "4 1 1 7" > /proc/sys/kernel/printk

Verification

To confirm that the new logging levels are active, check the current configuration:

cat /proc/sys/kernel/printk

The output should return 4 1 1 7.

Troubleshooting

• Permission Denied: Ensure all commands are executed with root privileges. Writing to /proc/sys/kernel/printk requires elevated access.
• Changes Not Persisting: Verify that the entry was correctly added to /etc/sysctl.conf and that no syntax errors exist in the file before running /sbin/sysctl -p /etc/sysctl.conf.
• Unexpected Output Values: If the verification command returns values other than 4 1 1 7, another service or script may be overriding the kernel parameters at runtime.