dmesg Linux Command Guide
The dmesg command in Linux is used to display kernel ring buffer messages. It can help diagnose hardware issues, view system boot messages, and troubleshoot system problems. By default, dmesg shows the most recent kernel messages. With various options, users can filter messages, display timestamps, and more.
dmesg Syntax:
Section titled “dmesg Syntax:”dmesg [options]Options:
Section titled “Options:”| Option | Description |
|---|---|
| -c | Clear the ring buffer after printing. |
| -s | Set the buffer size for the kernel log. |
| -l | Restrict output to the given log level. |
| -n | Set the level of messages shown. |
| -H | Human-readable output. |
| -T | Include timestamps in the output. |
| -D | Show timestamps in readable format. |
| -x | Show hexadecimal and ASCII representation of the message buffer. |
| -w | Wait for new messages to appear. |
| -d | Show all kernel messages. |
| —color | Colorize the output. |
Parameters:
Section titled “Parameters:”There are no specific parameters for the dmesg command.
dmesg Command Samples:
Section titled “dmesg Command Samples:”Display the most recent kernel messages
Section titled “Display the most recent kernel messages”dmesgThis command displays the most recent kernel messages.
Display kernel messages with a timestamp
Section titled “Display kernel messages with a timestamp”dmesg -TShows kernel messages with human-readable timestamps.
Show only kernel messages related to the memory
Section titled “Show only kernel messages related to the memory”dmesg | grep memoryFilters the kernel messages to display only those related to memory.
Display messages of a specific log level
Section titled “Display messages of a specific log level”dmesg -l errShows kernel messages with a certain log level, in this case “error” messages.
Save kernel messages to a file
Section titled “Save kernel messages to a file”dmesg > kernel_messages.txtRedirects the kernel messages output to a file named “kernel_messages.txt”.
Watch kernel messages in real-time
Section titled “Watch kernel messages in real-time”dmesg --followAllows watching kernel messages in real-time as they are generated.
Show the number of kernel messages
Section titled “Show the number of kernel messages”dmesg -c | wc -lCounts and displays the number of kernel messages currently in the buffer.
dmesg FAQ:
Section titled “dmesg FAQ:”How do I use dmesg in Linux?
Section titled “How do I use dmesg in Linux?”To use the dmesg command in Linux, execute the following command:
dmesgHow can I display the last 20 lines of kernel messages using dmesg?
Section titled “How can I display the last 20 lines of kernel messages using dmesg?”To display the last 20 lines of kernel messages in Linux with dmesg, use the following command:
dmesg | tail -n 20How can I search for specific keywords in kernel messages using dmesg?
Section titled “How can I search for specific keywords in kernel messages using dmesg?”To search for specific keywords in kernel messages using dmesg in Linux, you can use the grep command along with dmesg. For example:
dmesg | grep "usb"How can I clear the kernel ring buffer using dmesg?
Section titled “How can I clear the kernel ring buffer using dmesg?”To clear the kernel ring buffer in Linux using dmesg, use the following command:
sudo dmesg -cHow can I view kernel messages in real-time using dmesg?
Section titled “How can I view kernel messages in real-time using dmesg?”To view kernel messages in real-time in Linux using dmesg, you can use the -w option. Execute the following command:
dmesg -wHow can I save kernel messages to a file with timestamps using dmesg?
Section titled “How can I save kernel messages to a file with timestamps using dmesg?”To save kernel messages to a file with timestamps in Linux using dmesg, you can use the --ctime option along with redirection. Here’s an example:
dmesg --ctime > kernel_logs.txtApplications of the dmesg command
Section titled “Applications of the dmesg command”- Display kernel ring buffer messages
- Troubleshoot hardware and driver issues
- Check for system initialization errors
- View system boot messages
- Debug device detection and driver loading issues