On a Debian-based Linux system, such as Ubuntu, you can record the boot messages by using the dmesg command. The dmesg command displays the kernel ring buffer, which is a log of kernel messages that are generated during the boot process.
To record the boot messages, you can use the dmesg command and redirect the output to a file. For example:
dmesg > boot.log
This will save the boot messages to a file called boot.log in the current directory.
You can also use the dmesg command with the -T option to display the timestamp of each message. For example:
dmesg -T > boot.log
This will include the timestamp of each message in the output, which can be useful for debugging purposes.
You can also use the journalctl command to view the system journal, which contains log messages from the system and all system services. To view the journal, you can run the following command:
journalctl
To save the journal to a file, you can use the --output option and specify the file to save the output to. For example:
journalctl --output=boot.log