How to dump the dmesg AKA Kernel logs to a single .txt file from the kernel boot?

There is a command called dmesg which will print the logs to stdout. You can just redirect stdout to a text file.

dmesg > /path/to/dmesg.txt 

You could extend this. A really useful option would be to add a line to your ~/.profile file (in your home directory) which appends the output of dmesg on login. Simply add a line which says:

dmesg >> /path/to/dmesg.txt 

If you just want the first few lines (0.000000 messages) you can pipe it into head like so.

With stdout:

dmesg | head 

or with head on an already saved .txt file.

head /path/to/dmesg.txt 

That's pretty much it, hope this helps!

EDIT: BTW, this does contain the 0.000000 messages

You can use:

cat /var/log/dmesg > file.txt 

and use:

head /var/log/dmesg 

if you want to see the first lines of dmesg.

See too 'man head' for more specifications. The '>' symbol redirect the ouput of 'cat' to the 'file.txt'