PeterWhen you're having hardware problems, or just trying to work out why something's not working under Linux, or any Unix-like operating system, logs can be invaluable sources of information.
Specific applications (like the Apache web server, for example) will often keep their own log files, but there are also system-wide logs that can help you as a power user or an administrator to track down issues.
First of all, if it's a hardware problem you're having, then check out dmesg. From the man page:
dmesg - print or control the kernel ring buffer
To invoke dmesg, simply type it at a terminal:
$ dmesg
Often there can be quite a lot of output, so to only show the last 10 lines, pipe the output to tail, like so:
$ dmesg | tail
That usually throws up some useful information if you're having a hardware issue. Even if you're not a power user and you're seeking help, posting the output of dmesg | tail can help anyone who's helping you to diagnose the problem.
And finally, there is also the /var/log/messages file. This often contains more software-specific errors or warnings, but is equally useful in trying to figure out why something isn't working.
Usually you need to be root to read the file, so you'll need to either run su - in your terminal first, or prefix the command with sudo.
# tail /var/log/messages
That will show you the last 10 lines of the file. If you want to see the whole thing, you can use other commands on the /var/log/messages file (like cat or perhaps less if you want to scroll through it).
So next time you need to ask someone help with your Linux problem, give them the output of these two commands and it might speed up your solution!
