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Watch is a very useful command for periodically running another command - in this using mysqladmin to display the processlist. This is useful for monitoring which queries are causing your server to clog up.
If your web server is down, this command will periodically attempt to connect to it. If the output is blank, your server is not yet up. If you see HTML, your server is up. Obviously, you need to replace the Google URL with your web server URL...
* 'watch' -- a command for re-executing a command and displaying
* '-n 15' -- tells watch to redo the command every 15 seconds
* 'curl' -- a handy utility for getting the source of a web page
* '-s' -- tells curl to be silent about failing
* '--connect-timeout 10' -- Try to connect for 10 seconds
This command repeatedly gets the specified process' stack using pstack (which is an insanely clever and tiny wrapper for gdb) and displays it fullscreen. Since it updates every second, you rapidly get an idea of where your program is stuck or spending time.
The 'tac' is used to make the output grow down, which makes it less jumpy. If the output is too big for your screen, you can always leave the 'tac' off to see the inner calls. (Or, better yet--get a bigger screen.)
Caveats: Won't work with stripped binaries and probably not well with threads, but you don't want to strip your binaries or use threads anyway.
This runs the uptime command every 30 seconds to avoid an SSH connection dropping due to inactivity. Granted there are better ways of solving this problem but this is sometimes the right tool for the job.