Dangerous Grep
If you’re in the root folder of your filesystem, don’t type grep -r “some stuff to search for” *. Why? Because you’ll get a message like “grep: memory exhausted” and your system won’t respond (at least it won’t respond to ssh, http, smtp, etc). Actually, it appears it just crashes the network port. Executing a simple ifdown eth0 followed by an ifup eth0 from the console appeared to solve the problem. Then again, if you’re like me and your server is housed 20 minutes away and this happens at midnight it’s a little inconvenient to go access the server.
Why does this happen? Well, apparently grep keeps appending to its buffer until it comes across a newline character ‘\n’, at which point it clears the buffer and starts reading from the next line. This is a problem when it tries to search a large binary file (like something in /dev or /proc). I should have known better and excluded /dev and /proc to begin with, or even better run the command inside a subfolder such as /etc (which is probably all I needed to search). I’ll remember that next time. Still, after this, I’m nervous about executing a grep command. What if it comes across some large binary file I didn’t anticipate. I’m thinking of writing a simple shell script and add it to cron to run every fifteen minutes to cycle the network interface if it can’t ping the gateway. I think that should take care of it, but that solution seems a little hackish. Anyway, I’m open to suggestions for a better one.