At some point you want to know what packets are flowing on your network. Use tcpdump for this. The man page is obtuse, to say the least, so here are some simple commands to get you started. -n means show IP numbers and don't try to translate them to names. -l means write a line as soon as it is ready. -i eth0 means trace the packets flowing through the first ethernet interface. src or dst w.x.y.z traces only packets going to or from IP address w.x.y.z. port 80 traces only packets for HTTP. proto udp traces only packets for UDP protocol. Once you are happy with each option combine them with 'and' 'or' 'not' to get the effects you want.

This command creates a file of arbitrary size in a windows environment. Show Sample Output

"-o loop" lets you use a file as a block device

Credit goes here: http://blag.xkcd.com/2008/12/03/some-lists/ Show Sample Output

...can do similar w/ tar, dd, xfsdump, e2fsdump, etc.

e.g. fuser 25/tcp (see which pid is listening on smtp)

The two lines below are for a BeanShell script so it can be executed under Linux and Cygwin. Also, bsh.jar must be in the CLASSPATH environment variable, or in the jre/lib/ext/ directory of the JVM. #! /bin/sh ///bin/true; exec java bsh.Interpreter "$0" "$@"

Does an 'ls' on just the files and directories in the current directory with an execute bit turned on. This version will list directories. Just tack on "-type f" to the start of the find to omit listing directories and list only files.

Substitute nano with your favorite editor, of course.

Or "tail -r" on Solaris.

a pkcs8 key will have integer 00 at offset 4 and an rsaEncryption object at offset 9

This command will start a simple SMTP server listening on port 1025 of localhost. This server simply prints to standard output all email headers and the email body.

changes group ownership of all files/dirs in /path/to/dir to a project group [projgroup] and then gives the sgid bit to directories in that tree - all subsequently created files will inherit [projgroup]'s gid.