Comparing two directory structures

 Sometimes when I'm copying important directory structure (with cp -rp) I want to make sure that each and every file was copied correctly, so I compare source directory structure with it's copy this way:

DIRR=<copied-dir-structure>; diff -u <(cd <path-where-source-dir-lies>; find "$DIRR" -type f -exec ls -al {} \;) <(cd <path-where-copied-dir-lies>; find "$DIRR" -type f -exec ls -al {} \;)

SSH local port forwarding

Recently I advised on serverfault.com how to do local port forwarding with ssh:

On remote machine with sshd server, start a service that you would like to give access to:

 echo "hello" | nc -l -p 2222

On local machine initiate port forwarding:

 ssh -L 1234:localhost:2222 root@remoteserver.com

try it (from local machine):

 nc localhost 1234

If you will see "hello" that means port forwarding worked as expected.

 Use cases for this kind of functionality:
 - tunneling otherwise insecure TCP traffic
 - accessing services behind firewall when only sshd access is available