Linux / UNIX: Generate Passwords

How do I generate random passwords under Linux / UNIX / Mac OS X and *BSD operating systems?

You can use the following command to generate the random password:

tr -dc A-Za-z0-9_ < /dev/urandom | head -c 16 | xargs

Sample outputs:

1z2G4SVmZOdd4uK4

You can create a bash shell function as follows (add to your ~/.bashrc):

 
genpasswd() {
 local l=$1
        [ "$l" == "" ] && l=16
       tr -dc A-Za-z0-9_ < /dev/urandom | head -c ${l} | xargs
}
 

Now use genpasswd as follows to create 8 character long password:
genpasswd 8
Sample outputs:

Es5Yzf8H