Is there any way to set up minimum passcode requirements, such as a minimum length, requirement of mixed case alphanumerics and at least 1 symbol in the passcode, and enforce that at passcode changes?
Password complexity in Ubuntu is controlled by PAM. Unfortunately, PAM is "typically Unix" like in its approach. Meaning that it spreads its configuration through a large number of very confusing files.
The file that controls password complexity is:
There is a line:
password [success=1 default=ignore] pam_unix.so obscure sha512
Which defines the basic rules for password complexity. You can add a minimum length override by changing it to:
password [success=1 default=ignore] pam_unix.so obscure sha512 minlen=12
or whatever minimum you want. As you can see, the default already defines some basic obscurity rules. These basic rules can be seen in:
Search for "obscure".
There are a large number of pam modules that can be installed.
apt-cache search libpam-
Should show you them.
You will need to hunt down the documenation for them I'm afraid. But the "cracklib" is a common addition.
UPDATE: I should have pointed out that the default "obscure" parameter includes tests for complexity based on previous passwords and simplicity (length, number of different types of character). The example in the manpage shows cracklib in action. Install libpam_cracklib to get that working.
Also, once you have worked out what to change, the changes are the same in other files so that you can enforce the same (or different) password checks for SSH and other applications.
Password values are controlled in the file
For more information on how to modify the file see pam_unix manpage
Pre-installed PAM modules allow you to set up basic requirements within the light of complexity. There is a nice module which is a successor of pam_cracklib module - pam_pwquality. In order to install it type the following
apt-get install libpam-pwquality
then get familiar with this one
especially with the "Options" section.
Now you can edit the common-password in /etc/pam.d/
find the line which contains the following "password requisite pam_pwquality.so" statement and after pam_pwquality.so attach your options like this
password requisite pam_pwquality.so minlen=16 ucredit=-4 retry=3
which stands for "the minimum size of password is 16 characters, where minimum 4 of them a uppercase. Prompt user for password 3 times.
pam_pwquality allows you make much more complex password requirements in combination with other modules like pam_pwhistory. Good luck