Setuserpasswd command
From DD-WRT Wiki
Change the username and password used to log into the Web Interface.
usage: setuserpasswd [username] [password]
e.g.
root@DD-WRT:~# setuserpasswd myuser mypassw0rd
Notes:
- This command automatically commits changes into nvram.
- Telnet/SSH username will remain root!
- Telnet/SSH password may not take effect immediately. In this case also run the setpasswd command.
- The username and password are stored securely in nvram variables, hashed with salt.