Setpasswd command
From DD-WRT Wiki
The setpasswd command recreates the /etc/passwd file so that the password to log into SSH/Telnet will match the password for the Web administration GUI.
usage: setpasswd (no arguments)
Usually this occurs automatically when the password is changed using the GUI or [setuserpasswd], so setpasswd is not needed. You can check by comparing the hashed password in the NVRAM setting to the /etc/passwd file:
root@DD-WRT:~# nvram get http_passwd $1$tmuJ6dMD$7dOhWGU3L8LzeMNyDmndg0 root@DD-WRT:~# cat /etc/passwd root:$1$tmuJ6dMD$7dOhWGU3L8LzeMNyDmndg0:0:0:Root User,,,:/tmp/root:/bin/sh reboot:$1$tmuJ6dMD$7dOhWGU3L8LzeMNyDmndg0:0:0:Root User,,,:/tmp/root:/sbin/reboot