Login to the server running Open Directory and run the following to be prompted to change snoopdog’s password
sudo passwd -i OpenDirectory -l /LDAPv3/127.0.0.1 -u diradmin snoopdog
found here: https://discussions.apple.com/thread/1509269
passwd — modify a user’s password
passwd [-i infosystem [-l location]] [-u authname] [user]
The passwd utility changes the user’s password. If the user is not the super-user, passwd first prompts for the current password and will not continue unless the correct password is entered.
When entering the new password, the characters entered do not echo, in order to avoid the password being seen by a passer-by. The passwd utility
prompts for the new password twice in order to detect typing errors.
The new password should be at least six characters long and not purely alphabetic. Its total length should be less than _PASSWORD_LEN (currently 128
characters), although some directory systems allow longer passwords. Numbers, upper case letters, and meta characters are encouraged.
Once the password has been verified, passwd communicates the new password to the directory system.
This option specifies where the password update should be applied. Under Mac OS X 10.5 and later, supported directory systems are:
PAM (default) Pluggable Authentication Modules.
A system conforming to Open Directory APIs and supporting updates (including LDAP, etc). If no -l option is specified, the search node is used.
file The local flat-files (included for legacy configurations).
nis A remote NIS server containing the user’s password.
This option causes the password to be updated in the given location of the chosen directory system.
location may be a file name (/etc/master.passwd is the default)
location may be a NIS domainname
location may be a directory node name
location is not used
This option specifies the user name to use when authenticating to the directory node.
user This optional argument specifies the user account whose password will be changed. This account’s current password may be required, even when
run as the super-user, depending on the directory system.
/etc/master.passwd The user database
/etc/passwd A Version 7 format password file
/etc/passwd.XXXXXX Temporary copy of the password file
chpass(1), login(1), dscl(1), passwd(5), pwd_mkdb(8), vipw(8)
Robert Morris and Ken Thompson, UNIX password security.
A passwd command appeared in Version 6 AT&T UNIX.
Mac OS X August 18, 2008 Mac OS X
DSCL and scripting mentioned here: https://technology.siprep.org/terminal-command-to-change-a-user-password-on-a-mac/