View source for OS X password recovery

__NOTOC__
In general terms, before any specific step to change the password, we need to first 
# Boot on single-user mode
# Mount the system in read-write mode
 # /sbin/fsck -fy
 # mount -uw /

=== How to change a password on OS X 10.4 or older ===
Once the root filesystem is mounted r/w on single user mode, the procedure is as follows:
 # sh /etc/rc
 # passwd my_user

=== How to change a password on OS X 10.5 with no installation DVD ===
Once the root filesystem is mounted r/w on single user mode, the procedure is as follows:
# Launch the directory services
# Change/reset the password
# Reboot the system

In short, the list of commands are:
 # launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist
 # dscl . -passwd /Users/<username> <password>
 # reboot

=== How to change a password on OS X 10.8 with no installation DVD ===
Once the root filesystem is mounted r/w on single user mode, the procedure is as follows:
# Launch the directory services
# Change/reset the password
# Reboot the system

In short, the list of commands are:
 # launchctl load launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist
 # dscl . -passwd /Users/<username> <password>
 # reboot

=== How to change a password on XServe ===
Once the root filesystem is mounted r/w on single user mode, the procedure is as follows:
 # nicl -raw /var/db/netinfo/local.nidb -create /users/$newuser _writers_passwd administrator
 # passwd administrator
 # reboot

=== How to create a new user with administrative privileges ===
First write down the gid which comes from admin group
 # nicl -raw /var/db/netinfo/local.nidb -read /groups/admin

Lets say, the gid is '''''20''''', then from command line execute:
 # nicl -raw /var/db/netinfo/local.nidb -create /users/my_user
 # nicl -raw /var/db/netinfo/local.nidb -create /users/my_user uid my_user_id
 # nicl -raw /var/db/netinfo/local.nidb -create /users/my_user realname "My User Real Name"
 # nicl -raw /var/db/netinfo/local.nidb -create /users/my_user passwd "my_user_passwd"
 # nicl -raw /var/db/netinfo/local.nidb -create /users/my_user gid 20
 # nicl -raw /var/db/netinfo/local.nidb -create /users/my_user shell "/bin/bash"
 # nicl -raw /var/db/netinfo/local.nidb -create /users/my_user home "/Users/my_user"
 # nicl -raw /var/db/netinfo/local.nidb -create /users/my_user _writers_passwd my_user
 # passwd my_user
 # ditto /System/Library/UserTemplate/English.lproj /Users/my_user
 # chown -R my_user:staff /Users/my_user
 # nicl -raw /var/db/netinfo/local.nidb -read /users/my_user
 # nicl -raw /var/db/netinfo/local.nidb -append /groups/wheel users my_user
 # nicl -raw /var/db/netinfo/local.nidb -append /groups/admin users my_user