Upon logging onto UNIX for the first time, it is STRONGLY recommended that the user changes his/her password, using the passwd command:
passwd
UNIX will ask for the old password, then the new one (twice), always with the echo turned off.
Some systems will provide restrictions on the password: SunOS 4.0.3 will accept five-character-long passwords if in mixed case. The recommended minimum length is six characters.
Also note that a maximum length of eight characters is used by the password algorithm: any password longer than eight characters will be truncated to eight.