A dial-up password is an additional password required of users who access the computer through a modem or dial-up port. The correct password must be entered before the user is granted access to the computer.
d_passwd is an ASCII file which contains a list of executable programs (typically shells) that require a dial-up password and the associated encrypted passwords. When a user attempts to log in on any of the ports listed in the dialups file (see dialups(4)), the login program looks at the user's login entry stored in the passwd file (see passwd(4)), and compares the login shell field to the entries in d_passwd. These entries determine whether the user will be required to supply a dial-up password.
Each entry in d_passwd is a single line of the form:
login-shell The name of the login program that will require an additional dial-up password.
password An encrypted password. Users accessing the computer through a dial-up port or modem using login-shell will be required to enter this password before gaining access to the computer.
d_passwd should be owned by the root user and the root group. The file should have read and write permissions for the owner (root) only.
If the user's login program in the passwd file is not found in d_passwd or if the login shell field in passwd is empty, the user must supply the default password. The default password is the entry for /usr/bin/sh. If d_passwd has no entry for /usr/bin/sh, then those users whose login shell field in passwd is empty or does not match any entry in d_passwd will not be prompted for a dial-up password.
Dial-up logins are disabled if d_passwd has only the following entry:
Example 1: Sample d_passwd file.
Here is a sample d_passwd file:
/usr/lib/uucp/uucico:q.mJzTnu8icF0: /usr/bin/csh:6k/7KCFRPNVXg: /usr/bin/ksh:9df/FDf.4jkRt: /usr/bin/sh:41FuGVzGcDJlw:
The passwd (see passwd(1)) utility can be used to generate the encrypted password for each login program. passwd generates encrypted passwords for users and places the password in the shadow (see shadow(4)) file. Passwords for the d_passwd file will need to be generated by first adding a temporary user id using useradd (see useradd(1M)), and then using passwd(1) to generate the desired password in the shadow file. Once the encrypted version of the password has been created, it can be copied to the d_passwd file.
1. Type useradd tempuser and press Return. This creates a user named tempuser.
2. Type passwd tempuser and press Return. This creates an encrypted password for tempuser and places it in the shadow file.
3. Find the entry for tempuser in the shadow file and copy the encrypted password to the desired entry in the d_passwd file.
4. Type userdel tempuser and press Return to delete tempuser.
These steps must be executed as the root user.
/etc/d_passwd dial-up password file
/etc/dialups list of dial-up ports requiring dial-up passwords
/etc/passwd password file
/etc/shadow shadow password file
passwd(1), useradd(1M), dialups(4), passwd(4), shadow(4)
When creating a new dial-up password, be sure to remain logged in on at least one terminal while testing the new password. This ensures that there is an available terminal from which you can correct any mistakes that were made when the new password was added.