Installing and Administering PPP

Chapter 2 37

Setting Up PPP Connections

Conﬁguring Inbound Connections

On machines that only accept incoming calls, pppd does not need to be

started at boot time, since pppd is started when a PPP login occurs.

Machines that both initiate and receive calls must start pppd at boot

time, and must also prepare accounts for incoming connections. User

accounts must be created in the /etc/passwd ﬁle for the system to be

able to accept incoming calls.

When the local system receives a login, it does the following:

1. Veriﬁes the password by comparing it to the entry in the

/etc/passwd ﬁle.

2. If the login is successful, the Login shell script is run. Login starts

pppd on the local system which will communicate with the pppd on

the peer. The two pppd’s will negotiate and establish a PPP

connection.

/etc/passwd

The following is an example of an entry that would be made to lark's

/etc/passwd ﬁle:

Probin::105:42:Robin's PPP login:/etc/ppp:/etc/ppp/Login

The '105' in the password entry is a unique user ID (uid) for this PPP

lark's /etc/group ﬁle.

Create a password for robin’s login:

# passwd Probin

New password: some password

Retype new password: some password

Note that a PPP user's login shell script can be located anywhere and

named whatever you choose. For purposes of this illustration, the login

script will be /etc/ppp/Login.