login - Sign on
The login program is used when a user initially signs on, or it may be used at any time to change from one user to another without having to disconnect.
After a normal system startup sequence, the login program is executed. Its job is to answer the phone when remote callers dial the system, prompt them for a login code and password, and then allow them into the system if the codes are valid. While waiting for a call, it displays the current time on the screen. Login is also responsible for handling scheduled cron tasks.
While waiting for a call, the console operator can instruct login to process a command by pressing the ‘!’ key. Login reads a command line from the operator and executes the first command passing forward any arguments. For example, entering “!ctime” causes login to run the ctime program as a process. When ctime exits, control returns to login.
Other keys that login recognizes while waiting are:
Allows the operator to log into the system locally
Toggles the screen saver on and off
Exit to BASIC
In addition, certain keys can be configured to invoke macro commands to perform a variety of functions without actually having to login. See the Resources section of this manual entry for more details.
Login includes an internal task manager called cron which runs once a minute. Cron scans the file $/etc/crontab for tasks to perform at certain times and executes them in a way similar to the ‘!’ command for local console commands. (See cron for more details).
Any processes that login invokes are logged with the date and time of execution, including elapsed time. Local console processes are labeled “local” while cron processes are labeled “cron” in $spool/logs/syslog.
Unless otherwise instructed (see Resource File below), login answers a call on the first ring and attempts to connect. The connection speed is verified with a required rate, if specified. If the connection is slower than desired, the $/etc/lowbps file is displayed, and login disconnects to wait for another call.
After login answers a ringing phone line and successfully connects with another computer, it displays the file $/etc/herald. This file contains the name and location of the host system. The caller is prompted to enter a valid login name.
After a valid login name is given, login scans $/etc/passwd for a matching entry. Once found, the information for that account is read in. If the account is a non-root user, and the file $/etc/nologin exists, login prints its contents on the user’s terminal and disconnects. This stops users from logging in when the system is about to go down, or when it is closed to user traffic.
If the interpreter entry for the login is a quoted message, it is displayed, and the caller is prompted to enter a login name again. (e.g., a “help” login attempt might display a short message for signing on using a public account. Use adduser to create a “help” login which would display the quoted message given as the interpreter).
Next, login prompts the caller for a password, if appropriate. Echoing is turned off during the typing of the password, so it will not appear on any written record of the session. However, if the encrypted password in the entry deciphers to “none”, password input is bypassed. This is usually the case for guest logins.
The user has three attempts to enter a valid login name and matching password. If the caller fails, the file $/etc/badlogin is displayed, and login disconnects. Badlogin contains information on how to contact the system administrator for assistance, or may offer instructions for using a public account.
If all is well, the user is shown the previous sign on date, the message of the day file ($/etc/motd), and if a guest, the welcome file ($/etc/welcome). Login then executes a command interpreter according to the user’s password file entry. The current working directory will be set to the user’s home directory.
While login is waiting for a call or a command, it blacks out the local console display after a period of inactivity. This prevents images from “burning” into the screen. If a call comes in, a key is pressed, or a cron task starts up, the screen is restored. The time is displayed at random positions while the screen is blank.
Certain features of login can be adjusted by editing $/etc/rsrc/login.rsrc. The format of the file is described by the following sample entries in the order required (with comments added):
Seconds before the screen blanks. Zero seconds disables the screen saver.
Normally left blank, this line may contain a command line that is executed whenever a caller logs out or a cron task completes. By default, no command line tells login to scan for any letters that need delivering, and if found it executes sendmail. Typically, a command line would start with csh and the name of a shell script that contains a list of commands to execute, including sendmail.
Speaker control. This feature allows you to control the modem’s speaker via joystick position control. If this entry is 1, the direction of the joystick affects the modem’s speaker output during connections. Positioned to the left, the speaker remains silent.
Lowest connect speed allowed. If a caller connects at a speed lower than this value, $/etc/lowbps is displayed, and login disconnects.
Console availability hold time. This is a feature for Apple IIGS hosts only. This feature allows the administrator to lock the Caps Lock key while the system is in use. When the system becomes available, a series of beeps (the number determined by this entry’s value) is emitted, holding the system until there is a keyboard response. Unlocking the Caps Lock key, or setting this entry to 0, disables this feature.
Macro command keys. Each letter in this line corresponds to subsequent
lines that expand the macro key into commands. That is, the first line
following this one is for the ‘!’ character. The second is for the ‘c’
character, and so on. The macro lines must follow in the order that the
characters are given. Up to 26 macros may be defined. Shown here are the
defaults with comments in parenthesis (omit the comments):
(for "!" -- usually nothing) csh -c (for "c") mail (for "m") poll (for "p") boot -q (for "q") scan -l (for "s")
Pressing ‘q’ at the Waiting prompt expands into the “boot -q” command. This is because ‘q’ is the fifth character in the first line of macro keys, and “boot -q” is the fifth line following. You can change or edit the command line, then execute it by pressing RETURN. You can, of course, add, delete, or change any these macros.
Console cancel key (ASCII). The default console cancel key is Control-C (ASCII 3). This can be changed to any other character from ASCII 0 to 127. This cancel key is used whenever a macro is invoked.
No answer flag. If set to 1, causes login to ignore any incoming calls. It simply prevents the system from answering, allowing the modem to remain operational for outgoing calls only.
Command line time-out. This value (in seconds) sets the duration of inactivity at the Waiting command line prompt. If zero, no inactivity checking is performed.
This line, normally blank, contains a comma-separated list of account names that triggers a unique alert sequence. When a user signs on whose login name is in this line, a series of beeps is generated at the console. Then a second set of beeps follow, unique to that user. You can distinguish certain users from others without having to look at the console. This is useful for alerting you to troublesome callers.
“Login incorrect,” if the name or the password is bad.
“Account overdrawn,” when a caller has used up his monthly time allotment.
”File or directory not found,” when the specified user’s directory or interpreter to launch cannot be found.
adduser(ADM), cron(ADM), csh(C), passwd(C), plush(C), setenv(C)