Книга: Linux Network Administrator Guide, Second Edition

Restricting call times

Restricting call times

Taylor UUCP provides a number of ways you may restrict the times when calls can be placed to a remote system. You might do this either because of limitations the remote host places on its services during business hours, or simply to avoid times with high call rates. Note that it is always possible to override call-time restrictions by giving uucico the -S or -f option.

By default, Taylor UUCP disallows connections at any time, so you have to use some sort of time specification in the sys file. If you don't care about call time restrictions, you can specify the time option with a value of Any in your sys file.

The simplest way to restrict call time is to include a time entry, followed by a string made up of a day and a time subfield. Day may be any combination of Mo, Tu, We, Th, Fr, Sa, and Su. You can also specify Any, Never, or Wk for weekdays. The time consists of two 24-hour clock values, separated by a dash. They specify the range during which calls may be placed. The combination of these tokens is written without white space in between. Any number of day and time specifications may be grouped together with commas, as this line shows:

time MoWe0300-0730,Fr1805-2200

This example allows calls on Mondays and Wednesdays from 3:00 a.m. to 7:30 a.m., and on Fridays between 6:05 p.m. and 10:00 p.m. When a time field spans midnight, say Mo1830-0600, it actually means Monday, between midnight and 6:00 a.m. and between 6:30 p.m. and midnight.

The special time strings Any and Never mean what they say: calls may be placed at any or no time, respectively.

Taylor UUCP also has a number of special tokens you may use in time strings, such as NonPeak and Night. These special tokens are shorthand for Any2300-0800,SaSu0800-1700 and Any1800-0700,SaSu, respectively.

The time command takes an optional second argument that describes a retry time in minutes. When an attempt to establish a connection fails, uucico will not allow another attempt to dial up the remote host within a certain interval. For instance, when you specify a retry time of 5 minutes, uucico will refuse to call the remote system within 5 minutes after the last failure. By default, uucico uses an exponential backoff scheme, where the retry interval increases with each repeated failure.

The timegrade command allows you to attach a maximum spool grade to a schedule. For instance, assume you have the following timegrade commands in a system entry:

timegrade           N Wk1900-0700,SaSu
timegrade           C Any

This allows jobs with a spool grade of C or higher (usually mail is queued with grade B or C) to be transferred whenever a call is established, while news (usually queued with grade N) are transferred only during the night and at weekends.

Just like time, the timegrade command takes a retry interval in minutes as an optional third argument.

However, a caveat about spool grades is in order here. First, the timegrade option applies only to what your systems sends; the remote system may still transfer anything it likes. You can use the call-timegrade option to explicitly request it to send only jobs above some given spool grade; but there's no guarantee it will obey this request.[97]

Similarly, the timegrade field is not checked when a remote system calls in, so any jobs queued for the calling system will be sent. However, the remote system can explicitly request your uucico to restrict itself to a certain spool grade.

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