crontab entry environment variables [PSARC/2007/503 FastTrack timeout 09/10/2007]

[Darren J Moffat]

I'm sponsoring this OpenSolaris case for Chris Gerhard. It has some possible
standards impact but I believe based on previous discussions this should
be acceptable, if it wasn't for the standards impact this would likely have
been self-review.

Template Version: @(#)sac_nextcase 1.64 07/13/07 SMI
This information is Copyright 2007 Sun Microsystems
1. Introduction
    1.1. Project/Component Working Name:
	 crontab entry environment variables
    1.2. Name of Document Author/Supplier:
	 Author:  Chris Gerhard
    1.3  Date of This Document:
	03 September, 2007
4. Technical Description

This project proposes support for and use of TZ, SHELL and HOME
variables as per crontab(4) entry varaiables, these are the only ones
that change the way cron behaves.  All others can be achieved via
having the entry set the variable (SHELL is the weakest of the three to
change as it only saves on exec).

HOME solves the problems associated with NFS and cronjobs where a users
home directory is not available when the entry runs (as in the case with
secure NFS).

TZ obviously sets the time zone when the entry is valid. Allowing jobs
to run in any time zone.

The variables continue to effect all entries below them until new
entries are listed in the file. Entries would run with a HOME directory
set to the one listed and at times that are correct according to the TZ
value and with a shell specified by SHELL.

Setting any other variable results in an error when you try and save
the crontab file.

Use of this facility is controlled by an entry in the already existing
/etc/default/cron [ the project team is aware that ideally this and the
existing cron(1M) use of this file should migrate to SMF properties but
that is not this case ]. If there is an entry of the form:

	ALLOW_EXTENSIONS=YES

in the file then the entries are allowed otherwise cron and crontab
behave as it do now and crontab will not let you add the lines and cron
will not process them, instead treating them as errors.

The one problem area would be if an Admin removed the entry from
/etc/default/cron while there were crontab files that contained those
entries.  When cron was restarted all the lines would be reported as
in error and potentially cron jobs could run at the wrong times with
the wrong shell and wrong HOME directory.

OpenSolaris distributions would decide whether they wish to allow the
extensions or not by default and provide an /etc/default/cron with
ALLOW_EXTENSIONS set to YES or NO depending on that decision.  This
case declares the default for the Solaris distribution to be YES.

All the functionality defined in this case is exported as Committed interfaces
with a release binding of patch.

Updated man pages are in the materials directory.

6. Resources and Schedule
    6.4. Steering Committee requested information
   	6.4.1. Consolidation C-team Name:
		ON
    6.5. ARC review type: FastTrack
    6.6. ARC Exposure: open