xref: /freebsd-10.1-release/usr.sbin/cron/doc/CONVERSION

$FreeBSD$

Conversion of BSD 4.[23] crontab files:

Edit your current crontab (/usr/lib/crontab) into little pieces, with each
users' commands in a different file.  This is different on 4.2 and 4.3,
but I'll get to that below.  The biggest feature of this cron is that you
can move 'news' and 'uucp' cron commands into files owned and maintainable
by those two users.  You also get to rip all the fancy 'su' footwork out
of the cron commands.  On 4.3, there's no need for the 'su' stuff since the
user name appears on each command -- but I'd still rather have separate
crontabs with separate environments and so on.

Leave the original /usr/lib/crontab!  This cron doesn't use it, so you may
as well keep it around for a while in case something goes wakko with this
fancy version.

Most commands in most crontabs are run by root, have to run by root, and
should continue to be run by root.  They still have to be in their own file;
I recommend /etc/crontab.src or /usr/adm/crontab.src.

'uucp's commands need their own file; how about /usr/lib/uucp/crontab.src?
'news' also, perhaps in /usr/lib/news/crontab.src...

I say `how about' and `perhaps' because it really doesn't matter to anyone
(except you) where you put the crontab source files.  The `crontab' command
COPIES them into a protected directory (CRONDIR/SPOOL_DIR in cron.h), named
after the user whose crontab it is.  If you want to examine, replace, or
delete a crontab, the `crontab' command does all of those things.  The
various `crontab.src' (my suggested name for them) files are just source
files---they have to be copied to SPOOLDIR using `crontab' before they'll be
executed.

On 4.2, your crontab might have a few lines like this:

	5 * * * *   su uucp < /usr/lib/uucp/uudemon.hr
	10 4 * * *  su uucp < /usr/lib/uucp/uudemon.day
	15 5 * * 0  su uucp < /usr/lib/uucp/uudemon.wk

...or like this:

	5 * * * *   echo /usr/lib/uucp/uudemon.hr | su uucp
	10 4 * * *  echo /usr/lib/uucp/uudemon.day | su uucp
	15 5 * * 0  echo /usr/lib/uucp/uudemon.wk | su uucp

On 4.3, they'd look a little bit better, but not much:

	5 * * * *   uucp  /usr/lib/uucp/uudemon.hr
	10 4 * * *  uucp  /usr/lib/uucp/uudemon.day
	15 5 * * 0  uucp  /usr/lib/uucp/uudemon.wk

For this cron, you'd create /usr/lib/uucp/crontab.src (or wherever you want
to keep uucp's commands) which would look like this:

	# /usr/lib/uucp/crontab.src - uucp's crontab
	#
	PATH=/usr/lib/uucp:/bin:/usr/bin
	SHELL=/bin/sh
	HOME=/usr/lib/uucp
	#
	5 * * * *   uudemon.hr
	10 4 * * *  uudemon.day
	15 5 * * 0  uudemon.wk

The application to the `news' cron commands (if any) is left for you to
figure out.  Likewise if there are any other cruddy-looking 'su' commands in
your crontab commands, you don't need them anymore: just find a good place
to put the `crontab.src' (or whatever you want to call it) file for that
user, put the cron commands into it, and install it using the `crontab'
command (probably with "-u USERNAME", but see the man page).

If you run a 4.2-derived cron, you could of course just install your current
crontab in toto as root's crontab.  It would work exactly the way your
current one does, barring the extra steps in installing or changing it.
There would still be advantages to this cron, mostly that you get mail if
there is any output from your cron commands.

One note about getting mail from cron: you will probably find, after you
install this version of cron, that your cron commands are generating a lot
of irritating output.  The work-around for this is to redirect all EXPECTED
output to a per-execution log file, which you can examine if you want to
see the output from the "last time" a command was executed; if you get any
UNEXPECTED output, it will be mailed to you.  This takes a while to get
right, but it's amazingly convenient.  Trust me.