Date: Sat, 24 Oct 2009 10:16:36 +0100 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: Kelly Martin <kellymartin@gmail.com> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: changing cron's From: address in emails Message-ID: <4AE2C5F4.20109@infracaninophile.co.uk> In-Reply-To: <1338880b0910240008h5d5e7846q8ccf184728d9e036@mail.gmail.com> References: <1338880b0910240008h5d5e7846q8ccf184728d9e036@mail.gmail.com>
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Kelly Martin wrote:
> Greetings, here's a simple question for the FreeBSD gurus out there. I
> have several servers running cron scripts daily for me, and they all
> send me e-mail with their output. Regardless of which server it is,
> each of these e-mails have the From: address looking exactly the same.
> They all say they are from the "Cron Daemon". Fine, but I'd like to
> know more clearly which server the cron output is from.
>=20
> How can I change the From: address of these emails to "Myserver Cron
> Daemon" instead? I know cron runs as the user, so it's not immediately
> obvious to me how to change the From: field. Already the subject line
> says something like "Cron <root@Myserver> ..." but this doesn't stand
> out enough for my tired eyes.
Hmmm... that's actually quite tricky. There's no facility within
cron(8) for changing the address it sends /from/, and as the bit you
want to change is technically a comment on the From: line, and not
the actual sender address (the bit in the <angle brackets>) all the
address rewriting-fu in sendmail won't really help. Besides, root@...
is listed as a member of the 'Exposed User' class: that is, addresses
that should be exempt from address rewriting, so you'ld also have to
modify that.
Do you control the mail server where you read your e-mail? Can you use
eg. procmail(1) as a delivery agent? You should be able to match e-mails=
from Cron and rewrite headers, or deliver cron e-mails into per-machine
mailboxes. Something like this:
:0 h
* From:.*Cron <root@\/[^\.]+
$MATCH
The other alternative is to re-write the cron scripts to send e-mail
themselves, rather than relying on cron(8) to capture their stdout/stderr=
and e-mail it for you. Here's a handy shell programming trick that can
make that easier. Somewhere near the top of the script, you can add
something like this:
exec 2>&1 | /usr/sbin/sendmail -oi -t
echo "From: Sender Name <sender@add.ress>
echo "To: <recipient@some.where>
echo "Subject: e-mail from cron job"
echo ""
Then everything you print out in the script will be captured as the body
of the e-mail and sent to the specified recipient. You might get some=20
warnings about forgery in the mail headers if the userid the script runs
as is not the same as the 'From:' address.
Cheers,
Matthew
--=20
Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard
Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate
Kent, CT11 9PW
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