Managing cron and similar E-Mails from headless systems
heller at deepsoft.com
Fri Feb 17 18:06:13 UTC 2017
At Fri, 17 Feb 2017 11:00:16 -0500 "Ubuntu user technical support, not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:
> On Friday 17 February 2017 06:14:01 Chris Green wrote:
> > I have several headless systems doing useful work around the place:-
> > A Raspberry Pi providing local DNS and DHCP
> > A Beaglebone Black on our boat monitoring temperatures and
> > batteries
> > An old desktop doing backups in the garage
> > etc.
> > Most of these have one or more cron jobs running periodic rsync
> > backups, copying data, etc. If the cron job has an error then it
> > sends E-Mail to the owner of the job ('chris' in most cases, might be
> > root in a couple).
> > It's (moderately) easy to set up an MTA and /etc/aliases so that the
> > messages are sent to my normal E-Mail. However I can't come up with a
> > straightforward way of indicating where the messsage is *from*.
> > You can't just invent a domain name for the headless system because
> > that gets the E-Mail rejected by intermediate systems that try and
> > look up the sender host name. Cron doesn't seem to have any mechanism
> > for setting the sender's name, cron errors just come from 'root@'.
> > Can anyone suggest a neat way of handling this so that I know where
> > the errors are coming from?
> > --
> > Chris Green
> A hosts file based home network should suffice to fix that. I did have it
The OP is already running a DNS server, so he really does not need to bother
with a hosts file.
I expect the problem is that he is sending these E-Mails off the local LAN to
some E-Mail address "in the cloud" and spam filters are going to reject them
because the From: header will be wonky (like root at rpi3.my.local.domain).
What he needs to do is set up a "gateway" system -- one of the machines on the
LAN needs to be set up as an outbound SMTP server for the LAN and needs to
Masqurade the addresses (eg rewrite the From: header) to something sane, like
his personal E-Mail address and add an X-Orig-From: headr line with the
original From: header. Or else set up a procmail recipe (on of the machines on
the LAN) that forwards the messages from his personal address.
> setup to do that from 3 of the now 5 machines here, but the inability to
> separate the messages into important turned the whole thing into spam
> for me. Set your resolv.conf to include the commands:
> "nameserver local.address.of.router"
> "order hosts,dns"
> So it will look at /etc/hosts first, failing to find a match there it
> sends it to the router, which forwards it to your ISP's dns.
> 1. Set the hostname and domain name of your machines so they know who
> they are.
> 2. run the same hosts file on all machines, which lists the local ip,
> names, and aliases of the whole local network, 7 lines here plus the
> obligatory localhost stuff, does it nicely. Then on the client
> machines, I just set the MailTo: gene at coyote, and it magically appears
> in my /var/spool/mail/gene queue. That in turn triggers a watcher script
> to send kmail a getmail message over whatever message bus your system
> uses, dbus here ATM, to go get the mail.
> But unless you can make procmail (I use a fetchmail->procmail processing
> chain here) send the unimportant stuff to /dev/null, you'll likely tear
> it back down in a week or 2. You don't need to know, when logging into
> one of the other machines, everytime you fat fingered the password. With
> my short fat fingers, and 82 years of arthritis accumulated, very easily
> Cheers, Gene Heskett
Robert Heller -- 978-544-6933
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