[gentoo-user] crontab questions

[gentoo-user] crontab questions

[Grant]

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Is there a way to remove "Cron <root@hostname>" from the subject line of
crontab mail without piping each cron job to 'mail'?

I set 'usermod -c hostname root' on each of my systems so that the From:
line displays "hostname" for crontab mail.  This works on each system
except the mail server itself which still shows "Cron Daemon".  Can crontab
mail from the mail server be made to display From: "hostname" like the
other systems?

I'm not completely clear on how cronbase works.  Can this crontab be
integrated into the system crontab via cronbase or should it be run as a
separate user crontab for root?

0 4 * * * layman -NS && eix-sync -n && eix-remote update -n
15 4 * * * emerge -pvDuN world
20 4 * * * eclean -C distfiles
30 4 * * * eclean -C packages
40 4 * * * eix-test-obsolete
45 4 * * * revdep-rebuild -ip

- Grant

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Re: [gentoo-user] crontab questions

[Michael Orlitzky]

On 12/11/2012 04:15 PM, Grant wrote:
> Is there a way to remove "Cron <root@hostname>" from the subject line of
> crontab mail without piping each cron job to 'mail'?
> 
> I set 'usermod -c hostname root' on each of my systems so that the From:
> line displays "hostname" for crontab mail.  This works on each system
> except the mail server itself which still shows "Cron Daemon".  Can
> crontab mail from the mail server be made to display From: "hostname"
> like the other systems?
> 
> I'm not completely clear on how cronbase works.  Can this crontab be
> integrated into the system crontab via cronbase or should it be run as a
> separate user crontab for root?
> 
> 0 4 * * * layman -NS && eix-sync -n && eix-remote update -n
> 15 4 * * * emerge -pvDuN world
> 20 4 * * * eclean -C distfiles
> 30 4 * * * eclean -C packages
> 40 4 * * * eix-test-obsolete
> 45 4 * * * revdep-rebuild -ip
> 

If your goal is to run these each one after the other, you can simply
stick a shell script in /etc/cron.daily that executes them in order.

The default crontab runs any executable files in,

  * /etc/cron.daily
  * /etc/cron.hourly
  * /etc/cron.monthly
  * /etc/cron.weekly

at roughly the time specified in /etc/crontab. If any of those
directories contain scripts, they're run in "alphabetical" order, i.e.
how `ls` would sort them.

To fix the Subject/From headers, try,

  http://www.postfix.org/header_checks.5.html

I've never had to use them myself, but I think the REPLACE action will
do what you want. The alternative is to replace the sendmail binary with
something that executes e.g.,

  sed -e 's/Subject: Cron <[^>]> /Subject: /g' | /the/actual/sendmail

Both feel a little dirty, but the header checks are less likely to break
something assuming that they will work on a client-provided From header.

Re: [gentoo-user] crontab questions

[Grant]

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> > Is there a way to remove "Cron <root@hostname>" from the subject line of
> > crontab mail without piping each cron job to 'mail'?
> >
> > I set 'usermod -c hostname root' on each of my systems so that the From:
> > line displays "hostname" for crontab mail.  This works on each system
> > except the mail server itself which still shows "Cron Daemon".  Can
> > crontab mail from the mail server be made to display From: "hostname"
> > like the other systems?
> >
> > I'm not completely clear on how cronbase works.  Can this crontab be
> > integrated into the system crontab via cronbase or should it be run as a
> > separate user crontab for root?
> >
> > 0 4 * * * layman -NS && eix-sync -n && eix-remote update -n
> > 15 4 * * * emerge -pvDuN world
> > 20 4 * * * eclean -C distfiles
> > 30 4 * * * eclean -C packages
> > 40 4 * * * eix-test-obsolete
> > 45 4 * * * revdep-rebuild -ip
> >
>
> If your goal is to run these each one after the other, you can simply
> stick a shell script in /etc/cron.daily that executes them in order.
>
> The default crontab runs any executable files in,
>
>   * /etc/cron.daily
>   * /etc/cron.hourly
>   * /etc/cron.monthly
>   * /etc/cron.weekly
>
> at roughly the time specified in /etc/crontab. If any of those
> directories contain scripts, they're run in "alphabetical" order, i.e.
> how `ls` would sort them.

Thanks Michael.  I'd like to have more control over when the commands are
run.  Maybe the system crontab (cronbase) should be used when that control
isn't necessary or to allow programs to add stuff to a crontab, and a user
crontab should be used when more control is necessary?

> To fix the Subject/From headers, try,
>
>   http://www.postfix.org/header_checks.5.html
>
> I've never had to use them myself, but I think the REPLACE action will
> do what you want. The alternative is to replace the sendmail binary with
> something that executes e.g.,
>
>   sed -e 's/Subject: Cron <[^>]> /Subject: /g' | /the/actual/sendmail
>
> Both feel a little dirty, but the header checks are less likely to break
> something assuming that they will work on a client-provided From header.

I think it's better for me to pipe the commands to mailx.  I get mail if I
run this on the command line

emerge -pvDuN world | /usr/bin/mail -s "subject" -a "From: from"
my@email.com

But I don't get any mail when it runs in the crontab.  Do you know why
that's happening?  I do get mail from 'emerge -pvDuN world' run in the
crontab without piping it to mail.

- Grant

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Re: [gentoo-user] crontab questions

[Michael Orlitzky]

On 12/12/2012 05:09 PM, Grant wrote:
>>
>> at roughly the time specified in /etc/crontab. If any of those
>> directories contain scripts, they're run in "alphabetical" order, i.e.
>> how `ls` would sort them.
> 
> Thanks Michael.  I'd like to have more control over when the commands
> are run.  Maybe the system crontab (cronbase) should be used when that
> control isn't necessary or to allow programs to add stuff to a crontab,
> and a user crontab should be used when more control is necessary?
> 

I personally like the idea of the cron.{daily,weekly,...}, but the
implementation is a little goofy. On our mail server, I've added an
additional directory called cron.bihourly to update virus/spam
signatures every two hours. The simplest way to accomplish this is to add,

  # Run every two hours
  0  */2 * * *  root   find -L /etc/cron.bihourly -type f -executable \
                            -execdir '{}' \;

in the global /etc/crontab. I'm sure this is horribly deficient
according to whoever implemented the run-crons stuff, but for me the
additional clarity is worth it.

You can of course add anything else you like in the global/user
crontabs, and they'll work normally.

But be careful: do you really want `emerge -puDN` to run 15 minutes
after you start an `eix-sync`? Or do you just want it to run when
`eix-sync` is done? If it's the latter, you don't want to schedule it 15
minutes later -- you could hit a slow mirror and still be updating when
the `emerge` kicks off. In that case it's better to put all of the
commands in one script, and schedule that when you want. That way the
commands occur in sequence, and you can bail out if something fails.


>> To fix the Subject/From headers, try,
>>
>>   http://www.postfix.org/header_checks.5.html
>>
>> I've never had to use them myself, but I think the REPLACE action will
>> do what you want. The alternative is to replace the sendmail binary with
>> something that executes e.g.,
>>
>>   sed -e 's/Subject: Cron <[^>]> /Subject: /g' | /the/actual/sendmail
>>
>> Both feel a little dirty, but the header checks are less likely to break
>> something assuming that they will work on a client-provided From header.
> 
> I think it's better for me to pipe the commands to mailx.  I get mail if
> I run this on the command line
> 
> emerge -pvDuN world | /usr/bin/mail -s "subject" -a "From: from"
> my@email.com <mailto:my@email.com>
> 
> But I don't get any mail when it runs in the crontab.  Do you know why
> that's happening?  I do get mail from 'emerge -pvDuN world' run in the
> crontab without piping it to mail.

I'm not sure. I do the same thing, though, albeit with a temporary file
(and it works). Maybe try `echo`ing the output to a file? This script
emails me the current iptables to make sure fail2ban hasn't gone berserk:

  #!/bin/bash

  # Send the current iptables -L -n output to the postmaster.

  TMPFILE=/tmp/iptables-state.log
  MAILADDR="postmaster@example.com"

  echo "To: $MAILADDR" > $TMPFILE
  echo "From: root@mx1.example.com" >> $TMPFILE
  echo "Subject: mx1 iptables state" >> $TMPFILE

  iptables -L -n >> $TMPFILE

  sendmail -f root@mx1.example.com \
           $MAILADDR              \
           < $TMPFILE
	
  rm $TMPFILE

It's not very fancy but it does work. If a temp file works for you, it
might help you narrow down the problem.

Re: [gentoo-user] crontab questions

[Grant]

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> > Thanks Michael.  I'd like to have more control over when the commands
> > are run.  Maybe the system crontab (cronbase) should be used when that
> > control isn't necessary or to allow programs to add stuff to a crontab,
> > and a user crontab should be used when more control is necessary?
> >
>
> I personally like the idea of the cron.{daily,weekly,...}, but the
> implementation is a little goofy. On our mail server, I've added an
> additional directory called cron.bihourly to update virus/spam
> signatures every two hours. The simplest way to accomplish this is to add,
>
>   # Run every two hours
>   0  */2 * * *  root   find -L /etc/cron.bihourly -type f -executable \
>                             -execdir '{}' \;
>
> in the global /etc/crontab. I'm sure this is horribly deficient
> according to whoever implemented the run-crons stuff, but for me the
> additional clarity is worth it.
>
> You can of course add anything else you like in the global/user
> crontabs, and they'll work normally.

OK, I've moved all of my user crontabs (including root) to /etc/crontab.

> But be careful: do you really want `emerge -puDN` to run 15 minutes
> after you start an `eix-sync`? Or do you just want it to run when
> `eix-sync` is done? If it's the latter, you don't want to schedule it 15
> minutes later -- you could hit a slow mirror and still be updating when
> the `emerge` kicks off. In that case it's better to put all of the
> commands in one script, and schedule that when you want. That way the
> commands occur in sequence, and you can bail out if something fails.

Done.

> > I think it's better for me to pipe the commands to mailx.  I get mail if
> > I run this on the command line
> >
> > emerge -pvDuN world | /usr/bin/mail -s "subject" -a "From: from"
> > my@email.com <mailto:my@email.com>
> >
> > But I don't get any mail when it runs in the crontab.  Do you know why
> > that's happening?  I do get mail from 'emerge -pvDuN world' run in the
> > crontab without piping it to mail.

I got it working in /etc/crontab.  Should I file a bug for
http://www.gentoo.org/doc/en/cron-guide.xml to mention that vixie-cron must
be restarted when making changes to /etc/crontab?  It says:

"Note that only Vixie-cron schedules jobs in /etc/crontab automatically."

> I'm not sure. I do the same thing, though, albeit with a temporary file
> (and it works). Maybe try `echo`ing the output to a file? This script
> emails me the current iptables to make sure fail2ban hasn't gone berserk:
>
>   #!/bin/bash
>
>   # Send the current iptables -L -n output to the postmaster.
>
>   TMPFILE=/tmp/iptables-state.log
>   MAILADDR="postmaster@example.com"
>
>   echo "To: $MAILADDR" > $TMPFILE
>   echo "From: root@mx1.example.com" >> $TMPFILE
>   echo "Subject: mx1 iptables state" >> $TMPFILE
>
>   iptables -L -n >> $TMPFILE
>
>   sendmail -f root@mx1.example.com \
>            $MAILADDR              \
>            < $TMPFILE
>
>   rm $TMPFILE
>
> It's not very fancy but it does work. If a temp file works for you, it
> might help you narrow down the problem.

Wouldn't you rather use a one-liner like this?

iptables -L -n | mail -s "mx1 iptables state" -a "From: root@mx1.example.com"
postmaster@example.com

- Grant

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Re: [gentoo-user] crontab questions

[Michael Orlitzky]

On 12/14/2012 09:36 PM, Grant wrote:
> 
> I got it working in /etc/crontab.  Should I file a bug for
> http://www.gentoo.org/doc/en/cron-guide.xml to mention that vixie-cron
> must be restarted when making changes to /etc/crontab?  It says:
> 
> "Note that only Vixie-cron schedules jobs in /etc/crontab automatically."
> 

You shouldn't have to restart vixie-cron, I think it just scans
/etc/crontab every so often.


> Wouldn't you rather use a one-liner like this?
> 
> iptables -L -n | mail -s "mx1 iptables state" -a "From:
> root@mx1.example.com <mailto:root@mx1.example.com>"
> postmaster@example.com <mailto:postmaster@example.com>
> 

Even the simple stuff I like to keep in a separate shell script. They're
all under version control so that if one server blows up, all I have to
do is checkout the git repo and hit `make` on another box and everything
will more-or-less work once I emerge @world.

I could avoid using a temp file that way, but it ain't broke so I'm not
going to fix it.