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error writing to filter -- Who are you?

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  • email builder
    Hi, Been a while since I had to look at our mail system (a tribute to postfix/courier/spamassassin/sasl/related software), but when upgrading all our software
    Message 1 of 3 , Aug 3, 2008
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      Hi,

      Been a while since I had to look at our mail system (a tribute to postfix/courier/spamassassin/sasl/related software), but when upgrading all our software recently, I ran into a couple issues, the 2nd one being particularly confounding (and not much turns up via a Google search, thus I thought I would post this in case someone else has the same problem(s)). Postfix isn't a culprit in any of this, but just wanted to post my saga here in case anyone else comes looking for similar issues.

      We upgraded to Fedora Core 9. We have a virtual users setup with our users in MySQL and no local users.

      First, I was unable to get any SMTP connections to work - (sasl) auth was failing. We use the pam-mysql package so that sasl can auth against our database. I eventually tracked this down to some odd symlinks -- I had edited /etd/pam.d/smtp as I always do without realizing that it was a symlink to /etc/alternatives/mta-pam, which itself is a symlink to /etc/alternatives/smtp.sendmail. First mistake. Second mistake was I was in too much of a hurry to stop and ask "what's this symlink 'alternatives' crap?" I just mucked with the symlinks until it worked.

      Much later, I started to see that our autoresponder was not working. I was seeing some errors I'd never seen before:

      Aug 3 10:02:19 mail postfix/pipe[6291]: 7BA7D38F21C: to=<someone@...>, relay=maildrop, delay=0.92, delays=0.06/0.01/0/0.85, dsn=5.3.0, status=bounced (internal software error. Command output: sh: /usr/bin/spamc: No such file or directory maildrop: error writing to filter. Who are you? )

      Huh? Well, after a while being stupid, I managed to realize I have to look above that for any other errors in the mail log. I found:

      Aug 3 10:02:18 mail sendmail[6297]: m192B5Z9926297: SYSERR(UID5021): Who are you?
      Aug 3 10:02:18 mail sendmail[6297]: m192B5Z9926297: Authentication-Warning: mail.example.com: Unknown UID 5021 set sender to <> using -f

      OK, so the problem is that the MTA is not understanding who the message is from, when it gets reinjected from spam checks. The 5021 uid is a virtual uid, not a system one. Why is the MTA looking for a *system* uid? Hmm, looks like it's the real sendmail and not postfix masquerading as postfix. I don't know how to tell the difference, so I Googled around a lot, but didn't find much until I see once again that the sendmail binary is actually a symlink. Ah, here we go again with this alternatives crap:

      /usr/sbin/sendmail --> /etc/alternatives/mta --> /usr/sbin/sendmail.sendmail

      First I just changed that last symlink to point to /usr/sbin/sendmail.postfix, but when starting postfix I get:

      postfix/postfix-script: warning: /usr/lib/sendmail and /usr/sbin/sendmail differ
      postfix/postfix-script: warning: Replace one by a symbolic link to the other
      postfix/postfix-script: starting the Postfix mail system

      More Googling - not many results. OK, OK, I'll try to understand what this all means. Google still didn't give me much, but I see it's some dumb package switcher.

      man alternatives
      http://dailypackage.fedorabook.com/index.php?/archives/6-Wednesday-Why-The-Alternatives-System.html
      http://linux.derkeiler.com/Mailing-Lists/RedHat/2004-08/0256.html

      That's about all I found, but it's enough. Personally, this seems ridiculous to me, but oh well. I changed all the symlinks for both the mta stuff and the pam stuff back to what they were in the first place (and edited the correct pam.d/smtp.postfix file) and did it the "Right Way":

      alternatives --set mta /usr/sbin/sendmail.postfix

      Verify with:

      alternatives --display mta

      Yeesh. Now it works.


      HTH
    • Brian Evans - Postfix List
      ... A much easier way to solve this and prevent errors in the future is rpm -e sendmail . The sendmail package will *not* remove Postfix s sendmail client.
      Message 2 of 3 , Aug 4, 2008
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        email builder wrote:
        > /usr/sbin/sendmail --> /etc/alternatives/mta --> /usr/sbin/sendmail.sendmail
        >
        > First I just changed that last symlink to point to /usr/sbin/sendmail.postfix, but when starting postfix I get:
        >
        > postfix/postfix-script: warning: /usr/lib/sendmail and /usr/sbin/sendmail differ
        > postfix/postfix-script: warning: Replace one by a symbolic link to the other
        > postfix/postfix-script: starting the Postfix mail system
        >
        > More Googling - not many results. OK, OK, I'll try to understand what this all means. Google still didn't give me much, but I see it's some dumb package switcher.
        >
        > man alternatives
        > http://dailypackage.fedorabook.com/index.php?/archives/6-Wednesday-Why-The-Alternatives-System.html
        > http://linux.derkeiler.com/Mailing-Lists/RedHat/2004-08/0256.html
        >
        > That's about all I found, but it's enough. Personally, this seems ridiculous to me, but oh well. I changed all the symlinks for both the mta stuff and the pam stuff back to what they were in the first place (and edited the correct pam.d/smtp.postfix file) and did it the "Right Way":
        >
        > alternatives --set mta /usr/sbin/sendmail.postfix
        >
        A much easier way to solve this and prevent errors in the future is 'rpm
        -e sendmail'.

        The sendmail package will *not* remove Postfix's sendmail client.

        Brian
      • email builder
        ... I suppose removing sendmail would also do the trick (I use yum, however, but same thing applies). It s a few less keystrokes, but in the end it s one CLI
        Message 3 of 3 , Aug 4, 2008
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          Brian Evans - Postfix List <grknight <at> scent-team.com> writes:

          > > alternatives --set mta /usr/sbin/sendmail.postfix
          >
          > A much easier way to solve this and prevent errors in the future is 'rpm
          > -e sendmail'.
          >
          > The sendmail package will *not* remove Postfix's sendmail client.

          I suppose removing sendmail would also do the trick (I use yum, however, but
          same thing applies). It's a few less keystrokes, but in the end it's one CLI
          command either way.
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