billydavies
Posts: 2
Joined: Wed Mar 20, 2013 11:31 am

rsyslogd was HUPed

Wed Mar 20, 2013 11:46 am

Hello,
Anyone know what the following means?

Mar 20 06:25:05 raspberrypi rsyslogd: [origin software="rsyslogd" swVersion="5.8.11" x-pid="1616" x-info="http://www.rsyslog.com"] rsyslogd was HUPed

... the message (in /var/log/messages) appears every day at the same time. Obviously, the SD card can handle one message per day for a very long time. I'm more curious though, as the rsyslog.com website looks a little 'out of context' (so to speak) for the RPi and although 'professional support is just one click away' (as they say) I wondered if anyone here has any ideas?

Thanks

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rurwin
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Re: rsyslogd was HUPed

Wed Mar 20, 2013 12:46 pm

HUP is a signal, which is Unix-speak for something that interrupts a program. Other signals are created by pressing Ctrl-C or when the program tries to divide by zero. This particular signal is generated when a modem connection drops -- it's called Hang-UP.

So far, so confusing.

What that doesn't explain, is that many Linux programs use the HUP signal as an instruction to re-read their configuration files. A program like rsyslogd is running all the time, and it probably only reads its configuration files when it starts. If the user makes some changes, rsyslogd wont notice and will continue doing things the old way. So the user can send a HUP signal to the rsyslogd process to tell it the configuration files have changed and it should read them again. Just to be sure, it seems something sends rsyslogd a HUP signal every day, in case the user changes something and forgets to send the signal.

You can send signals with the also confusingly named "kill" command. See its man page for details.

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jojopi
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Re: rsyslogd was HUPed

Wed Mar 20, 2013 1:11 pm

The signal is sent by logrotate (see "postrotate" in /etc/logrotate.d/rsyslog). It is to tell rsyslogd to stop writing to the old log files that have now been renamed.

billydavies
Posts: 2
Joined: Wed Mar 20, 2013 11:31 am

Re: rsyslogd was HUPed

Wed Mar 20, 2013 1:23 pm

Thanks jojopi. Yes, the time of rotation in /var/log/ (for the logs listed in /etc/logrotate.d/rsyslog) is the same time as the 'rsyslogd was HUPed' message. This is the only message that appears in /var/log/messages (the RPi runs 24/7 monitoring room temperatures) and seems unnecessary. However, one line per day will not harm anything.
Thanks for your help.

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