dependency (S-nail) improperly configured

[Matt Klyn]

Ubuntu 20.04:

If there is no mail/mailx command, then installing apcupsd will require to install s-nail, probably as a replacement of the former 'heirloom-mailx'. S-nail is a replacement for mail/mailx, with the same syntax. Installing s-nail only provides s-nail command though, and not the mail/mailx commands (as heirloom-mailx used to make) expected by apcupsd.

Steps:

1. Bug/proof: install apcupsd, unplug and replug APC. It does not send any email to root from root.

2. Fix: Of course you can always hack the and add some email commands in /etc/apcupsd/apccontrol but this is not correcting the bug at its root. To correct issue properly, simply issue

* sudo ln -s /usr/bin/s-nail /etc/alternatives/mailx (optionnal)
* sudo ln -s /etc/alternatives/mailx /usr/bin/mailx (optionnal)

* sudo ln -s /usr/bin/s-nail /etc/alternatives/mail
* sudo ln -s /etc/alternatives/mail /usr/bin/mail

try again to unplug and plug back UPS. You now get email messages for each events as it should w//o changing apccontrol file.

In clear, s-nail dependency is useless, unless we add the 2 simlinks. Only mail, not mailx is really needed (i guess this is because of the mail command in /etc/default/apcupsd) , but it's nice to have both mail/mailx anyway if installing s-nail. I'm not sure if this is a pure apcupsd issue, or s-nail issue. Those 2 links to mail and mailx are not done by s-nail itself, probably for a reason, so I suggest this is more a apcupsd install/config issue.

Regards -- mk