sl: properly install changed certificate and restart apache on changes

Pin Selfoss version to an actual release

Generate 2048 DH group and add it to Postfix

update openvpn server config

Change default network buffer size
Should increase tcp tunnel speed for openvpn < 2.3.9
https://community.openvpn.net/openvpn/ticket/461

Configure logrotate permissions for selfoss

Remove reference to Google's DNS servers

Per discussion on #429 (after the merge). This project is about encouraging users to run services themselves and not rely on for-profit corporations such as Google.

Add SSL stapling cache for distributions with Apache 2.4+

Fixes #406

Closes #429

add additional comment about `tun-mtu` parameter in openvpn config template

- google dns setting for client
- verb level
- mtu
- TLS settings

Notes about security: https://blog.g3rt.nl/openvpn-security-tips.html
Check privacy: http://witch.valdikss.org.ru/

change auth to internal_hashed

Use common_timezone and fix idempotence

Add some info on DMARC

Thanks-to: 8e693b3db3

I ran a check on http://mail-tester.com and found out I was missing a header to be set for DMARC. SInce I missed it, maybe someone else missed it as well, so maybe it could go into the README.

because why the fuck not?

Fix typo in tarsnap.yml

Resolves #388.

Resolves #400.

Resolves #402.

Resolves #410.

Couple issues with OpenDMARC on Debian 7:

Added whois for fail2ban report

Use lmtp instead of lda for delivery.

These already set in defaults.yml

Fix apache SSL config for wheezy

 * fix mail_db_opendmarc_username/mail_db_opendmarc_password variable
   not found.
 * python-mysqldb package is required. Add it to opendmarc task.

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