How to check, if there is an update for mailcow

Let us assume that mailcow (dockerized) is installed in the directory /opt/mailcow-dockerized, then the script below checks, if there is an update and sends an email to the hostmaster:

#!/bin/bash
set -o nounset
set -o errexit

cd /opt/mailcow-dockerized && ./update.sh --check > /dev/null
exit_code=$?

[ $exit_code -eq 0 ] && echo -e "Subject:MAILCOW: Update available \n\n Update your mailcow instance please!\n" | sendmail hostmaster@your-domain.com
exit 0

The scrip can be run as cron.

MySQL: backup databases in separate files and zip it to STDOUT

It’s not very comfortable to restore one database, if you have just one big fat backup file, which contains all databases.

My solution is the bash script above does the following steps:

1. It crreates one dump file for each database.
2. It packs all dump files in one zipfile
3. and sends it to STDOUT.

Step 3 is very helpful e.g. for using this script with backup software like rsnapshot.

## Dumps every database to a single file, all dump files will be zipped and redirected to the stdout.
## Usage: backup-db.sh > databases.zip
##
#! /bin/bash
set -o nounset
set -o errexit

trap 'rm -rf "$BACKUP_DIR"' EXIT
BACKUP_DIR=$(mktemp -d)
MYSQL=/usr/bin/mysql
MYSQLDUMP=/usr/bin/mysqldump

databases=`$MYSQL --defaults-extra-file=/etc/mysql/credentials.cnf --default-character-set=utf8mb4 -e "SHOW DATABASES;" \
        | grep -Ev "(Database|information_schema|performance_schema)"`
for db in $databases; do
  $MYSQLDUMP --defaults-extra-file=/etc/mysql/credentials.cnf --default-character-set=utf8mb4 --force --opt --databases $db \
        > "$BACKUP_DIR/$db.sql"
done
zip -rjq - "$BACKUP_DIR"
exit 0

The corresponding gist at github: https://gist.github.com/th-schwarz/38dd9fa1cdba05506f642a633095bad7

dnsmasq and logrotate on ubuntu 20.04

I had same issues with dnsmasq and logrotate on ubuntu 20.04. Here is my solution:

In /etc/dnsmasq.conf the following entry is required:

log-facility=/var/log/dnsmasq/dnsmasq.log

Create /etc/logrotate.d/dnsmasq with the following content:

/var/log/dnsmasq/dnsmasq.log {
   size 100M
   weekly
   rotate 7
   compress
   missingok
   notifempty
   postrotate
      service dnsmasq restart
   endscript
}

The important thing was the restart of dnsmasq!

How to check the expiration date of a ssl certificate?

To check a certificate of an host:

openssl s_client -servername your.domain -connect your.domain:443 2>&- | openssl x509 -enddate -noout | sed 's/^notAfter=//g'

To check a certificate file:

openssl x509 -noout -enddate -in your.crt | sed 's/^notAfter=//g'

 

Apache failed on system boot, when binding to an additional IP

Starting point:

My system (Ubuntu 18.04.1) is a VPS running on KVM. The network with some additional IPs is configured with Netplan.

 

Problem:

The Apache server is running on an additional IP. If the VPS reboots, the apache didn’t start because, it couldn’t be bind on an aditional IP. A log entry like the following can be found:
apachectl[631]: (99)Cannot assign requested address: AH00072: make_sock: could not bind to address [xxxxxxxx]:80

But if you restart Apache after the reboot, it runs as expected!
Strange, isn’t it?

 

Solution:

Ok, I couldn’t find the exact reason of this reason. But I think, there is a strange timing issue on reboot. The network isn’t completely up before Apache is starting.

To solve the problem, just edited the section ‘Unit’ in the file /lib/systemd/system/apache2.service and replace

After=network.target remote-fs.target nss-lookup.target

with

Requires=network-online.target
After=network-online.target remote-fs.target nss-lookup.target

That’s it!

More information about the network-target can be found her: https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/