Security   Security – Create self signed SAN certificate with OpenSSL



This post explains how to generate self signed certificates with SAN – Subject Alternative Names using openssl. It is a common but not very funny task, only a minute is needed when using this method.

The example below generates a certificate with two SubAltNames: mydomain.com and www.mydomain.com

Create openssl configuration file

Create configuration file for openssh (In a Linux … Read more

Icinga icon   Icinga – Cannot login to Grafana. Forgot admin password



It is not the first time my Icinga suddenlty, stops showing the grafana graphs.
Icinga when cannot show Grafana graphs

Problem

If trying to log to Grafana, admin password is not accepted. I am pretty sure i have not changed the password but I am unable to login to Grafana.
Invalid username or password when login to Grafana
And even worse, given that I still have not configured Grafana SMTP section / admin … Read more

Icinga icon   Icinga2 – Understanding checks and notification types



Here I am trying to present (I hope in an easy way to understand) some Icinga concepts (maybe also applicable in Nagios) like active and passive checks, enabling and disabling freshness checks, soft and hard states,… and the related parameters to configure them.

ACTIVE and PASSIVE services

There are two types of services:

  • ACTIVE: Check initiated by the Icinga
Read more

Linux   Linux – Exim: Authenticated and TLS mail through smarthost



Exim is a very flexible and common MTA (mail transfer agent) in Unix systems.
This posts shows the way to configure Exim as client to send authenticated and encrypted (TLS) emails through a smarthost.

Lets suppose the smarthost email server is listening on port 587 for secure outgoing SMTP…

Configure exim to use the smarthost

To configure exim In … Read more

Linux   Linux – TCP listener daemon with tcpserver



To configure passive checks in Nagios/icinga I use a tcp listener daemon that launches a script (See Nagios – Using passive checks without agent)
Tried to use inetd superserver daemon, but in the last versions, i have not been able to make it work correctly (See last update in my post: Linux – cannot found / missing inetd.conf)Read more

Linux   Linux – cannot found / missing inetd.conf



Trying to configure a new inetd service needed for my Icinga (see Linux – Create custom inetd service), but i have not been able to find the inetd.conf file.
It seems inetd is not installed by default in the last Debian versions (mine is 9 – stretch).

Luckily, it is packetized in the inetutils-inetd

# apt-get install inetutils-inetd
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Linux   Linux – Create multiboot CD combining multiple ISO images



This post shows the steps to create a multiboot cd with multiple Linux distributions or tools.

For example, I created a recovery / disaster case cd with the following tools:
Clonezilla (to clone/recover disks and partitions)
Gparted (partition editior with GUI)
Trinity Rescue Kit (linux distribution for recovery and repair operations on Windows machines)

The Multicd Read more

Raspberry icon   Rasbperry – NO-IP configuration to be ran at boot time



If you need to update automatically a DNS entry with your public IP address (for example, to allow remote access to your home Raspberry or Linux), you can use the no-ip provider and its Linux or Raspberry client.

This posts shows the way to install the client and how to configure it to be started at boot time.

Register at

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Security   Security – Convert PFX to PEM using Windows or Linux



For certain application, a job partner asked me to send him certain certificate with private key in PEM format. Normally I’m using PFX format, but with a little help of the openssl toolkit converting PFX to PEM is quite easy.

Windows

openssl for windows can be downloaded here: http://gnuwin32.sourceforge.net/packages/openssl.htm
After extracting the contents, inside the bin subfolder the openssl … Read more

Linux   Linux – Running top command remotely (SSH)



Maybe you have tried to execute the top command to monitor processes on a remote host.

Error remotely – Run it in batch mode

If so, the following error can be returned:

$ ssh user@remotehost top -n1
TERM environment variable not set.

top does not work remotely in the default “interactive” mode. Use the “-b” parameter to run it in Read more