Centos cluster IP resource in stopped state – pacemaker

When a two nodes pcs cluster is created without a stonith device the below error may appear when creating an IPaddr2 cluster resource. After the creation the resource cannot be brought online.

In order to resolve the issue stonith-enabled setting should be disabled. Afterwards the resource would become online as shown on the below screenshot.

Corosync Cluster Engine exiting with status 8 – Failed to start

The below error can occur when one tries to create a new HA cluster with pcs package. Corosync fails to start with the below description.

Corosync error

The error can be resolved by editing /etc/hosts file and by commenting the first two lines for localhost. At the end I appended a new line that maps localhost with a specific IPv4 IP but this could be unnecessary.

After that when one tries to create and enable the cluster the result would be successful.

Rescan storage disk capacity physical RHEL – multipath storage device

Sometimes infrastructure servers are physical and directly connected to storage and not virtual ones. In virtualization cases, one has to assign a new virtual disk on the virtual server and proceed with the expand. In case of a physical server one should do the following in order to assign more space on a partition or a lvm.

Find storage adapters and rescan them:

where X is 0 to 10 in my system (some online and some offline)

After re scanning storage adapters a new multipath device will be visible and ready to be used.

4 paths are available for this storage device ( disk 50G)

Initialize your disk and use it appropriately.

Configure Postfix to Send Mail Using an External SMTP Server

Sometimes due to network configuration you cannot use your SMTP server and you want to send emails through a proxy/relay. Below you can find how to configure a linux machine so that to act as an SMTP relay and forward emails to one SMTP server.

First if not installed you should install postfix package for your linux server depending on the distribution. For example on a RedHat server you should do:

Then you should edit the below postfix configuration lines. Postfix configuration is handled by /etc/postfix/main.cf

  • Change inet_interfaces from localhsot to all

Configure the source from which the emails will be sent. For example you can use a specific host or a subnet of hosts. In my case I chose a subnet so the second line should be uncommented.

  • Configure your subnet source Address and mask.
  • Add your SMTP server address in the latest line

Finally test your configuration by a powershell command to verify the functionality.