Blog Grid

Comment uncomment and replace characters in multiple lines in Vim

Modifying files in Vim can be arduous and time-consuming, especially when we want to modify multiple lines at once. The typical use case is modifying a configuration file in the system when it is required to comment or uncomment multiple lines at a time, or to replace the same character in many similar lines from the top to the bottom. Here are a few hints on how to facilitate multiple line modifications in text files using Vim editor.

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Resize Cinder based Volume attached to an Instance in OpenStack

One of the key features in OpenStack is the ability to resize the Instance’s flavor to increase resource limits used by Instances, such as vCPUs and RAM. Unfortunately, in the case of an Instance with a Cinder-backed volume, changing flavor does not affect the underlying volume.
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How To Enable LLDP Service on CentOS

LLDP (Link Layer Discovery Protocol) can be essential in situations of complex network-server infrastructure configurations and it’s extremely helpful in case there is no direct access to our setup but we need to determine what network ports on the switches are our servers NIC cards connected to.

Below we present how to install and enable LLDP Daemon on CentOS Linux, based on CinderCloud VPS, and check what are the corresponding neighbor port IDs connected to our server network cards.
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How to add Hot Spare Volume to the existing mdadm software RAID array

Having a Hot Spare significantly increases the security of our data in a RAID array. In the case of a single disk failure, a Hot Spare jumps in the place of a faulty drive. Working as a temporary replacement, a Hot Spare can potentially buy time for us before we swap the faulty drive with the new one.

In the below scenario we have an example CentOS 7, installed on top of RAID 1 (mirror) using mdadm software RAID. The array was created by the Anaconda installer script during OS installation, for more details refer to:
CentOS 7 Installation with LVM RAID 1 – Mirroring.
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Configure VLAN tagged interface over LACP bond on CentOS / RHEL

In one of my previous articles I presented how to:
Configure a bridge interface over a VLAN tagged bonded interface on CentOS / RHEL

This is a supplement to the above tutorial – sometimes all you need is to configure just a regular interface over a VLAN tagged bond and the below procedure describes how to do it on CentOS 7 / RHEL 7 in few easy steps.
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Configure a bridge interface over a VLAN tagged bonded interface on CentOS / RHEL

Linux enables us to create advanced network setups which provide us with special features like NIC Bonding, VLAN tagging or Bridging allowing us to increase network connectivity efficiency and reliability of Linux based hosts.

Linux Bond is a kernel module which facilitates combining multiple network interfaces (like ens1f0, ens1f1) into aggregated links named Bonds to provide network redundancy, link failover and increased throughput.

VLAN tagging (802.1q) helps us to distinguish particular VLANs from network trunk (VLANs range) coming from the switch. It’s very helpful Linux kernel module, which enables us to connect to the multiple networks, if the server has less NICs than networks.
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