One of the benefits of LVM (Logical Volume Manager) is the possibility to extend LVM based storage by adding new Physical Volumes which together form LVM Volume Group. Adding new Physical Volume increases the capacity of the whole Volume Group by the capacity of that particular Physical Volume and can be performed online without any outages in LVM activity.
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LVM (Logical Volume Manager) gives us the ability to create Snapshots. LVM Snapshot is a logical volume that temporarily preserves the original data of changing logical volume, so it’s data can be backed up preserving consistency. Snapshot must be created prior to any critical modifications on the Logical Volume in order to fulfill it’s role.
Note: Snapshot Volume needs to be large enough to store the data that will change while it exists. If more data changes than the Snapshot can hold, the Snapshot will become unusable. That means we have to “predict” how much data will be changed on the original Volume while the Snapshot exists to let the Snapshot hold all those data changes.
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Nagios is a free software, which offers monitoring and alerting services for servers, switches, applications and services.
This tutorial describes simple Nagios Core and Nagios Plugins installation from rpm packages on CentOS 7 / RedHat 7. There is no need to configure and compile Nagios Core tar.gz based source files unless you really need the newest version.
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In this tutorial we will install OpenStack Kilo release from RDO repository on three nodes (Controller, Network, Compute) based on CentOS 7 operating system using packstack automated script. The following installation utilizes VLAN based internal software network infrastructure for communication between instances.
Environment used:
public network (Floating IP network): 192.168.2.0/24
internal network (on each node): no IP space, physical connection only (eth1)
controller node public IP: 192.168.2.12 (eth0)
network node public IP: 192.168.2.13 (eth0)
compute node public IP: 192.168.2.14 (eth0)
OS version (each node): CentOS Linux release 7.2.1511 (Core)
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Once our Red Hat 7 system is installed, it should be registered at RHN using Subscription Manager in order to be able to get newest updates. If the server is placed in network behind firewall and outgoing traffic is blocked by firewall, the only reliable way of keeping our Red Hat 7 up-to-date is through proxy (if any exists).
Below we will show you in 2 simple steps, how to configure HTTP Proxy for Red Hat Subscription Manager and register Red Hat 7 with RHN in command line using HTTP Proxy:
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Have you ever wondered how to check network utilization by PID in Linux? Now it’s easy with nethogs application, which unlike other network utilization monitoring applications (nload, iftop) works like Linux top command, but displays network utilization per PID along with the network device used.
