OpenStack Snapshots can be utilized to backup Instance before some critical changes are made on Instance OS or to migrate Instance to the new OpenStack Cloud.
In this tutorial we will create snapshot from existing Instance to launch it in different Cloud, but you can also create snapshot just to backup the Instance and restore it’s state later in the same Cloud, if needed.
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After OpenStack installation it can turn out, that the IP allocation pool of the subnet, we have just created is too small. If the allocation pool refers to public / provider network, we will quickly run out of free Floating IPs. Moreover, OpenStack Dashboard (Horizon) doesn’t provide the ability to extend or modify subnet IP alocation pool of already created subnet with already allocated IPs. But we can use dirty workaround and manually edit MariaDB which stores Openstack configuration data.
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LUKS (Linux Unified Key Setup) is encryption standard designed for Linux to encrypt Linux volumes or partitions. The implementation of LUKS is based on cryptsetup script as a basic disk encryption backend tool.
In this tutorial we will create Linux partition on KVM based CentOS 7, encrypt partition using LUKS cryptsetup and mount it permanently in particular mount point.
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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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