How to Extend Subnet Allocation Pool in OpenStack

extend subnet IP allocation pool in neutron
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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Encrypt Linux Partition using LUKS cryptsetup

encrypt linux volume using luks cryptsetup
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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Extend LVM Volume Group with the new Hard Disk

Extend LVM Volume Group
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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Backup and Restore Logical Volume using LVM Snapshot

Backup Restore LVM using Snapshot
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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