Snapshot Instance Operation Details-5 minutes a day to play OpenStack (36)

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In this section we discuss instance snapshot operations in detail through the logs.

Sometimes the operating system is badly damaged and cannot be repaired by Rescue operation, so we have to consider restoring it through backup. Of course, if we had done a backup of instance before.

The Nova backup operation is called Snapshot, which works by making a full backup of the instance image file (System disk), generating an image of type Snapshot, and then saving it to Glance.

The operation restored from backup is called Rebuild, which is discussed in the next section.

Here is the flowchart of snapshot instance

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1. Send a request to NOVA-API

2. Nova-api sending messages

3. Nova-compute Performing actions

Let's discuss each step in detail below.

send a request to Nova-api

The customer (which can be an OpenStack end user or another program) sends a request to the API (NOVA-API): "Take a snapshot of this Instance"

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View Log/opt/stack/logs/n-api.log

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Nova-api sending Messages

Nova-api sent a message to Messaging (RabbitMQ): "Take a snapshot of this Instance" source code in/opt/stack/nova/nova/compute/api.py, by snapshot.

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Nova-compute Performing Actions

View Log/opt/stack/logs/n-cpu.log

Pause instance

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Take a snapshot of the instance image file

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Recovery instance

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Uploading snapshots to Glance

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Snapshot successfully saved in Glance

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instance backup was successful and we discussed how to recover through snapshot in the next section.

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Snapshot Instance Operation Details-5 minutes a day to play OpenStack (36)