Update the snapshot agent documentation(#4758)

Detail the S3 permissions required in addition to a gotcha regarding having part of the key within the S3 bucket name configuration.
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Matt Keeler 2018-10-05 13:55:06 -04:00 committed by GitHub
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@ -176,6 +176,7 @@ if desired.
#### S3 Storage Options
Note that despite the AWS references, any S3-compatible endpoint can be specified with `-aws-s3-endpoint`.
* `-aws-access-key-id` and `-aws-secret-access-key` - These arguments supply
authentication information for connecting to S3. These may also be supplied using
the following alternative methods:<br>
@ -186,7 +187,8 @@ Note that despite the AWS references, any S3-compatible endpoint can be specifie
- EC2 instance role metadata
* `-aws-s3-bucket` - S3 bucket to use. Required for S3 storage, and setting this
disables local storage.
disables local storage. This should be only the bucket name without any
part of the key prefix.
* `-aws-s3-key-prefix` - Prefix to use for snapshot files in S3. Defaults to
"consul-snapshot".
@ -205,6 +207,49 @@ Note that despite the AWS references, any S3-compatible endpoint can be specifie
* `-aws-s3-kms-key` - Optional Amazon KMS key to use, if this is not set the default KMS master key will be used. Set this if you want to manage key rotation yourself.
#### S3 Required Permissions
Different S3 permissions are required depending on the configuration of the snapshot agent. In particular extra permissions are required when
snapshot rotation is enabled. S3 storage snapshot rotation is enabled when the `retain` configuration is greater than 0 and when there is
no `aws-s3-static-snapshot-name` configured.
| Permission | Resource | When you need it |
| -------------------- | ---------------------------------- | ----------------------------------------------- |
| `PutObject` | `arn:aws:s3:::<bucket name>/<key>` | Required for all operations. |
| `DeleteObject` | `arn:aws:s3:::<bucket name>/<key>` | Required only when snapshot rotation is enabled |
| `ListBucket` | `arn:aws:s3:::<bucket name>` | Required only when snapshot rotation is enabled |
| `ListBucketVersions` | `arn:aws:s3:::<bucket name>` | Required only when snapshot rotation is enabled |
Within the table `<key>` refers to the the key used to store the snapshot. When `aws-s3-static-snapshot-name` is configured the `<key>` is simply the value of that configuration. Otherwise the `<key>` will be the `<aws-s3-key-prefix configuration>/consul-*.snap`.
The following example IAM policy document assumes that the `aws-s3-bucket` is `consul-data` with defaults for `aws-s3-key-prefix`, `aws-s3-static-snapshot-name` and `retain`:
```json
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "",
"Effect": "Allow",
"Action": [
"s3:PutObject",
"s3:DeleteObject"
],
"Resource": "arn:aws:s3:::consul-data/consul-snapshots/consul-*.snap"
},
{
"Sid": "",
"Effect": "Allow",
"Action": [
"s3:ListBucketVersions",
"s3:ListBucket"
],
"Resource": "arn:aws:s3:::consul-data"
}
]
}
```
## Examples
Running the agent with no arguments will run a long-running daemon process that will