VictoriaMetrics/app/vmbackup/README.md

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# vmbackup
`vmbackup` creates VictoriaMetrics data backups from [instant snapshots](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-work-with-snapshots).
`vmbackup` supports incremental and full backups. Incremental backups are created automatically if the destination path already contains data from the previous backup.
Full backups can be sped up with `-origin` pointing to an already existing backup on the same remote storage. In this case `vmbackup` makes server-side copy for the shared
data between the existing backup and new backup. It saves time and costs on data transfer.
Backup process can be interrupted at any time. It is automatically resumed from the interruption point when restarting `vmbackup` with the same args.
Backed up data can be restored with [vmrestore](https://docs.victoriametrics.com/vmrestore.html).
See [this article](https://medium.com/@valyala/speeding-up-backups-for-big-time-series-databases-533c1a927883) for more details.
See also [vmbackupmanager](https://docs.victoriametrics.com/vmbackupmanager.html) tool built on top of `vmbackup`. This tool simplifies
creation of hourly, daily, weekly and monthly backups.
## Supported storage types
`vmbackup` supports the following `-dst` storage types:
* [GCS](https://cloud.google.com/storage/). Example: `gs://<bucket>/<path/to/backup>`
* [S3](https://aws.amazon.com/s3/). Example: `s3://<bucket>/<path/to/backup>`
* [Azure Blob Storage](https://azure.microsoft.com/en-us/products/storage/blobs/). Example: `azblob://<container>/<path/to/backup>`
* Any S3-compatible storage such as [MinIO](https://github.com/minio/minio), [Ceph](https://docs.ceph.com/en/pacific/radosgw/s3/) or [Swift](https://platform.swiftstack.com/docs/admin/middleware/s3_middleware.html). See [these docs](#advanced-usage) for details.
* Local filesystem. Example: `fs://</absolute/path/to/backup>`. Note that `vmbackup` prevents from storing the backup into the directory pointed by `-storageDataPath` command-line flag, since this directory should be managed solely by VictoriaMetrics or `vmstorage`.
## Use cases
### Regular backups
Regular backup can be performed with the following command:
```console
./vmbackup -storageDataPath=</path/to/victoria-metrics-data> -snapshot.createURL=http://localhost:8428/snapshot/create -dst=gs://<bucket>/<path/to/new/backup>
```
* `</path/to/victoria-metrics-data>` - path to VictoriaMetrics data pointed by `-storageDataPath` command-line flag in single-node VictoriaMetrics or in cluster `vmstorage`.
There is no need to stop VictoriaMetrics for creating backups since they are performed from immutable [instant snapshots](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-work-with-snapshots).
* `http://victoriametrics:8428/snapshot/create` is the url for creating snapshots according to [these docs](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-work-with-snapshots). `vmbackup` creates a snapshot by querying the provided `-snapshot.createURL`, then performs the backup and then automatically removes the created snapshot.
* `<bucket>` is an already existing name for [GCS bucket](https://cloud.google.com/storage/docs/creating-buckets).
* `<path/to/new/backup>` is the destination path where new backup will be placed.
### Regular backups with server-side copy from existing backup
If the destination GCS bucket already contains the previous backup at `-origin` path, then new backup can be sped up
with the following command:
```console
./vmbackup -storageDataPath=</path/to/victoria-metrics-data> -snapshot.createURL=http://localhost:8428/snapshot/create -dst=gs://<bucket>/<path/to/new/backup> -origin=gs://<bucket>/<path/to/existing/backup>
```
It saves time and network bandwidth costs by performing server-side copy for the shared data from the `-origin` to `-dst`.
### Incremental backups
Incremental backups are performed if `-dst` points to an already existing backup. In this case only new data is uploaded to remote storage.
It saves time and network bandwidth costs when working with big backups:
```console
./vmbackup -storageDataPath=</path/to/victoria-metrics-data> -snapshot.createURL=http://localhost:8428/snapshot/create -dst=gs://<bucket>/<path/to/existing/backup>
```
### Smart backups
Smart backups mean storing full daily backups into `YYYYMMDD` folders and creating incremental hourly backup into `latest` folder:
* Run the following command every hour:
```console
./vmbackup -storageDataPath=</path/to/victoria-metrics-data> -snapshot.createURL=http://localhost:8428/snapshot/create -dst=gs://<bucket>/latest
```
Where `<latest-snapshot>` is the latest [snapshot](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-work-with-snapshots).
The command will upload only changed data to `gs://<bucket>/latest`.
* Run the following command once a day:
```console
./vmbackup -storageDataPath=</path/to/victoria-metrics-data> -snapshot.createURL=http://localhost:8428/snapshot/create -dst=gs://<bucket>/<YYYYMMDD> -origin=gs://<bucket>/latest
```
Where `<daily-snapshot>` is the snapshot for the last day `<YYYYMMDD>`.
This approach saves network bandwidth costs on hourly backups (since they are incremental) and allows recovering data from either the last hour (`latest` backup)
or from any day (`YYYYMMDD` backups). Note that hourly backup shouldn't run when creating daily backup.
Do not forget to remove old backups when they are no longer needed in order to save storage costs.
See also [vmbackupmanager tool](https://docs.victoriametrics.com/vmbackupmanager.html) for automating smart backups.
### Server-side copy of the existing backup
Sometimes it is needed to make server-side copy of the existing backup. This can be done by specifying the source backup path via `-origin` command-line flag,
while the destination path for backup copy must be specified via `-dst` command-line flag. For example, the following command copies backup
from `gs://bucket/foo` to `gs://bucket/bar`:
```console
./vmbackup -origin=gs://bucket/foo -dst=gs://bucket/bar
```
The `-origin` and `-dst` must point to the same object storage bucket or to the same filesystem.
The server-side backup copy is usually performed at much faster speed comparing to the usual backup, since backup data isn't transferred
between the remote storage and locally running `vmbackup` tool.
If the `-dst` already contains some data, then its' contents is synced with the `-origin` data. This allows making incremental server-side copies of backups.
## How does it work?
The backup algorithm is the following:
1. Create a snapshot by querying the provided `-snapshot.createURL`
1. Collect information about files in the created snapshot, in the `-dst` and in the `-origin`.
1. Determine which files in `-dst` are missing in the created snapshot, and delete them. These are usually small files, which are already merged into bigger files in the snapshot.
1. Determine which files in the created snapshot are missing in `-dst`. These are usually small new files and bigger merged files.
1. Determine which files from step 3 exist in the `-origin`, and perform server-side copy of these files from `-origin` to `-dst`.
These are usually the biggest and the oldest files, which are shared between backups.
1. Upload the remaining files from step 3 from the created snapshot to `-dst`.
1. Delete the created snapshot.
The algorithm splits source files into 1 GiB chunks in the backup. Each chunk is stored as a separate file in the backup.
Such splitting balances between the number of files in the backup and the amounts of data that needs to be re-transferred after temporary errors.
`vmbackup` relies on [instant snapshot](https://medium.com/@valyala/how-victoriametrics-makes-instant-snapshots-for-multi-terabyte-time-series-data-e1f3fb0e0282) properties:
* All the files in the snapshot are immutable.
* Old files are periodically merged into new files.
* Smaller files have higher probability to be merged.
* Consecutive snapshots share many identical files.
These properties allow performing fast and cheap incremental backups and server-side copying from `-origin` paths.
See [this article](https://medium.com/@valyala/speeding-up-backups-for-big-time-series-databases-533c1a927883) for more details.
`vmbackup` can work improperly or slowly when these properties are violated.
## Troubleshooting
* If the backup is slow, then try setting higher value for `-concurrency` flag. This will increase the number of concurrent workers that upload data to backup storage.
* If `vmbackup` eats all the network bandwidth or CPU, then either decrease the `-concurrency` command-line flag value or set `-maxBytesPerSecond` command-line flag value to lower value.
* If `vmbackup` consumes all the CPU on systems with big number of CPU cores, then try running it with `-filestream.disableFadvise` command-line flag.
* If `vmbackup` has been interrupted due to temporary error, then just restart it with the same args. It will resume the backup process.
* Backups created from [single-node VictoriaMetrics](https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html) cannot be restored
at [cluster VictoriaMetrics](https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html) and vice versa.
## Advanced usage
### Providing credentials as a file
Obtaining credentials from a file.
Add flag `-credsFilePath=/etc/credentials` with the following content:
- for S3 (AWS, MinIO or other S3 compatible storages):
```console
[default]
aws_access_key_id=theaccesskey
aws_secret_access_key=thesecretaccesskeyvalue
```
- for GCP cloud storage:
```json
{
"type": "service_account",
"project_id": "project-id",
"private_key_id": "key-id",
"private_key": "-----BEGIN PRIVATE KEY-----\nprivate-key\n-----END PRIVATE KEY-----\n",
"client_email": "service-account-email",
"client_id": "client-id",
"auth_uri": "https://accounts.google.com/o/oauth2/auth",
"token_uri": "https://accounts.google.com/o/oauth2/token",
"auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
"client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/service-account-email"
}
```
### Providing credentials via env variables
Obtaining credentials from env variables.
- For AWS S3 compatible storages set env variable `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY`.
Also you can set env variable `AWS_SHARED_CREDENTIALS_FILE` with path to credentials file.
- For GCE cloud storage set env variable `GOOGLE_APPLICATION_CREDENTIALS` with path to credentials file.
- For Azure storage either set env variables `AZURE_STORAGE_ACCOUNT_NAME` and `AZURE_STORAGE_ACCOUNT_KEY`, or `AZURE_STORAGE_ACCOUNT_CONNECTION_STRING`.
Please, note that `vmbackup` will use credentials provided by cloud providers metadata service [when applicable](https://docs.victoriametrics.com/vmbackup.html#using-cloud-providers-metadata-service).
### Using cloud providers metadata service
`vmbackup` and `vmbackupmanager` will automatically use cloud providers metadata service in order to obtain credentials if they are running in cloud environment
and credentials are not explicitly provided via flags or env variables.
### Providing credentials in Kubernetes
The simplest way to provide credentials in Kubernetes is to use [Secrets](https://kubernetes.io/docs/concepts/configuration/secret/)
and inject them into the pod as environment variables. For example, the following secret can be used for AWS S3 credentials:
```yaml
apiVersion: v1
kind: Secret
metadata:
name: vmbackup-credentials
data:
access_key: key
secret_key: secret
```
And then it can be injected into the pod as environment variables:
```yaml
...
env:
- name: AWS_ACCESS_KEY_ID
valueFrom:
secretKeyRef:
key: access_key
name: vmbackup-credentials
- name: AWS_SECRET_ACCESS_KEY
valueFrom:
secretKeyRef:
key: secret_key
name: vmbackup-credentials
...
```
A more secure way is to use IAM roles to provide tokens for pods instead of managing credentials manually.
For AWS deployments it will be required to configure [IAM roles for service accounts](https://docs.aws.amazon.com/eks/latest/userguide/iam-roles-for-service-accounts.html).
In order to use IAM roles for service accounts with `vmbackup` or `vmbackupmanager` it is required to create ServiceAccount with IAM role mapping:
```yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: monitoring-backups
annotations:
eks.amazonaws.com/role-arn: arn:aws:iam::{ACCOUNT_ID}:role/{ROLE_NAME}
```
And [configure pod to use service account](https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/).
After this `vmbackup` and `vmbackupmanager` will automatically use IAM role for service account in order to obtain credentials.
For GCP deployments it will be required to configure [Workload Identity](https://cloud.google.com/kubernetes-engine/docs/how-to/workload-identity).
In order to use Workload Identity with `vmbackup` or `vmbackupmanager` it is required to create ServiceAccount with Workload Identity annotation:
```yaml
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: monitoring-backups
annotations:
iam.gke.io/gcp-service-account: {sa_name}@{project_name}.iam.gserviceaccount.com
```
And [configure pod to use service account](https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/).
After this `vmbackup` and `vmbackupmanager` will automatically use Workload Identity for servicpe account in order to obtain credentials.
### Using custom S3 endpoint
Usage with s3 custom url endpoint. It is possible to use `vmbackup` with s3 compatible storages like minio, cloudian, etc.
You have to add a custom url endpoint via flag:
- for MinIO
```console
-customS3Endpoint=http://localhost:9000
```
- for aws gov region
```console
-customS3Endpoint=https://s3-fips.us-gov-west-1.amazonaws.com
```
### Command-line flags
Run `vmbackup -help` in order to see all the available options:
```console
-concurrency int
The number of concurrent workers. Higher concurrency may reduce backup duration (default 10)
-configFilePath string
Path to file with S3 configs. Configs are loaded from default location if not set.
See https://docs.aws.amazon.com/general/latest/gr/aws-security-credentials.html
-configProfile string
Profile name for S3 configs. If no set, the value of the environment variable will be loaded (AWS_PROFILE or AWS_DEFAULT_PROFILE), or if both not set, DefaultSharedConfigProfile is used
-credsFilePath string
Path to file with GCS or S3 credentials. Credentials are loaded from default locations if not set.
See https://cloud.google.com/iam/docs/creating-managing-service-account-keys and https://docs.aws.amazon.com/general/latest/gr/aws-security-credentials.html
-customS3Endpoint string
Custom S3 endpoint for use with S3-compatible storages (e.g. MinIO). S3 is used if not set
-dst string
Where to put the backup on the remote storage. Example: gs://bucket/path/to/backup, s3://bucket/path/to/backup, azblob://container/path/to/backup or fs:///path/to/local/backup/dir
-dst can point to the previous backup. In this case incremental backup is performed, i.e. only changed data is uploaded
-enableTCP6
Whether to enable IPv6 for listening and dialing. By default, only IPv4 TCP and UDP are used
-envflag.enable
Whether to enable reading flags from environment variables in addition to the command line. Command line flag values have priority over values from environment vars. Flags are read only from the command line if this flag isn't set. See https://docs.victoriametrics.com/#environment-variables for more details
-envflag.prefix string
Prefix for environment variables if -envflag.enable is set
-eula
Deprecated, please use -license or -licenseFile flags instead. By specifying this flag, you confirm that you have an enterprise license and accept the ESA https://victoriametrics.com/legal/esa/ . This flag is available only in VictoriaMetrics enterprise. See https://docs.victoriametrics.com/enterprise.html
-filestream.disableFadvise
Whether to disable fadvise() syscall when reading large data files. The fadvise() syscall prevents from eviction of recently accessed data from OS page cache during background merges and backups. In some rare cases it is better to disable the syscall if it uses too much CPU
-flagsAuthKey string
Auth key for /flags endpoint. It must be passed via authKey query arg. It overrides httpAuth.* settings
-fs.disableMmap
Whether to use pread() instead of mmap() for reading data files. By default, mmap() is used for 64-bit arches and pread() is used for 32-bit arches, since they cannot read data files bigger than 2^32 bytes in memory. mmap() is usually faster for reading small data chunks than pread()
-http.connTimeout duration
Incoming http connections are closed after the configured timeout. This may help to spread the incoming load among a cluster of services behind a load balancer. Please note that the real timeout may be bigger by up to 10% as a protection against the thundering herd problem (default 2m0s)
-http.disableResponseCompression
Disable compression of HTTP responses to save CPU resources. By default, compression is enabled to save network bandwidth
-http.idleConnTimeout duration
Timeout for incoming idle http connections (default 1m0s)
-http.maxGracefulShutdownDuration duration
The maximum duration for a graceful shutdown of the HTTP server. A highly loaded server may require increased value for a graceful shutdown (default 7s)
-http.pathPrefix string
An optional prefix to add to all the paths handled by http server. For example, if '-http.pathPrefix=/foo/bar' is set, then all the http requests will be handled on '/foo/bar/*' paths. This may be useful for proxied requests. See https://www.robustperception.io/using-external-urls-and-proxies-with-prometheus
-http.shutdownDelay duration
Optional delay before http server shutdown. During this delay, the server returns non-OK responses from /health page, so load balancers can route new requests to other servers
-httpAuth.password string
Password for HTTP server's Basic Auth. The authentication is disabled if -httpAuth.username is empty
-httpAuth.username string
Username for HTTP server's Basic Auth. The authentication is disabled if empty. See also -httpAuth.password
-httpListenAddr string
TCP address for exporting metrics at /metrics page (default ":8420")
-internStringCacheExpireDuration duration
The expiry duration for caches for interned strings. See https://en.wikipedia.org/wiki/String_interning . See also -internStringMaxLen and -internStringDisableCache (default 6m0s)
-internStringDisableCache
Whether to disable caches for interned strings. This may reduce memory usage at the cost of higher CPU usage. See https://en.wikipedia.org/wiki/String_interning . See also -internStringCacheExpireDuration and -internStringMaxLen
-internStringMaxLen int
The maximum length for strings to intern. A lower limit may save memory at the cost of higher CPU usage. See https://en.wikipedia.org/wiki/String_interning . See also -internStringDisableCache and -internStringCacheExpireDuration (default 500)
-license string
See https://victoriametrics.com/products/enterprise/ for trial license. This flag is available only in VictoriaMetrics enterprise. See https://docs.victoriametrics.com/enterprise.html
-license.forceOffline
See https://victoriametrics.com/products/enterprise/ for trial license. This flag is available only in VictoriaMetrics enterprise. See https://docs.victoriametrics.com/enterprise.html
-licenseFile string
See https://victoriametrics.com/products/enterprise/ for trial license. This flag is available only in VictoriaMetrics enterprise. See https://docs.victoriametrics.com/enterprise.html
-loggerDisableTimestamps
Whether to disable writing timestamps in logs
-loggerErrorsPerSecondLimit int
Per-second limit on the number of ERROR messages. If more than the given number of errors are emitted per second, the remaining errors are suppressed. Zero values disable the rate limit
-loggerFormat string
Format for logs. Possible values: default, json (default "default")
-loggerJSONFields string
Allows renaming fields in JSON formatted logs. Example: "ts:timestamp,msg:message" renames "ts" to "timestamp" and "msg" to "message". Supported fields: ts, level, caller, msg
-loggerLevel string
Minimum level of errors to log. Possible values: INFO, WARN, ERROR, FATAL, PANIC (default "INFO")
-loggerOutput string
Output for the logs. Supported values: stderr, stdout (default "stderr")
-loggerTimezone string
Timezone to use for timestamps in logs. Timezone must be a valid IANA Time Zone. For example: America/New_York, Europe/Berlin, Etc/GMT+3 or Local (default "UTC")
-loggerWarnsPerSecondLimit int
Per-second limit on the number of WARN messages. If more than the given number of warns are emitted per second, then the remaining warns are suppressed. Zero values disable the rate limit
-maxBytesPerSecond size
The maximum upload speed. There is no limit if it is set to 0
Supports the following optional suffixes for size values: KB, MB, GB, TB, KiB, MiB, GiB, TiB (default 0)
-memory.allowedBytes size
Allowed size of system memory VictoriaMetrics caches may occupy. This option overrides -memory.allowedPercent if set to a non-zero value. Too low a value may increase the cache miss rate usually resulting in higher CPU and disk IO usage. Too high a value may evict too much data from the OS page cache resulting in higher disk IO usage
Supports the following optional suffixes for size values: KB, MB, GB, TB, KiB, MiB, GiB, TiB (default 0)
-memory.allowedPercent float
Allowed percent of system memory VictoriaMetrics caches may occupy. See also -memory.allowedBytes. Too low a value may increase cache miss rate usually resulting in higher CPU and disk IO usage. Too high a value may evict too much data from the OS page cache which will result in higher disk IO usage (default 60)
-metricsAuthKey string
Auth key for /metrics endpoint. It must be passed via authKey query arg. It overrides httpAuth.* settings
-origin string
Optional origin directory on the remote storage with old backup for server-side copying when performing full backup. This speeds up full backups
-pprofAuthKey string
Auth key for /debug/pprof/* endpoints. It must be passed via authKey query arg. It overrides httpAuth.* settings
-pushmetrics.extraLabel array
Optional labels to add to metrics pushed to -pushmetrics.url . For example, -pushmetrics.extraLabel='instance="foo"' adds instance="foo" label to all the metrics pushed to -pushmetrics.url
Supports an array of values separated by comma or specified via multiple flags.
-pushmetrics.interval duration
Interval for pushing metrics to -pushmetrics.url (default 10s)
-pushmetrics.url array
Optional URL to push metrics exposed at /metrics page. See https://docs.victoriametrics.com/#push-metrics . By default, metrics exposed at /metrics page aren't pushed to any remote storage
Supports an array of values separated by comma or specified via multiple flags.
-s2a_enable_appengine_dialer
If true, opportunistically use AppEngine-specific dialer to call S2A.
-s2a_timeout duration
Timeout enforced on the connection to the S2A service for handshake. (default 3s)
-s3ForcePathStyle
Prefixing endpoint with bucket name when set false, true by default. (default true)
-s3StorageClass string
The Storage Class applied to objects uploaded to AWS S3. Supported values are: GLACIER, DEEP_ARCHIVE, GLACIER_IR, INTELLIGENT_TIERING, ONEZONE_IA, OUTPOSTS, REDUCED_REDUNDANCY, STANDARD, STANDARD_IA.
See https://docs.aws.amazon.com/AmazonS3/latest/userguide/storage-class-intro.html/
-snapshot.createURL string
VictoriaMetrics create snapshot url. When this is given a snapshot will automatically be created during backup. Example: http://victoriametrics:8428/snapshot/create . There is no need in setting -snapshotName if -snapshot.createURL is set
-snapshot.deleteURL string
VictoriaMetrics delete snapshot url. Optional. Will be generated from -snapshot.createURL if not provided. All created snapshots will be automatically deleted. Example: http://victoriametrics:8428/snapshot/delete
-snapshotName string
Name for the snapshot to backup. See https://docs.victoriametrics.com/Single-server-VictoriaMetrics.html#how-to-work-with-snapshots. There is no need in setting -snapshotName if -snapshot.createURL is set
-storageDataPath string
Path to VictoriaMetrics data. Must match -storageDataPath from VictoriaMetrics or vmstorage (default "victoria-metrics-data")
-tls
Whether to enable TLS for incoming HTTP requests at -httpListenAddr (aka https). -tlsCertFile and -tlsKeyFile must be set if -tls is set
-tlsCertFile string
Path to file with TLS certificate if -tls is set. Prefer ECDSA certs instead of RSA certs as RSA certs are slower. The provided certificate file is automatically re-read every second, so it can be dynamically updated
-tlsCipherSuites array
Optional list of TLS cipher suites for incoming requests over HTTPS if -tls is set. See the list of supported cipher suites at https://pkg.go.dev/crypto/tls#pkg-constants
Supports an array of values separated by comma or specified via multiple flags.
-tlsKeyFile string
Path to file with TLS key if -tls is set. The provided key file is automatically re-read every second, so it can be dynamically updated
-tlsMinVersion string
Optional minimum TLS version to use for incoming requests over HTTPS if -tls is set. Supported values: TLS10, TLS11, TLS12, TLS13
-version
Show VictoriaMetrics version
```
## How to build from sources
It is recommended using [binary releases](https://github.com/VictoriaMetrics/VictoriaMetrics/releases) - see `vmutils-*` archives there.
### Development build
1. [Install Go](https://golang.org/doc/install). The minimum supported version is Go 1.20.
1. Run `make vmbackup` from the root folder of [the repository](https://github.com/VictoriaMetrics/VictoriaMetrics).
It builds `vmbackup` binary and puts it into the `bin` folder.
### Production build
1. [Install docker](https://docs.docker.com/install/).
1. Run `make vmbackup-prod` from the root folder of [the repository](https://github.com/VictoriaMetrics/VictoriaMetrics).
It builds `vmbackup-prod` binary and puts it into the `bin` folder.
### Building docker images
Run `make package-vmbackup`. It builds `victoriametrics/vmbackup:<PKG_TAG>` docker image locally.
`<PKG_TAG>` is auto-generated image tag, which depends on source code in the repository.
The `<PKG_TAG>` may be manually set via `PKG_TAG=foobar make package-vmbackup`.
The base docker image is [alpine](https://hub.docker.com/_/alpine) but it is possible to use any other base image
by setting it via `<ROOT_IMAGE>` environment variable. For example, the following command builds the image on top of [scratch](https://hub.docker.com/_/scratch) image:
```console
ROOT_IMAGE=scratch make package-vmbackup
```