New install guide for Skopeo

Author: jasonrandrews

content/install-guides/skopeo.md

@@ -0,0 +1,390 @@
+---
+title: Skopeo
+
+draft: true
+
+author_primary: Jason Andrews
+minutes_to_complete: 10
+official_docs: https://github.com/containers/skopeo
+
+additional_search_terms:
+- containers
+- images
+- registry
+
+layout: installtoolsall
+multi_install: false
+multitool_install_part: false
+test_images:
+- ubuntu:latest
+test_maintenance: false
+tool_install: true
+weight: 1
+---
+
+Skopeo is a command-line utility that performs various operations on container images and image repositories. It does not require a daemon to be running on your computer. 
+
+This article explains how to install Skopeo for Ubuntu on Arm.
+
+Skopeo is available for Windows, macOS, and Linux and supports the Arm architecture. Refer to [Installing Skopeo](https://github.com/containers/skopeo/blob/main/install.md) for information about other operating systems and architectures.
+
+## What should I consider before installing Skopeo on Arm?
+
+Confirm you are using an Arm machine by running:
+
+```bash
+uname -m
+```
+
+The output should be:
+```output
+aarch64
+```
+
+If you see a different result, you are not using an Arm computer running 64-bit Linux.
+
+## How do I download and Install Skopeo for Ubuntu on Arm?
+
+The easiest way to install Skopeo is to use the package manager:
+
+```bash
+sudo apt update
+sudo apt install -y skopeo
+```
+
+Confirm the installation by checking the version:
+
+```bash
+skopeo --version
+```
+
+To see the help message:
+
+```bash
+skopeo --help
+```
+
+The output is:
+
+```output
+Various operations with container images and container image registries
+
+Usage:
+  skopeo [flags]
+  skopeo [command]
+
+Available Commands:
+  copy                                          Copy an IMAGE-NAME from one location to another
+  delete                                        Delete image IMAGE-NAME
+  generate-sigstore-key                         Generate a sigstore public/private key pair
+  help                                          Help about any command
+  inspect                                       Inspect image IMAGE-NAME
+  list-tags                                     List tags in the transport/repository specified by the SOURCE-IMAGE
+  login                                         Login to a container registry
+  logout                                        Logout of a container registry
+  manifest-digest                               Compute a manifest digest of a file
+  standalone-sign                               Create a signature using local files
+  standalone-verify                             Verify a signature using local files
+  sync                                          Synchronize one or more images from one location to another
+
+Flags:
+      --command-timeout duration   timeout for the command execution
+      --debug                      enable debug output
+  -h, --help                       help for skopeo
+      --insecure-policy            run the tool without any policy check
+      --override-arch ARCH         use ARCH instead of the architecture of the machine for choosing images
+      --override-os OS             use OS instead of the running OS for choosing images
+      --override-variant VARIANT   use VARIANT instead of the running architecture variant for choosing images
+      --policy string              Path to a trust policy file
+      --registries.d DIR           use registry configuration files in DIR (e.g. for container signature storage)
+      --tmpdir string              directory used to store temporary files
+  -v, --version                    Version for Skopeo
+
+Use "skopeo [command] --help" for more information about a command.
+```
+
+## How do I get started with Skopeo?
+
+Some commands to get you started with Skopeo are demonstrated below.
+
+### How can I check if a container image supports Arm?
+
+To find out if an image is multi-architecture, including Arm, you can inspect the image's manifest.
+
+For example, to check if the dev container available for creating Arm Learning Paths supports the Arm architecture run:
+
+```bash
+skopeo inspect --raw docker://docker.io/armswdev/learn-dev-container:latest | jq '.manifests[] | select(.platform.architecture == "arm64")'
+```
+
+The output is similar to:
+
+```output
+{
+  "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+  "size": 1574,
+  "digest": "sha256:b7abfdc06d4cb06dfbb644f0d7c50202f99f83298da7903ea6463de23b55fb10",
+  "platform": {
+    "architecture": "arm64",
+    "os": "linux"
+  }
+}
+```
+
+If the command returns a result for an image, the image supports the `arm64` architecture.
+
+### How can I check if a container image supports multiple architectures?
+
+To find out if an image supports both `arm64` and `amd64` architectures, you can inspect the image's manifest for both architectures.
+
+For example, to check if the same dev container supports both architectures run:
+
+```bash
+skopeo inspect --raw docker://docker.io/armswdev/learn-dev-container:latest | jq '.manifests[] | select(.platform.architecture == "arm64" or .platform.architecture == "amd64")'
+```
+
+The output confirms that both `arm64` and `amd64` are supported architectures as shown below:
+
+```output
+{
+  "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+  "size": 1574,
+  "digest": "sha256:15fe2dc0925c6e5da27048edcd034660f51216ad700cb7cf12cb7779c16e9bce",
+  "platform": {
+    "architecture": "amd64",
+    "os": "linux"
+  }
+}
+{
+  "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+  "size": 1574,
+  "digest": "sha256:b7abfdc06d4cb06dfbb644f0d7c50202f99f83298da7903ea6463de23b55fb10",
+  "platform": {
+    "architecture": "arm64",
+    "os": "linux"
+  }
+}
+```
+
+### Can I use a script to check if a container image supports the Arm architecture?
+
+You can run a script to check container images for `arm64` support.
+
+The script performs the following tasks:
+- Get a token for the repository
+- Read the image manifest
+- Check the manifest for architecture support 
+
+Make sure Python3 is installed on your computer. 
+
+Use a text editor to copy the Python code below to a file named `check-image.py`.
+
+```python
+import requests
+import sys
+import os
+import argparse
+from typing import List, Dict, Tuple
+
+# Target architectures to check
+TARGET_ARCHITECTURES = {'amd64', 'arm64'}
+TIMEOUT_SECONDS = 10
+
+def get_auth_token(repository: str) -> str:
+    """Get Docker Hub authentication token."""
+    url = "https://auth.docker.io/token"
+    params = {
+        "service": "registry.docker.io",
+        "scope": f"repository:{repository}:pull"
+    }
+    try:
+        response = requests.get(url, params=params, timeout=TIMEOUT_SECONDS)
+        response.raise_for_status()
+        return response.json()['token']
+    except requests.exceptions.RequestException as e:
+        print(f"Failed to get auth token: {e}", file=sys.stderr)
+        sys.exit(1)
+
+def get_manifest(repository: str, tag: str, token: str) -> Dict:
+    """Fetch manifest for specified image."""
+    headers = {
+        'Accept': 'application/vnd.docker.distribution.manifest.list.v2+json',
+        'Authorization': f'Bearer {token}'
+    }
+    url = f"https://registry-1.docker.io/v2/{repository}/manifests/{tag}"
+    try:
+        response = requests.get(url, headers=headers, timeout=TIMEOUT_SECONDS)
+        response.raise_for_status()
+        return response.json()
+    except requests.exceptions.RequestException as e:
+        print(f"Failed to get manifest: {e}", file=sys.stderr)
+        sys.exit(1)
+
+def check_architectures(manifest: Dict) -> List[str]:
+    """Check available architectures in the manifest."""
+    if manifest.get('manifests'):
+        archs = [m['platform']['architecture'] for m in manifest['manifests']]
+        return archs
+    else:
+        return []
+
+def parse_image_spec(image: str) -> Tuple[str, str]:
+    """Parse image specification into repository and tag."""
+    if ':' in image:
+        repository, tag = image.split(':', 1)
+    else:
+        repository, tag = image, 'latest'
+    
+    if '/' not in repository:
+        repository = f'library/{repository}'
+    return repository.lower(), tag
+
+def parse_args():
+    """Parse command line arguments."""
+    parser = argparse.ArgumentParser(description='Check Docker image architectures')
+    parser.add_argument('image', help='Docker image name (format: name:tag)')
+    return parser.parse_args()
+
+if __name__ == "__main__":
+    args = parse_args()
+    repository, tag = parse_image_spec(args.image)
+    
+    token = get_auth_token(repository)
+    manifest = get_manifest(repository, tag, token)
+    architectures = check_architectures(manifest)
+
+    if not architectures:
+        print(f"No architectures found for {args.image}", file=sys.stderr)
+        sys.exit(1)
+
+    available_targets = TARGET_ARCHITECTURES.intersection(architectures)
+    missing_targets = TARGET_ARCHITECTURES - set(architectures)
+
+    if not missing_targets:
+        print(f"✓ Image {args.image} supports all required architectures")
+    else:
+        print(f"✗ Image {args.image} is missing architectures: {', '.join(missing_targets)}")
+        print(f"Available architectures: {', '.join(architectures)}")
+```
+
+The script queries Docker Hub. If needed, you can change the registry and the architecture list to meet your needs.
+
+Run the script asking about Alpine Linux:
+
+```bash
+python3 ./check-image.py alpine:3.21.0
+```
+
+The output indicates that the image supports both `arm64` and `amd64`:
+
+```output
+✓ Image alpine:3.21.0 supports all required architectures
+```
+
+## What are some other uses for Skopeo?
+
+Copy an image from a registry to a local directory. This command is similar to `docker pull` and will copy the image from the remote registry to your local directory.
+
+```bash
+skopeo copy docker://docker.io/armswdev/uname:latest dir:./uname
+```
+
+The output is:
+
+```output
+Getting image source signatures
+Copying blob cd741b12a7ea done   |
+Copying config d11135df72 done   |
+Writing manifest to image destination
+```
+
+Inspect an image in a remote registry:
+
+```bash
+skopeo inspect docker://docker.io/armswdev/uname:latest
+```
+
+The output is:
+
+```output
+{
+    "Name": "docker.io/armswdev/uname",
+    "Digest": "sha256:4f1fe1e1e1ad179bb2cec6b3c8b458d6ead02bd7459798a357791353b867462d",
+    "RepoTags": [
+        "latest"
+    ],
+    "Created": "2023-03-08T04:32:41.063980445Z",
+    "DockerVersion": "",
+    "Labels": {
+        "org.opencontainers.image.ref.name": "ubuntu",
+        "org.opencontainers.image.version": "22.04"
+    },
+    "Architecture": "arm64",
+    "Os": "linux",
+    "Layers": [
+        "sha256:cd741b12a7eaa64357041c2d3f4590c898313a7f8f65cd1577594e6ee03a8c38"
+    ],
+    "LayersData": [
+        {
+            "MIMEType": "application/vnd.oci.image.layer.v1.tar+gzip",
+            "Digest": "sha256:cd741b12a7eaa64357041c2d3f4590c898313a7f8f65cd1577594e6ee03a8c38",
+            "Size": 27347481,
+            "Annotations": null
+        }
+    ],
+    "Env": [
+        "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
+    ]
+}
+```
+
+List tags in a remote registry for the Ubuntu image with many tags:
+
+```bash
+skopeo list-tags docker://docker.io/library/ubuntu
+```
+
+The partial output is:
+
+```output
+{
+    "Repository": "docker.io/library/ubuntu",
+    "Tags": [
+        "10.04",
+        "12.04",
+        "12.04.5",
+        "12.10",
+        "13.04",
+        "13.10",
+        "14.04",
+        "14.04.1",
+        "14.04.2",
+        "14.04.3",
+        "14.04.4",
+        "14.04.5",
+        "14.10",
+        "15.04",
+        "15.10",
+        "16.04",
+        "16.10",
+        "17.04",
+        "17.10",
+        "18.04",
+        "18.10",
+        "19.04",
+        "19.10",
+        "20.04",
+        "20.10",
+        "21.04",
+        "21.10",
+        "22.04",
+        "22.10",
+        "23.04",
+        "23.10",
+        "24.04",
+        "24.10",
+        "25.04",
+< many more tag with Ubuntu release names omitted>
+```
+
+You are ready to use Skopeo for your projects.