### Initial hello-world example: snapcraft.yaml and hello.sh

Source: https://snapcraft.io/docs/reference/interfaces/ros-opt-data-interface

The initial hello-world example snap, before adding ros-opt-data. The snapcraft.yaml defines a simple dump-based snap, and hello.sh just prints "hello world". These two files are shown as the starting point for the tutorial.

```yaml
name: hello-world
version: '0.1'
summary: A simple hello world application
description: |
  A simple hello world application.
base: core22

grade: devel
confinement: strict

apps:
  hello-world:
    command: ./hello.sh

parts:
  hello-world:
    plugin: dump
    source: files

```

```bash
#!/bin/bash
echo "hello world"

```

--------------------------------

### Download a snap and its assertions with snap download

Source: https://snapcraft.io/docs/explanation/security/assertions

Example of using the `snap download` command to fetch a snap and its assertions. The output shows the download progress and instructions to install the snap using `snap ack` and `snap install`.

```bash
$ snap download gnome-calculator
Fetching snap "gnome-calculator"
Fetching assertions for "gnome-calculator"
Install the snap with:
   snap ack gnome-calculator_945.assert
   snap install gnome-calculator_945.snap

```

--------------------------------

### Install the core snap

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/raspberrypios

Install the core snap to get the latest snapd. The expected output is shown.

```bash
$ sudo snap install core
core 16-2.45.2 from Canonical✓ installed

```

--------------------------------

### Autostart desktop file example with snap.yaml and startup command

Source: https://snapcraft.io/docs/reference/development/yaml-schemas/the-snap-format

The snap.yaml sets the 'autostart' property to 'my-chat.desktop'. The desktop file in $SNAP_USER_DATA/.config/autostart provides the Exec line. The application is started as 'my-chat.chat --autostart a b c'.

```yaml
name: my-chat
version: 1.0
apps:
    chat:
        command: bin/my-chat
        autostart: my-chat.desktop

```

```ini
[Desktop Entry]
Name=My Chat
Exec=/usr/bin/my-chat --autostart a b c

```

```text
my-chat.chat --autostart a b c 

```

--------------------------------

### snapctl system-mode command and example output

Source: https://snapcraft.io/docs/how-to-guides/snap-development/use-snapctl

Returns YAML-formatted details about specific system states, including the current system mode, whether seeded snaps have finished installing, and whether the factory image hint is set. The output shown is an example of a UC20+ system in install mode with the factory hint enabled.

```bash
$ snapctl system-mode
system-mode: install
seed-loaded: true
factory: true

```

--------------------------------

### snap list output showing install modes

Source: https://snapcraft.io/docs/explanation/snap-development/install-modes

Example output of the snap list command showing the install mode in the Notes column. The Notes column displays devmode for snaps installed in developer mode and classic for classic snaps.

```text
Name        Version            Rev    Tracking        Publisher     Notes
liquidctl   1.7.1-11-g6295354  1      latest/stable   morrisong     devmode
snapcraft   5.0                6751   latest/stable   canonical✓    classic

```

--------------------------------

### snap debug timings --last=install output (cache and fresh install)

Source: https://snapcraft.io/docs/explanation/how-snaps-work/snap-performance

Example output from `snap debug timings --last=install` after installing the Chromium snap, first from cache and then fresh install. The `Doing` column shows task execution times.

```text
ID      Status        Doing      Undoing  Label                          Summary
160241  Done          461ms            -  prerequisites                  Ensure prerequisites for "chromium" are available
 ^                    353ms            -  install-prereq                 install "cups"
 ^                     12ms            -  install-prereq                 install base "core22"
160242  Done           62ms            -  download-snap                  Download snap "chromium" (2556) from channel "stable"
160243  Done          607ms            -  validate-snap                  Fetch and check assertions for snap "chromium" (2556)
160244  Done         2253ms            -  mount-snap                     Mount snap "chromium" (2556)
 ^                     75ms            -  check-snap                     check snap "chromium"
 ^                   2059ms            -  setup-snap                     setup snap "chromium"
160245  Done           61ms            -  copy-snap-data                 Copy snap "chromium" data
160246  Done          241ms            -  setup-profiles                 Setup snap "chromium" (2556) security profiles
 ^                     32ms            -  setup-security-backend         setup security backend "seccomp" for snap "chromium"
 ^                    133ms            -  setup-security-backend[many]   setup security backend "apparmor" for 1 snaps
  ^                   101ms            -  load-profiles[changed-many]    load changed security profiles of 1 snaps
160247  Done          396ms            -  link-snap                      Make snap "chromium" (2556) available to the system
 ^                      8ms            -  generate-wrappers              generate wrappers for snap chromium
 ^                    290ms            -  update-fc-cache                update font config caches
160248  Done          388ms            -  auto-connect                   Automatically connect eligible plugs and slots of snap "chromium"
160267  Done           92ms            -  connect                        Connect chromium:u2f-devices to snapd:u2f-devices
```

--------------------------------

### Install snap from explicit channel

Source: https://snapcraft.io/docs/explanation/how-snaps-work/channels-and-tracks

Installs a snap from an explicitly specified channel. Here, 'latest/edge' is used as an example, but any valid channel can be specified.

```bash
snap install vlc --channel=latest/edge

```

--------------------------------

### Install snap components with snap install

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/using-components

Installs the snap my-snap along with components comp1 and comp2. If the snap is already installed, only the missing components are installed. The syntax <snap_name>+<comp_1>+...+<comp_N> is used to refer to components from the command line.

```bash
snap install my-snap+comp1+comp2

```

--------------------------------

### Test snap installation with hello-world

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/arch-linux

Installs the hello-world snap and runs it to verify the system is set up correctly.

```bash
$ sudo snap install hello-world
hello-world 6.3 from Canonical✓ installed
$ hello-world
Hello World!

```

--------------------------------

### Install snaps as a single transaction with --transaction=all-snaps

Source: https://snapcraft.io/docs/explanation/how-snaps-work/transactional-updates

Installs the hello and hello-world snaps as a single transaction using the --transaction=all-snaps argument. The output shows both snaps installed successfully, but no change, log, or message indicates that the set was installed as a single transaction.

```bash
$ snap install hello hello-world --transaction=all-snaps
hello-world 6.4 from Canonical✓ installed
hello 2.10 from Canonical✓ installed

```

--------------------------------

### Install snap file with --name instance key

Source: https://snapcraft.io/docs/explanation/how-snaps-work/parallel-installs

Install a snap from a local .snap file with an explicit instance key. The --name flag sets the instance name (snap_instance) when installing from a file.

```bash
sudo snap install --name hello-world_foo hello-world_27.snap

```

--------------------------------

### Install an unpacked snap with snap try

Source: https://snapcraft.io/docs/how-to-guides/snap-development/snap-try

Installs an unpacked snap using a bind mount. The output shows the snap being mounted and the location of the installed command.

```bash
$ snap try squashfs-root
hello-world 6.4 mounted from /home/user/squashfs-root
$ which hello-world
/snap/bin/hello-world

```

--------------------------------

### GET request to /v2/apps with jq formatting

Source: https://snapcraft.io/docs/how-to-guides/snap-development/use-the-rest-api

This example sends a GET request to the /v2/apps endpoint and pipes the response through jq for formatting. The output shows a JSON object with type sync, status-code 200, and a result array containing snap details. Use this to retrieve and inspect the list of installed snaps.

```bash
$ sudo curl -sS --unix-socket /run/snapd.socket http://localhost/v2/apps \
| jq
{
  "type": "sync",
  "status-code": 200,
  "status": "OK",
  "result": [
    {
      "snap": "anbox-installer",
      "name": "anbox-installer"
    }
  ]
}

```

--------------------------------

### snapcraft edit-validation-sets example

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/manage-validation-sets

Example command using a sample account ID, set name 'myset1', and sequence 1. The sequence number starts at 1.

```bash
snapcraft edit-validation-sets xSfWKGdLoQBoQx88vIM1MpbFNMq53t1f myset1 1

```

--------------------------------

### snap install hello-world --revision 27

Source: https://snapcraft.io/docs/explanation/how-snaps-work/revisions

Installs revision 27 of the hello-world snap. The output confirms the installed revision.

```bash
$ snap install hello-world --revision 27
hello-world 6.3 from Canonical✓ installed

```

--------------------------------

### Install Snapcraft

Source: https://snapcraft.io/docs/snapcraft-overview

Installs Snapcraft as a snap with classic confinement.

```bash
snap install snapcraft --classic
```

--------------------------------

### Install snap from beta channel

Source: https://snapcraft.io/docs/explanation/how-snaps-work/channels-and-tracks

Installs VLC from the beta risk-level. If the beta snap is not available, the snap is installed from the closest channel with a more stable risk-level.

```bash
sudo snap install --channel=beta vlc

```

--------------------------------

### Install multiple snap instances with instance key

Source: https://snapcraft.io/docs/explanation/how-snaps-work/parallel-installs

Install two instances of the hello-world snap in one command. The second instance uses the instance key 'foo' appended with an underscore. Each instance is isolated from the others.

```bash
sudo snap install hello-world hello-world_foo

```

--------------------------------

### Install snapd on openSUSE

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/opensuse

Installs the snapd package using zypper.

```bash
sudo zypper install snapd

```

--------------------------------

### Start and enable a service

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/control-services

Starts a service and re-enables its automatic start on system boot.

```bash
snap start --enable lxd.daemon

```

--------------------------------

### Install Snapd from beta channel

Source: https://snapcraft.io/docs/reference/release-notes

Use this command to install Snapd from the beta channel. This is useful for testing beta releases.

```bash
sudo snap refresh snapd --beta
```

--------------------------------

### Install snapd with pacman

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/manjaro-linux

Installs the snapd package from the command line. Run this if snap is not already installed or has been removed.

```bash
sudo pacman -S snapd

```

--------------------------------

### Install components from local files with --dangerous flag

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/using-components

Installs components from a local file. Unasserted components can only be installed if the host snap is unasserted too, and the --dangerous flag is required.

```bash
snap install --dangerous ./my-snap+comp1+comp2_1.0.comp

```

--------------------------------

### snap info output with revision numbers

Source: https://snapcraft.io/docs/explanation/how-snaps-work/revisions

Example output of `snap info <snapname>` showing revision numbers in brackets after the publishing date for each channel. The installed revision appears on the final line.

```text
channels:
  latest/stable:    2.59.4                 2023-05-31 (19361) 55MB -
  latest/candidate: 2.59.5                 2023-06-09 (19457) 55MB -
  latest/beta:      2.59.5                 2023-05-27 (19457) 55MB -
  latest/edge:      2.59.5+git955.gc9310cc 2023-06-13 (19535) 42MB -
installed:          2.59.1+git798.g5f761c7            (19131) 42MB snapd

```

--------------------------------

### Install LXD

Source: https://snapcraft.io/docs/snapcraft-overview

Installs LXD, the build provider that containerizes the build environment.

```bash
snap install lxd
```

--------------------------------

### Install snapd from command line

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/linux-mint

Installs snapd via the command line as an alternative to using the Software Manager.

```bash
sudo apt install snapd
```

--------------------------------

### Enable snapd.apparmor.service for confinement

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/arch-linux

Enables and starts the AppArmor service for snap confinement. Requires AppArmor to be installed and enabled first.

```bash
sudo systemctl enable --now snapd.apparmor.service

```

--------------------------------

### Test changes to an unpacked snap

Source: https://snapcraft.io/docs/how-to-guides/snap-development/snap-try

Shows how changes to files in the squashfs-root directory are immediately reflected in the installed snap. The example edits the bin/echo script and runs the snap again to see the updated output.

```bash
$ hello-world
Hello world!
$ sed -i 's/World/Everyone/g' /home/user/squashfs-root/bin/echo
$ hello-world
Hello Everyone!

```

--------------------------------

### Connect personal-files plug with snap connect

Source: https://snapcraft.io/docs/reference/interfaces/personal-files-interface

Connects the dot-config-foo plug to enable access to the personal files declared in the snapcraft.yaml example. Use this command after the snap is installed to grant the snap access to the specified home directory files.

```shell
snap connect foo:dot-config-foo

```

--------------------------------

### Example snapcraft.yaml for hello-docker snap

Source: https://snapcraft.io/docs/reference/interfaces/docker-interface

Defines a strictly confined snap with the hello-docker app, using the docker and docker-executables plugs. The docker-executables plug is a content interface that requires an empty directory named docker-snap in the snap's image. The default-provider field ensures the docker snap is installed and connected automatically if not present.

```yaml
base: core22
confinement: strict
apps:
  hello-docker:
    command: usr/bin/hello-docker
    environment:
      PATH: $SNAP/docker-snap/bin:$PATH
    plugs:
      - docker
      - docker-executables
plugs:
  docker:
    label: Access to the docker communication socket
  docker-executables:
    label: Access to the docker command-line utilities
    interface: content
    content: docker-executables
    target: $SNAP/docker-snap
    default-provider: docker

```

--------------------------------

### snap list output with Rev column

Source: https://snapcraft.io/docs/explanation/how-snaps-work/revisions

Example output of `snap list` showing the `Rev` column with each installed snap's revision number.

```text
Name         Version  Rev    Tracking       Publisher             Notes
alacritty    0.8.0    46     latest/stable  snapcrafters✪         classic
blender      3.5.0    3486   latest/stable  blenderfoundation✓    classic
chromium     112.0    2424   latest/stable  canonical✓            -
ffmpeg       4.3.1    1286   latest/stable  snapcrafters✪         -

```

--------------------------------

### Install build dependencies

Source: https://snapcraft.io/docs/explanation/snap-development/building-snap-rpms-on-rhel

Refresh the package list and install the Go toolset and rpmdevtools, which are needed for building snap RPMs.

```bash
$ sudo dnf upgrade
$ sudo dnf module install go-toolset
$ sudo dnf install rpmdevtools

```

--------------------------------

### Declare network and network-bind plugs in snapcraft.yaml

Source: https://snapcraft.io/docs/reference/interfaces/network-interface

Example snapcraft.yaml configuration declaring the network plug for a client application and both network and network-bind plugs for a frontend server application. Both interfaces auto-connect on installation and require no additional store review.

```yaml
apps:
  client:
    command: bin/client-application
    plugs:
      - network
  frontend:
    command: bin/server-application
    plugs:
      - network
      - network-bind

```

--------------------------------

### fde-setup features operation example

Source: https://snapcraft.io/docs/reference/development/uc20-fde-hooks

Example of the fde-setup hook handling the "features" operation. The hook calls snapctl fde-setup-request, reads the JSON from stdout, and reports an empty features list via snapctl fde-setup-result.

```shell
$ snapctl fde-setup-request
{"op":"features"}

$ echo '{"features": []}' | snapctl fde-setup-result

```

--------------------------------

### Install snapd from AUR using git clone and makepkg

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/arch-linux

Manual build process for installing snap from the Arch User Repository. Requires the prerequisites for building AUR packages to be installed first.

```bash
git clone https://aur.archlinux.org/snapd.git
cd snapd
makepkg -si

```

--------------------------------

### Install snapd package

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/almalinux-os

Installs the snapd package from the EPEL repository. Requires root or sudo privileges.

```bash
sudo dnf install snapd

```

--------------------------------

### Example configure hook shell script

Source: https://snapcraft.io/docs/reference/development/supported-snap-hooks

Shell script for the configure hook that retrieves username and password via snapctl get, validates them, and writes credentials to $SNAP_DATA/options. Exits with non-zero status if required values are missing.

```sh
#!/bin/sh -e

username="$(snapctl get username)"
password="$(snapctl get password)"

if [ -z "$username" -o -z "$password" ]; then
    echo "Username and password are required."
    exit 1
fi

mkdir -m 0600 $SNAP_DATA/options
echo "username: $username" > $SNAP_DATA/options/credentials
echo "password: $password" >> $SNAP_DATA/options/credentials

```

--------------------------------

### Install snap from stable channel

Source: https://snapcraft.io/docs/explanation/how-snaps-work/channels-and-tracks

Installs VLC from the default stable risk-level. Use this command when you want the default stable release.

```bash
sudo snap install vlc

```

--------------------------------

### List all components with snap components

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/using-components

Lists the components installed and available on the system. The output shows the component name, status, and type.

```bash
$ snap components
Component                    Status     Type
snap-with-comps+one          installed  standard
snap-with-comps+two          installed  standard
snap-with-comps+three        available  standard
other-snap-with-comps+one    installed  standard
other-snap-with-comps+two    installed  standard
other-snap-with-comps+three  available  standard

```

--------------------------------

### snapctl get syntax

Source: https://snapcraft.io/docs/how-to-guides/snap-development/use-snapctl

Shows the basic syntax for querying a configuration option with snapctl get.

```bash
snapctl get <configuration option>
```

--------------------------------

### snap debug timings --verbose output

Source: https://snapcraft.io/docs/explanation/how-snaps-work/snap-performance

Example output from `snap debug timings --verbose` showing a label column for the change. The `--last` argument can be used with names like `auto-refresh`, `install`, `refresh`, `remove`, or `try`.

```text
ID     Status Doing  Undoing  Label          Summary
160162 Done   750ms        -  prerequisites  Ensure prerequisites for "chromium" are available
^             681ms        -  install-prereq install "cups"
```

--------------------------------

### Refresh snap and install component simultaneously

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/using-components

Refreshes the snap my-snap and installs the component comp1 at the same time.

```bash
snap refresh my-snap+comp1

```

--------------------------------

### Test snapd with hello-world

Source: https://snapcraft.io/docs/explanation/snap-development/building-snap-rpms-on-rhel

Test the snapd environment by installing the hello-world snap. A reboot/logout should put hello-world in the path.

```bash
$ snap install hello-world

```

--------------------------------

### Enable and start snapd service

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/opensuse

Enables and starts the snapd service. After this, reboot, logout/login, or source /etc/profile to add /snap/bin to PATH.

```bash
sudo systemctl enable --now snapd

```

--------------------------------

### Fetch sources and install build dependencies

Source: https://snapcraft.io/docs/explanation/snap-development/building-snap-rpms-on-rhel

Fetch remaining release packages and install build dependencies using the snapd spec file.

```bash
$ spectool -g ~/rpmbuild/SOURCES/snapd.spec
$ sudo dnf builddep ~/rpmbuild/SPECS/snapd.spec -y

```

--------------------------------

### Install snapd on Elementary OS

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/elementary-os

Run these commands in Terminal to update the package list and install snapd. After installation, log out and back in or restart to update snap's paths.

```bash
sudo apt update
sudo apt install snapd

```

--------------------------------

### Install and revert a test snapd build

Source: https://snapcraft.io/docs/how-to-guides/snap-development/test-snapd-fixes

Install a test snapd from a downloaded artifact: unzip the snap-files archive, install the resulting snap with --dangerous, and later revert to the stable channel with snap refresh --stable --amend.

```bash
$ unzip snap-files.zip
Archive:  snap-files.zip
  inflating: snapd_2.53.2+git6345be5.6345be5-dirty_amd64.snap

```

```bash
$ snap install --dangerous snapd_2.53.2+git6345be5.6345be5-dirty_amd64.snap
2021-11-24T13:06:46Z INFO Waiting for automatic snapd restart...
snapd 2.53.2+git6345be5.6345be5-dirty installed

```

```bash
$ snap refresh snapd --stable --amend

```

--------------------------------

### Example default-configure hook script

Source: https://snapcraft.io/docs/reference/development/supported-snap-hooks

A shell script for the default-configure hook. It retrieves a gadget option using snapctl get, applies a default value if unset, creates a directory with mode 0600, and writes the option to a file. The hook must be located in meta/hooks and requires a configure hook to be present.

```shell
#!/bin/sh -e

DEFAULT_GADGET_OPTION="123"

gadget_option="$(snapctl get gadget-option)"
if [ -z "$gadget_option" ]; then
gadget_option="$DEFAULT_GADGET_OPTION"
fi

mkdir -m 0600 $SNAP_DATA/options
echo "option: $gadget_option" > $SNAP_DATA/options/gadget

```

--------------------------------

### View component details with snap component

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/using-components

Displays information about an installed or available component. The installed: line is only printed if the component is installed.

```bash
$ snap component qwen-vl+llamacpp
component: qwen-vl+llamacpp
type: standard
summary: llama.cpp Engine using default CPU instruction sets
description: |
  LLM inference in C/C++
installed: b5794 (240) 30MB

```

--------------------------------

### Install snapd package

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/centos

Install the snapd package using yum after adding the EPEL repository.

```bash
sudo yum install snapd

```

--------------------------------

### Show component summary with snap info

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/using-components

Displays a summary of the ratio of installed components to available components. The summary is omitted if both installed and available components are zero.

```bash
$ snap info qwen-vl 
name:      qwen-vl
summary:   Qwen VL inference snap
...
installed:          2.5            (248) 332MB -
components: 4/14

```

--------------------------------

### Install strace-static snap

Source: https://snapcraft.io/docs/how-to-guides/snap-development/debug-snaps

Install the strace-static snap to enable running snaps under strace. Requires snapd 2.62.

```bash
sudo snap install strace-static

```

--------------------------------

### Install snap with --dangerous

Source: https://snapcraft.io/docs/snapcraft-overview

Installs the locally built snap with --dangerous because it is not from the Snap Store and thus not checked for safety.

```bash
snap install ukuzama-pyfiglet_0.1_amd64.snap --dangerous

```

--------------------------------

### Install snap-http Python package

Source: https://snapcraft.io/docs/how-to-guides/snap-development/use-the-rest-api

Install the snap-http Python package, which provides a Python interface to the snapd REST API. After installation, refer to the snap-http repository for documentation and usage examples.

```bash
pip install snap-http

```

--------------------------------

### Install Juju 2.9 and 3.0 in parallel with --channel

Source: https://snapcraft.io/docs/explanation/how-snaps-work/parallel-installs

Install two instances of Juju on different channels/tracks. Each instance is installed separately with its own channel and instance key (juju_29, juju_30). The --classic flag is used for both.

```bash
sudo snap install --channel 2.9/stable juju_29 --classic
sudo snap install --channel 3.0/stable juju_30 --classic

```

--------------------------------

### Build and serve live preview with make run

Source: https://snapcraft.io/docs/contributing/local-development

Builds and serves the documentation at http://127.0.0.1:8000/ with live reload on file changes. Use this command to start a local preview while editing.

```make
make run

```

--------------------------------

### Install snapd on Debian without sudo (as root)

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/debian

Use these commands when sudo is not installed, typically because a root password was provided at install time. Switch to the root account first.

```bash
$ su root
# apt update
# apt install snapd

```

--------------------------------

### Gadget YAML connections example

Source: https://snapcraft.io/docs/reference/development/yaml-schemas/the-gadget-snap

Example connections section in a gadget.yaml, listing plug and slot pairs for account-control, network-manager, and shell-config-files. Use to declare interface connections for the gadget snap.

```yaml
connections:
  - plug: LVkazk0JLrL0ivuHRlv3wp3bK1nAgwtN:account-control
  - plug: LVkazk0JLrL0ivuHRlv3wp3bK1nAgwtN:network-manager
    slot: RmBXKl6HO6YOC2DE4G2q1JzWImC04EUy:service
  - plug: LVkazk0JLrL0ivuHRlv3wp3bK1nAgwtN:shell-config-files
    slot: system:system-files
```

--------------------------------

### Install snap into quota group

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/use-resource-quotas

Installs a snap and adds it to an existing quota group.

```bash
snap install snap1 --quota-group=mygroup

```

--------------------------------

### Install snapd RPM packages

Source: https://snapcraft.io/docs/explanation/snap-development/building-snap-rpms-on-rhel

Install the three built RPM packages: snap-confine, snapd, and snapd-selinux.

```bash
$ sudo dnf localinstall \
   ~/rpmbuild/RPMS/x86_64/snap-confine-2.42-0.el8.x86_64.rpm \
   ~/rpmbuild/RPMS/x86_64/snapd-2.42-0.el8.x86_64.rpm \
   ~/rpmbuild/RPMS/noarch/snapd-selinux-2.42-0.el8.noarch.rpm

```

--------------------------------

### Enable and start snapd.apparmor service

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/opensuse

Enables and starts the snapd.apparmor service. Recommended to restart the machine after this step.

```bash
sudo systemctl enable --now snapd.apparmor

```

--------------------------------

### Initialize snap project with snapcraft init

Source: https://snapcraft.io/docs/snapcraft-overview

Runs the `snapcraft init` command to generate a template `snapcraft.yaml` file in the `snap/` directory.

```bash
snapcraft init

```

--------------------------------

### Simple snap.yaml with an app

Source: https://snapcraft.io/docs/reference/development/yaml-schemas/the-snap-format

An example snap.yaml that declares an application with a command.

```yaml
name: simple
version: 1.0
apps:
    hello:
        command: bin/hello --world

```

--------------------------------

### Static Netplan configuration example

Source: https://snapcraft.io/docs/reference/administration/system-options

Example of a static network configuration for the system.network.netplan key. Shows the structure with addresses, gateway4, and nameservers for the enp0s2 device. This is the configuration that the subsequent snap set command modifies.

```json
{
        "system.network.netplan": {
                "network": {
                        "ethernets": {
                                "enp0s2": {
                                        "addresses": [
                                                "10.0.2.15/24"
                                        ],
                                        "gateway4": "10.0.2.2",
                                        "nameservers": {
                                                "addresses": [
                                                        "8.8.8.8",
                                                        "8.8.4.4"
                                                ],
                                                "search": []
                                        }
                                }
                        },
                        "version": 2
                }
        }
}

```

--------------------------------

### Install font with -L

Source: https://snapcraft.io/docs/snapcraft-overview

Installs a font (Small Braille) from the figlet-fonts project.

```bash
ukuzama-pyfiglet -L smbraille.tlf

```

--------------------------------

### Install the snapd snap for latest features

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/debian

After installing snapd and restarting the system, install the snapd snap to get the latest snapd. Some snaps may require new snapd features and show an error like 'snap "lxd" assumes unsupported features' if not updated.

```bash
sudo snap install snapd

```

--------------------------------

### Configure polkit interface with action-prefix and install-rules

Source: https://snapcraft.io/docs/reference/interfaces/polkit-interface

Snapcraft YAML configuration for the polkit interface. Sets the action-prefix to org.example.foo and installs a polkit rule file named polkit.bar.rules with its sha3-384 hash. The app named 'app' runs command 'foo' and plugs into the polkit interface.

```yaml
plugs:
 polkit:
  action-prefix: org.example.foo
  install-rules:
      - name: polkit.bar.rules
        sha3-384: 2YM8oyXyE7xuXR07EXqUpixvr8duiJwgPQqhnxZgrBCU8ZSDowV0Gyujvs1j0-KR

apps:
 app:
  command: foo
  plugs: [polkit]

```

--------------------------------

### Install a snap in developer mode

Source: https://snapcraft.io/docs/how-to-guides/snap-development/debug-snaps

Install a snap with `--devmode` to permit security policy violations and log them via journald.

```bash
sudo snap install --devmode mysnap

```

--------------------------------

### Install secret-tool snap for testing

Source: https://snapcraft.io/docs/how-to-guides/snap-development/use-the-secret-portal

Install the secret-tool snap from the store using the appropriate track depending on the base you want to test. Replace XX with the base version (e.g., 22 for core22).

```bash
snap install secret-tool \--channel XX/stable to use coreXX base  

```

--------------------------------

### Install snappy-debug tool

Source: https://snapcraft.io/docs/how-to-guides/snap-development/debug-snaps

Install the snappy-debug tool, which watches syslog for policy violations and shows them in a human-readable format with recommendations.

```bash
sudo snap install snappy-debug

```

--------------------------------

### Enable experimental.parallel-instances feature flag

Source: https://snapcraft.io/docs/explanation/how-snaps-work/parallel-installs

Enable the experimental parallel-instances feature flag before attempting parallel installs. Without this, snap install fails if the same snap is already installed. Rebooting after toggling the flag is recommended to avoid namespace problems with already-run snap applications.

```bash
sudo snap set system experimental.parallel-instances=true

```

--------------------------------

### udev-tagging syntax example

Source: https://snapcraft.io/docs/reference/interfaces/custom-device-interface

Shows the udev-tagging syntax for the custom-device interface, mapping kernel, subsystem, and attributes to udev rules. The example uses two entries with different idVendor values.

```yaml
   udev-tagging:
     - kernel: hiddev0
       subsystem: usb
       attributes:
         idVendor: "0x03f0" # HP
     - kernel: hiddev1
       subsystem: usb
       attributes:
         idVendor: "0x03fc" # ECS

```

--------------------------------

### snapctl mount --persistent example

Source: https://snapcraft.io/docs/how-to-guides/snap-development/use-snapctl

Mount a persistent mount point with the `--persistent` option, using bind mount with read-write options. The example mounts /usr/share to /media/mount.

```bash
$ snapctl mount --persistent -o bind,rw /usr/share /media/mount

```

--------------------------------

### Basic timer examples

Source: https://snapcraft.io/docs/reference/administration/timer-string-format

Basic timer examples showing time ranges with frequency and a single time. Each line is a separate timer string with its own schedule.

```text
00:00-24:00/24
```

```text
00:00-24:00/48
```

```text
00:00-24:00/96
```

```text
12:00-13:00/12
```

```text
23:00
```

--------------------------------

### snap debug timings --startup=ifacemgr

Source: https://snapcraft.io/docs/explanation/how-snaps-work/snap-performance

Use the `--startup` argument with `snap debug timings` to output startup timing data for the `ifacemgr` subsystem. The output shows execution times for setting up security profiles for installed snaps before snapd becomes operational.

```bash
$ snap debug timings --startup=ifacemgr
ID        Status        Doing      Undoing  Summary
ifacemgr                    -            -  
 ^                        8ms            -    setup security backend "apparmor" for snap "core"
 ^                        7ms            -    setup security backend "mount" for snap "lxd"
 ^                       16ms            -    setup security backend "apparmor" for snap "lxd"
 ^                       12ms            -    load unchanged security profiles of snap "lxd"
 ^                        7ms            -    setup security backend "apparmor" for snap "vlc"
 ^                        5ms            -    load unchanged security profiles of snap "vlc"


```

--------------------------------

### Raspberry Pi gadget.yaml example

Source: https://snapcraft.io/docs/reference/development/yaml-schemas/the-gadget-snap

Example gadget.yaml for a Raspberry Pi, defining device-tree, volumes, and structures for ubuntu-seed, ubuntu-boot, ubuntu-save, and ubuntu-data. Includes comments about optional ubuntu-save and MBR partition limits.

```yaml
device-tree: bcm2709-rpi-3-b-plus
volumes:
  pi:
    schema: mbr
    bootloader: u-boot
    structure:
      - name: ubuntu-seed
        role: system-seed
        filesystem: vfat
        type: 0C
        size: 1200M
        content:
          - source: boot-assets/
            target: /
      - name: ubuntu-boot
        role: system-boot
        filesystem: vfat
        type: 0C
        # what's the appropriate size?
        size: 750M
        content:
          # TODO:install the boot.sel via snapd instead of via the gadget
          - source: boot.sel
            target: uboot/ubuntu/boot.sel
      # NOTE: ubuntu-save is optional for unencrypted devices like the pi, so
      # this structure can be dropped in favor of a different partition for
      # users who wish to instead use a different partition, since with MBR we
      # are limited to only 4 primary partitions.
      # TODO: look into switching over to GPT, the pi bootloader firmware now
      #       has support for this
      - name: ubuntu-save
        role: system-save
        filesystem: ext4
        type: 83,0FC63DAF-8483-4772-8E79-3D69D8477DE4
        size: 16M
      - name: ubuntu-data
        role: system-data
        filesystem: ext4
        type: 83,0FC63DAF-8483-4772-8E79-3D69D8477DE4
        # XXX: make auto-grow to partition
        size: 1500M
```

--------------------------------

### snap get nextcloud

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/configure-snaps

Displays the configuration options of an installed snap. The output shows the top-level keys and values, with {...} indicating nested options beneath the current key name level.

```shell
$ sudo snap get nextcloud
Key        Value
mode       production
nextcloud  {...}
php        {...}
ports      {...}
private    {...}

```

--------------------------------

### Register install hook with network plug in snapcraft.yaml

Source: https://snapcraft.io/docs/reference/development/supported-snap-hooks

Excerpt from snapcraft.yaml that registers an install hook using the network plug. Place this under the hooks key in the snapcraft.yaml file.

```yaml
apps:
    ...

hooks:
    install:
        plugs: [network]

```

--------------------------------

### Install and connect snaps for confdb access

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/configure-snaps-with-confdb

Install the custodian-snap and reader-snap snaps, then connect their confdb plugs to the network-wifi-admin and network-wifi-state views. When a snap is published by the same account ID as the assertion, the interface plug is auto-connected.

```bash
snap install custodian-snap reader-snap
snap connect custodian-snap:network-wifi-admin
snap connect custodian-snap:network-wifi-state
snap connect reader-snap:network-wifi-state

```

--------------------------------

### Enable and disable services with snapctl start/stop

Source: https://snapcraft.io/docs/how-to-guides/snap-development/use-snapctl

Enable a service with --enable when starting, and disable a service with --disable when stopping. Note the typo in the first command (myql instead of mysql).

```bash
$ snapctl start nextcloud.myql --enable
$ snapctl stop nextcloud.mysql --disable

```

--------------------------------

### Get system settings with snap get -d

Source: https://snapcraft.io/docs/reference/administration/system-options

Displays the current system settings, including the timezone. Available only on Ubuntu Core.

```bash
$ snap get -d system
{
        "experimental": {
                "hotplug": true,
                "layouts": true
        },
        "refresh": {
                "last": "2017-05-25T09:03:58.664837614+01:00",
                "retain": 2
        },
        "seed": {
                "loaded": true
        },
        "system": {
                "timezone": "America/Chicago"
        }
}

```

--------------------------------

### Install snapd on Rocky Linux

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/rocky-linux

Installs the snapd package from the EPEL repository on Rocky Linux. Requires EPEL to be added first.

```bash
$ sudo yum install snapd

```

--------------------------------

### Prepare RPM build environment

Source: https://snapcraft.io/docs/explanation/snap-development/building-snap-rpms-on-rhel

Set up the RPM build tree, download the snapd source tarball, and extract the RPM spec file into the SPECS directory.

```bash
$ rpmdev-setuptree
$ cd ~/rpmbuild/SOURCES
$ curl -L \
    https://github.com/canonical/snapd/releases/download/2.42/snapd_2.42.no-vendor.tar.xz \
    -o snapd_2.42.no-vendor.tar.xz
$ tar -xvJ -C ~/rpmbuild/SPECS --strip-components=3 \
    -f snapd_2.42.no-vendor.tar.xz \
    snapd-2.42/packaging/fedora/

```

--------------------------------

### squashfs mount error output

Source: https://snapcraft.io/docs/tutorials/install-the-daemon/fedora

Example error message that may appear when installing the first snap on a Fedora cloud image. Indicates the system does not fully support snapd due to missing squashfs support.

```text
error: system does not fully support snapd: cannot mount squashfs image using "squashfs": mount:
       /tmp/sanity-mountpoint-156693269: unknown filesystem type 'squashfs'.

```

--------------------------------

### View top-level system option categories and experimental options

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/set-system-options

Shows the output of 'snap get system' which lists top-level categories, and 'snap get system experimental' which displays the experimental options and their values.

```bash
$ snap get system
Key           Value
experimental  {...}
refresh       {...}
seed          {...}
system        {...}
$ snap get system experimental
Key                   Value
experimental.hotplug  true
experimental.layouts  true

```

--------------------------------

### Defining gpio plugs in snapcraft.yaml

Source: https://snapcraft.io/docs/reference/interfaces/gpio-interface

Example of defining distinct plugs for each GPIO pin in a snap's snapcraft.yaml, using the gpio interface.

```yaml
plugs:
  activity-led:
    interface: gpio
  warning-led:
    interface: gpio

```

--------------------------------

### Install a specific revision when a channel is closed

Source: https://snapcraft.io/docs/explanation/how-snaps-work/channels-and-tracks

Shows the output of installing a specific revision when the tracked channel is closed, and the revision list that explains why the snap appears to come from a riskier channel. The install command forwards to the edge channel because the requested revision is not available on the closed stable channel.

```shell
$ snap install hello-world --revision=28
hello-world (edge) 6.3 from Canonical✓ installed
Channel latest/stable for hello-world is closed; temporarily forwarding to edge.

```

```shell
$ snapcraft list-revisions hello-world
Rev.    Uploaded              Arches    Version    Channels
29      2019-04-17T16:43:58Z  all       6.4        latest/beta*,latest/candidate*,latest/edge*,latest/stable*
28      2017-11-20T07:59:46Z  all       6.3        latest/edge
27      2016-07-12T16:37:23Z  all       6.3        latest/beta,latest/candidate,latest/edge,latest/stable
26      2016-05-31T07:02:32Z  all       6.1        latest/edge,latest/stable
24      2016-04-19T15:37:06Z  all       6          latest/beta,latest/candidate,latest/edge,latest/stable

```

--------------------------------

### Install a classic snap with --classic

Source: https://snapcraft.io/docs/explanation/snap-development/install-modes

Required for classic snaps that need unfettered access to system resources. The --classic argument is silently accepted when installing a strict snap, but it won't change its confinement.

```bash
sudo snap install snapcraft --classic

```

--------------------------------

### prepare-serial hook: set registration.body with attestation data

Source: https://snapcraft.io/docs/reference/development/yaml-schemas/the-gadget-snap

Use in the optional prepare-serial hook to provide device attestation information during secure registration. It retrieves the registration request-id via snapctl get and sets registration.body with hardware identity fields. The hook runs after the gadget snap is installed when secure registration is required.

```shell
#!/bin/sh

# Get the request-id for registration
REQUEST_ID="$(snapctl get registration.request-id)"

# Sign request_id with HW ID private key

# set hardware identity attestation information
snapctl set registration.body="{\"hardware-id-key-sha3-384\": \"${HASH}\",
                                \"signature-hash-algorithm\": \"${SIG_HASH}\",
                                \"request-id-signature\": \"${SIGNATURE}\"
}"

```

--------------------------------

### List all snap services globally

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/control-services

Use `sudo snap services --global` to list all snap services for the entire system. Requires root-level access. Output shows service name, startup state, current state, and notes.

```bash
$ sudo snap services --global  
Service                    Startup  Current   Notes
lxd.activate               enabled  inactive  -
lxd.daemon                 enabled  active    socket-activated
lxd.user-daemon            enabled  inactive  socket-activated
multipass.multipassd       enabled  active    -
nextcloud.apache           enabled  active    -
nextcloud.logrotate        enabled  inactive  timer-activated
nextcloud.mysql            enabled  active    -
nextcloud.nextcloud-cron   enabled  active    -
nextcloud.nextcloud-fixer  enabled  active    -
nextcloud.php-fpm          enabled  active    -
nextcloud.redis-server     enabled  active    -
nextcloud.renew-certs      enabled  active    -

```

--------------------------------

### snap connections and disconnect/connect for instance

Source: https://snapcraft.io/docs/explanation/how-snaps-work/parallel-installs

Shows how to inspect and modify interface connections for a snap instance. The example lists connections, disconnects the network plug, verifies the slot becomes empty, reconnects, and shows the connection is now marked 'manual'.

```bash
$ snap connections xkcd-webserver_foo
Interface     Plug                             Slot           Notes
network       xkcd-webserver_foo:network       :network       -
network-bind  xkcd-webserver_foo:network-bind  :network-bind  -

$ sudo snap disconnect xkcd-webserver_foo:network

$ snap connections xkcd-webserver_foo
Interface     Plug                             Slot           Notes
network       xkcd-webserver_foo:network       -              -
network-bind  xkcd-webserver_foo:network-bind  :network-bind  -

$ sudo snap connect xkcd-webserver_foo:network

$ snap connections xkcd-webserver_foo
Interface     Plug                             Slot           Notes
network       xkcd-webserver_foo:network       :network       manual
network-bind  xkcd-webserver_foo:network-bind  :network-bind  -

```

--------------------------------

### Start an interactive shell during packaging with `snapcdd` --shell interactive shell. description: Run `sn_large.png

Source: https://snapcraft.io/docs/snapcraft-overview

Run `snapcraft pack --shell interactive shell inside the interactive shell. description: 

```bash_code
sn? Actually, exact code exactly as in source preserving whitespace preserving line breaks.actual code block content exactly as in source verbatim preserving whitespace and line breaks exactly as they appear.page_titleInspect the result: inspecting the build container and file structure. page_description: 
```

--------------------------------

### snap connections --all (with unconnected slots)

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/connect-interfaces

Lists all interfaces, including those without a connection. This is the same command as the first example but with a different output showing unconnected slots.

```bash
$ snap connections --all
Interface      Plug                    Slot                 Notes
adb-support    scrcpy:adb-support      :adb-support         -
alsa           entropypianotuner:alsa  -                    -
alsa           ffmpeg:alsa             :alsa                manual
alsa           guvcview:alsa           -                    -
(...)

```

--------------------------------

### Install Firefox from esr track

Source: https://snapcraft.io/docs/explanation/how-snaps-work/channels-and-tracks

Installs Firefox from the 'esr/stable' channel, which is a custom track. This command is used when you want to install a specific track of a snap.

```bash
snap install firefox --channel=esr/stable

```

--------------------------------

### Pack the snap with snapcraft pack

Source: https://snapcraft.io/docs/snapcraft-overview

Run the snapcraft pack command to build the snap. Downloading the container image can take a few minutes, but the build itself takes only a few seconds.

```bash
snapcraft pack

```

--------------------------------

### Set and get confdb data with snapctl and snap get

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/configure-snaps-with-confdb

Set data through the confdb view using snapctl set, then read it back with snapctl get and snap get. The change-view-network-wifi-admin hook is invoked when custodian-snap modifies the SSID, and the value is prefixed with 'acme'.

```bash
$ sudo snap run --shell custodian-snap.sh
# snapctl set --view :network-wifi-admin acme.ssid=some-ssid acme.password=super-secret
# exit

$ sudo snap run --shell reader-snap.sh
# snapctl get --view :network-wifi-state acme.ssid
acme-some-ssid
# exit

$ snap get <account-id>/network/wifi-state acme.ssid
acme-some-ssid

```

--------------------------------

### Build an unpacked snap with snapcraft try

Source: https://snapcraft.io/docs/how-to-guides/snap-development/snap-try

Builds a snap with snapcraft and exposes the prime directory for testing. The output shows the build process and the command to run snap try with the prime directory.

```bash
$ snapcraft try --use-lxd
Pulling hello-world
+ snapcraftctl pull
Building hello-world
+ snapcraftctl build
+ cp --archive --link --no-dereference . /root/parts/hello-world/install
Staging hello-world
+ snapcraftctl stage
Priming hello-world
+ snapcraftctl prime
You can now run `snap try /home/user/hello-world/prime`.

```

--------------------------------

### Command: ukuzama-pyfiglet -f thin hello, world!

Source: https://snapcraft.io/docs/snapcraft-overview

Run this command after repacking and reinstalling the snap to test the new fonts. The output shows the ASCII art generated with the thin font.

```bash
ukuzama-pyfiglet -f thin hello, world!
```

```text
|         |    |                                |        ||
|---.,---.|    |    ,---.        . . .,---.,---.|    ,---||
|   ||---'|    |    |   |        | | ||   ||    |    |   |
`   '`---'`---'`---'`---' |      `-'-'`---'`    `---'`---'o

```

--------------------------------

### Initialize LXD

Source: https://snapcraft.io/docs/snapcraft-overview

Initializes LXD with a lightweight, default configuration.

```bash
sudo lxd init --auto
```

--------------------------------

### Test a snapcraft prime directory with snap try

Source: https://snapcraft.io/docs/how-to-guides/snap-development/snap-try

Installs the prime directory produced by snapcraft try. The output shows the snap being mounted from the prime directory.

```bash
$ snap try /home/user/hello-world/prime
hello-world 0.1 mounted from /home/user/hello-world/prime

```

--------------------------------

### Run snap with font and show output

Source: https://snapcraft.io/docs/snapcraft-overview

Runs the snap with the installed font, omitting the .tlf extension, and shows the expected braille output.

```bash
ukuzama-pyfiglet -f smbraille hello, world!
⣇⡀ ⢀⡀ ⡇ ⡇ ⢀⡀    ⡀ ⢀ ⢀⡀ ⡀⣀ ⡇ ⢀⣸ ⡇
⠇⠸ ⠣⠭ ⠣ ⠣ ⠣⠜,   ⠱⠱⠃ ⠣⠜ ⠏  ⠣ ⠣⠼ ⠅

```

--------------------------------

### Enable pre-install disk space check with snap set

Source: https://snapcraft.io/docs/how-to-guides/manage-snaps/disk-space-awareness

Command to enable the experimental pre-install disk space check by setting system option `experimental.check-disk-space-install` to `true`.

```bash
snap set system experimental.check-disk-space-install=true
```