Configuration panel for apps

Configuration panels allow to let admins manage parameters or runs actions for which the upstream's app doesn't provide any appropriate UI itself. It's a good way to reduce manual change on config files and avoid conflicts on it.

Those panels can also be used to quickly create interfaces that extend the capabilities of YunoHost (e.g. VPN Client, Hotspost, Borg, etc.).

Please: Keep in mind the YunoHost spirit, and try to build your panels in such a way as to expose only really useful, "high-level" parameters, and if there are many of them, to relegate those corresponding to rarer use cases to "Advanced" sub-sections. Keep it simple, focus on common needs, don't expect the admins to have 3 PhDs in computer science.

config_panel.toml's principle and general format

To create configuration panels for apps, you should at least create a config_panel.toml at the root of the package. For more complex cases, this TOML file can be paired with a config script inside the scripts directory of your package, which will handle specific controller logic.

The config_panel.toml describes one or several panels, containing sections, each containing questions generally binded to a params in the app's actual configuration files.

Let's imagine that the upstream app is configured using this simple config.yml file stored in the app's install directory (typically /var/www/$app/config.yml):

title: 'My dummy app'
theme: 'white'
max_rate: 10
max_age: 365

We could for example create a simple configuration panel for it like this one, by following the syntax [PANEL.SECTION.QUESTION]:

version = "1.0"
[main]

    [main.main]
        [main.main.title]
        ask.en = "Title"
        type = "string"
        bind = ":__INSTALL_DIR__/config.yml"

        [main.main.theme]
        ask.en = "Theme"
        type = "select"
        choices = ["white", "dark"]
        bind = ":__INSTALL_DIR__/config.yml"

        [main.limits]
        [main.limits.max_rate]
        ask.en = "Maximum display rate"
        type = "number"
        bind = ":__INSTALL_DIR__/config.yml"

        [main.limits.max_age]
        ask.en = "Duration of a dummy"
        type = "number"
        bind = ":__INSTALL_DIR__/config.yml"

Here we have created one main panel, containing the main and limits sections, containing questions according to params name of our config.yml file. Thanks to the bind properties, all those questions are bind to their values in the config.yml file.

Questions short keys have to be unique

For performance reasons, questions short keys have to be unique in all the config_panel.toml file, not just inside its panel or its section. Hence it's not possible to have:

[manual.vpn.server_ip]
[advanced.dns.server_ip]

In which two questions have "real variable name" is server_ip and therefore conflict with each other.

Some short keys are forbidden cause it can interfer with config scripts (old, file_hash, types, binds, formats, changed) and you probably should avoid to use common settings name to avoid to bind your question to this settings (e.g. id, install_time, mysql_pwd, path, domain, port, db_name, current_revision, admin)

Supported questions types and properties

See the full list of questions types and properties

Reading and writing values

You can read and write values with 2 mechanisms: the bind property in the config_panel.toml and for complex use cases the getter/setter in a config script.

bind property

The bind property allows to define where read and write the value bind to the question.

Default behaviour

If you did not define a specific getter/setter (see below), and no bind argument was defined, YunoHost will read/write the value from/to the app's /etc/yunohost/apps/$app/settings.yml file.

Read / write into a var of an actual configuration file

If you want to read/write the value from/to the app's actual configural file (be it .env-like, JSON, YAML, INI, PHP, .py, ...):

[main.main.theme]
# (other properties ommited)
bind = ":__INSTALL_DIR__/config.yml"

In which case, YunoHost will look for something like a key/value, with the key being theme.

If the question id in the config panel (here, theme) differs from the key in the actual conf file (let's say it's not theme but css_theme), then you can write:

[main.main.theme]
# (other properties ommited)
bind = "css_theme:__FINALPATH__/config.yml"

Note: This mechanism is quasi language agnostic and will use regexes to find something that looks like a key=value or common variants. However, it does assume that the key and value are stored on the same line. It doesn't support multiline text or file in a variable with this method. If you need to save multiline content in a configuration variable, you should create a custom getter/setter (see below).

Nested syntax is also supported, which may be useful for example to remove ambiguities about stuff looking like:

{
    "foo": {
        "max": 123
    },
    "bar": {
        "max": 456
    }
}

which we can bind to using:

bind = "foo>max:__INSTALL_DIR__/conf.json"

Read / write an entire file

Useful when using a question file or text for which you want to save the raw content directly as a file on the system.

[main.main.logo]
# (other properties ommited)
bind = "__INSTALL_DIR__/img/logo.png"

Custom getter / setter

Sometimes the bind mechanism is not enough:

  • the config file format is not supported (e.g. xml, csv)
  • the data is not contained in a config file (e.g. database, directory, web resources...)
  • the data should be written but not read (e.g. password)
  • the data should be read but not written (e.g. fetching status information)
  • we want to change other things than the value (e.g. the choices list of a select)
  • the question answer contains several values to dispatch in several places
  • and so on

You can create specific getter/setters functions inside the scripts/config of your app to customize how the information is read/written.

#!/bin/bash
source /usr/share/yunohost/helpers

ynh_abort_if_errors

# Put your getter, setter and validator here

# Keep this last line
ynh_app_config_run $1

Getter

A question's getter is the function used to read the current value/state. Custom getters are defined using bash functions called getter__QUESTION_SHORT_KEY() which returns data through stdout.

Stdout can generated using one of those formats:

1) either a raw format, in which case the return is binded directly to the value of the question 2) or a yaml format, in this case you dynamically provide properties for your question (for example the style of an alert, the list of available choices of a select, etc.)

Basic example with raw stdout: get the timezone on the system

config_panel.toml

[main.main.timezone]
ask = "Timezone"
type = "string"

scripts/config

get__timezone() {
    echo "$(cat /etc/timezone)"
}
Basic example with yaml-formated stdout : Display a list of available plugins

config_panel.toml

        [main.plugins.plugins]
        ask = "Plugin to activate"
        type = "tags"
        choices = []

scripts/config

get__plugins() {
    echo "choices: [$(ls $install_dir/plugins/ | tr '\n' ',')]"
}
Advanced example with yaml-formated stdout : Display the status of a VPN

config_panel.toml

        [main.cube.status]
        ask = "Custom getter alert"
        type = "alert"
        style = "info"
        bind = "null" # no behaviour on

scripts/config

get__status() {
    if [ -f "/sys/class/net/tun0/operstate" ] && [ "$(cat /sys/class/net/tun0/operstate)" == "up" ]
    then
    cat << EOF
style: success
ask:
  en: Your VPN is running :)
EOF
    else
    cat << EOF
style: danger
ask:
  en: Your VPN is down
EOF
    fi
}

Setter

A question's setter is the function used to set new value/state. Custom setters are defined using bash functions called setter__QUESTION_SHORT_KEY(). In the context of the setter function, variables named with the various quetion's short keys are avaible ... for example the user-specified date for question [main.main.theme] is available as $theme.

When doing non-trivial operations to set a value, you may want to use ynh_print_info to inform the admin about what's going on.

Basic example : Set the system timezone

config_panel.toml

[main.main.timezone]
ask = "Timezone"
type = "string"

scripts/config

set__timezone() {
    echo "$timezone" > /etc/timezone
    ynh_print_info "The timezone has been changed to $timezone"
}

Validation

You will often need to validate data answered by the user before to save it somewhere.

Validation can be made with regex through pattern argument

        pattern.regexp = '^.+@.+$'
        pattern.error = 'An email is required for this field'

You can also restrict several types with a choices list.

        choices.foo = "Foo (some explanation)"
        choices.bar = "Bar (moar explanation)"
        choices.loremipsum = "Lorem Ipsum Dolor Sit Amet"
Some other type specific argument exist like type validation arguments
number, range min, max, step
file accept
boolean yes no

Finally, if you need specific or multi variable validation, you can use custom validators function:

validate__login_user() {
    if [[ "${#login_user}" -lt 4 ]]; then echo 'User login is too short, should be at least 4 chars'; fi
}

Other actions than read, validate and save

Restart a service at the end

You can use the services key to specify which service need to be reloaded or restarted.

services = [ 'nginx', '__APP__' ]

This argument can be set on a single question, to a section, or to an entire panel.

Overwrite config panel mechanism

All main configuration helpers are overwritable, example:

ynh_app_config_apply() {

    # Stop vpn client
    touch /tmp/.ynh-vpnclient-stopped
    systemctl stop ynh-vpnclient

    _ynh_app_config_apply

    # Start vpn client
    systemctl start ynh-vpnclient
    rm -f /tmp/.ynh-vpnclient-stopped

}

List of main configuration helpers

  • ynh_app_config_get
  • ynh_app_config_show
  • ynh_app_config_validate
  • ynh_app_config_apply
  • ynh_app_config_run

More info on this can be found by reading vpnclient_ynh config script

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