Drophost

Drophost is a simple maintaining tool for your /etc/hosts file. It allows you to easily configure your hosts file dynamically using a drop-in directory.

Installation

Using Cargo

cargo install drophost

Arch Linux (AUR)

yay -S drophost

Install from source

Download the source code from github and build it using cargo.

git clone https://github.com/KodiCraft/drophost.git
cd drophost
cargo build --release

Or use cargo install

git clone https://github.com/KodiCraft/drophost.git
cd drophost
cargo install --path .

Usage

Backup your current system hosts file

drophost comes with the ability of saving your current /etc/hosts file as a configuration file. This way, your current hosts file will automatically be used when you run drophost.

sudo drophost -b

This file will be named 10-old-config.conf and will be located in the drop-in directory.

Adding your own files

drophost will read files out of the /etc/hosts.d directory. Any files in the directory will be read and parsed. The files are read in alphabetical order, so you can use numbers to control the order in which they are read.

If you would like to test out your files, create a directory named output and treat it like your /etc/ directory (i.e. add your configuration files to output/hosts.d and read the result from output/hosts). Then run drophost with the -d flag.

drophost -d

Flags

Drophost comes with a few flags that can be used to customize its behavior.

• -b or --backup will backup your current hosts file to the drop-in directory.
• -d or --dry-run will run drophost without modifying your hosts file.
• -w or --watch will watch the drop-in directory for changes and automatically update your hosts file when a change is detected.
• -h or --help will display the help message.

You may also pass the -l or --log-level flag to set the log level. The default log level is info. The available log levels are trace, debug, info, warn, error, and off.

File format

Files for drophost are fully compatible with the syntax of the /etc/hosts file, but they do add some additional features.

As a reminder, hosts can be added with the following syntax:

ip.address hostname

And comments can be inserted with the # character.

# This is a comment

Loud comments

Loud comments are comments that will display a warning in the logs when they are encountered. This allows you to debug your configuration files easily.

#=> This is a loud comment

Variables

drophost allows you to define variables in your configuration file and fetch them later. You can set a variable with the following syntax:

set variable_name = value

You can then fetch the value of a variable with the following syntax:

$variable_name

Variables can be used practically everywhere in your configuration file. For example, you can use them to define a hostname:

set hostname = my-hostname
127.0.0.1 $hostname

Or to define an IP address:

set ip = 127.0.0.1
$ip my-hostname

You can also unset variables with the following syntax:

unset variable_name

Variables are maintained between different configuration files. This means that you can define a variable in one file and use it in another.

Additionally, all environment variables that drophost is called with are automatically available as variables. For example, if you call drophost with the HOSTNAME environment variable set to my-hostname, you can use it in your configuration file:

127.0.0.1 $env_HOSTNAME

Conditionals

Conditionals allow you to include branching logic in your configuration files. They are defined with the following syntax:

if $value1 == $value2
    # Do something
else
    # Do something else
end

The if statement will evaluate the condition and execute the block if the condition is true. If the condition is false, the else block will be executed. If no else block is defined, the if block will be executed if the condition is true.

You may use variables or literal values in the condition. For example, you can use the following syntax to check if a variable isn't equal to "hello world":

if $variable != hello world
    # Do something
end

Note how there aren't any quotes, spaces are allowed in variable names and in literal values.

Since all variables are strings, you only have the == and != operators available.

External conditions

Sometimes it can be useful to check if certain states are met that are not related to drophost's logic. This is where the try syntax comes in handy.

You can try any of the following conditions:

• file <path>: Checks if a file exists at the given path.
• var <name>: Checks if a variable is defined. Variables can be an empty string and be considered "defined"
• has <hostname>: Checks if a hostname has been previously defined.

Additionally, if you compile the project with the ping feature, you can also try the following condition:

• ping <hostname>: Checks if a hostname is reachable.

The releases in the Github Actions tab are never compiled with additional features!

The try syntax is defined as follows:

try <condition> <argument>
    # Do something
else
    # Do something else
end

The try statement will evaluate the condition and execute the block if the condition is true. If the condition is false, the else block will be executed. If no else block is defined, the try block will be executed if the condition is true.

License

This project is licensed under the MIT license. See the LICENSE file for more details.

Contributing

Help is always welcome! If you find a bug or have an idea for a new feature, please open an issue. If you want to contribute code, please open a pull request.

Make sure to write new tests for your code if it adds any new functionality! If you're not sure how to do that, feel free to ask for help.