Hostsmod - safely modify /etc/hosts

Command line tool for modifying hosts file on Linux/UNIX to change static hostname-IP mappings.

Intended to be run with the suid bit set, so unprivileged users may update the hosts file. This allow easy integration for jobs like updating entries after launching a docker container or locally testing virtual hosts vor web projects without any requirement for privilege escalation.

Engineered for Safety

The tool has been engineered for safety and features a configurable list of hostnames for which entries may be modified. No other modifications are allowed.

Also, some key entries that might affect correct function of software like localhost are checked before writing the new configuration.

The new configuration is written to the file system under a different name next to the original file and only moved into place as the last step. This makes the change atomic (according to POSIX semantics) and any error occurring earlier leaves the existing configuration intact. After an unsuccessful run, if the new placeholder file is already present, manual intervention will be necessary.

Configuration

Run with --sample-config to generate a sample YAML config which can be placed at /etc/hostsmod.yaml. Take care to make this file only modifiable (or even accessible) to the root user if arbitrary modifications should be prohibited. The executable then has to be granted the suid bit, which can be done by sudo chmod u+s <path-to-hostsmod> and has to be owned by the root user.

Examples

Run with --help to get an extensive description of what the software does and how it is controlled.

Remove entry so the deployed instance can be accessed (observe -- to differentiate from flags):

hostsmod -- -prod.project.tld

Add entries so a local dev environment can be tested using real-world hostnames:

hostsmod -- 127.0.0.1=prod.project.tld ::1+=prod.project.tld 127.0.0.1=assets.project.tld

Add entry for random IP of temporary dev system:

hostsmod "$(docker inspect --format '{{ .NetworkSettings.Networks.svc.IPAddress }}' localdb)=database"