<a href="https://github.com/lukas2511/letsencrypt.sh" rel="nofollow">https://github.com/lukas2511/letsencrypt.sh</a> provides a BASH script that only uses OpenSSL/cURL and similar tools to retrieve LetsEncrypt certificates. It also provides support for the dns-01 ACME challenge (which quite handily lets a certificate be requested and retrieved without having to write files anywhere, only requiring a DNS TXT record). To handle different DNS provider APIs, letsencrypt.sh delegates the DNS operations to a hook script: this little Go program implements the hook command line interface and uses the Linode DNS API to create/destroy the required TXT records. More info is available from the project README at <a href="https://github.com/IdeaSynthesis/letsencrypt-dns01-hooks/blob/master/README.md" rel="nofollow">https://github.com/IdeaSynthesis/letsencrypt-dns01-hooks/blo...</a> .