Update cheatsheets

tldr/linux/certtool

@@ -0,0 +1,29 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# certtool
+
+> Generate and manage X.509 certificates, keys, and PKI structures using GnuTLS.
+> More information: <https://gnutls.org/manual/gnutls.html#certtool-Invocation>.
+
+- Generate a private key and save it to a file:
+
+`certtool {{[-p|--generate-privkey]}} --outfile {{path/to/private.key}}`
+
+- Generate a self-signed certificate using a private key and a template file:
+
+`certtool {{[-s|--generate-self-signed]}} --load-privkey {{path/to/private.key}} --template {{path/to/info.template}} --outfile {{path/to/certificate.crt}}`
+
+- Generate a certificate signing request (CSR):
+
+`certtool {{[-q|--generate-request]}} --load-privkey {{path/to/private.key}} --template {{path/to/info.template}} --outfile {{path/to/request.csr}}`
+
+- Generate a certificate authority (CA) certificate:
+
+`certtool {{[-s|--generate-self-signed]}} --load-privkey {{path/to/ca.key}} --template {{path/to/ca.template}} --outfile {{path/to/ca.crt}}`
+
+- Verify a certificate against a CA certificate:
+
+`certtool --verify --infile {{path/to/certificate.crt}} --load-ca-certificate {{path/to/ca.crt}}`