What Is "openssl" Command

PKI Certificate Tutorials - Herong's Tutorial Examples

∟What Is "openssl" Command

This section describes the 'openssl' command, which invokes the OpenSSL CLI to access OpenSSL functions.

What Is "openssl" Command? "openssl" is the command to invoke the OpenSSL CLI (Command Line Interface) to access OpenSSL functions.

If the "openssl" command is not available on your computer, you can download and install the OpenSSL package. Here is what I did on my CentOS computer:

herong$ sudo dnf install openssl 

...
Installed:
  openssl-1:1.1.1k-5.el8_5.x86_64

The syntax to invoke the "openssl" command can be described as:

openssl command opts args 

Where: 
  command - one of 110 commands provided in OpenSSL 
  opts - list of options supported by the given command 
  args - list of arguments to feed into the given command

For example, the following command line invokes OpenSSL "x509" command with 1 option "-help" and no argument.

herong$ openssl x509 -help 

Usage: x509 [options]

General options:
  -help         Display this summary
  -in infile    Certificate input, or CSR input file with -req
  -passin val   Private key and cert file pass-phrase source
  ...

For more information on the "openssl" command, run the "man openssl" command:

herong$ man openssl

NAME
  openssl - OpenSSL command line tool

SYNOPSIS
  openssl command [ command_opts ] [ command_args ]
  openssl list [ standard-commands | digest-commands | cipher-...
  openssl no-XXX [ arbitrary options ]

DESCRIPTION
  OpenSSL is a cryptography toolkit implementing the Secure Sockets 
  Layer (SSL v2/v3) and Transport Layer Security (TLS v1) network 
  protocols and related cryptography standards required by them.

...