Manual: openssl-rehash

OPENSSL-REHASH(1SSL)					   OpenSSL					OPENSSL-REHASH(1SSL)

NAME
       openssl-rehash, c_rehash - Create symbolic links to files named by the hash values

SYNOPSIS
       openssl rehash [-h] [-help] [-old] [-compat] [-n] [-v] [-provider name] [-provider-path path] [-provparam
       [name:]key=value] [-propquery propq] [directory] ...

       c_rehash [-h] [-help] [-old] [-n] [-v] [-provider name] [-provider-path path] [-provparam [name:]key=value]
       [-propquery propq] [directory] ...

DESCRIPTION
       This command is generally equivalent to the external script c_rehash, except for minor differences noted below.

       openssl rehash scans directories and calculates a hash value of each .pem, .crt, .cer, or .crl file in the specified
       directory list and creates symbolic links for each file, where the name of the link is the hash value.  (If the
       platform does not support symbolic links, a copy is made.)  This command is useful as many programs that use OpenSSL
       require directories to be set up like this in order to find certificates.

       If any directories are named on the command line, then those are processed in turn. If not, then the SSL_CERT_DIR
       environment variable is consulted; this should be a colon-separated list of directories, like the Unix PATH variable.
       If that is not set then the default directory (installation-specific but often /usr/local/ssl/certs) is processed.

       In order for a directory to be processed, the user must have write permissions on that directory, otherwise an error
       will be generated.

       The links created are of the form HHHHHHHH.D, where each H is a hexadecimal character and D is a single decimal
       digit.  When a directory is processed, all links in it that have a name in that syntax are first removed, even if
       they are being used for some other purpose.  To skip the removal step, use the -n flag.	Hashes for CRL's look
       similar except the letter r appears after the period, like this: HHHHHHHH.rD.

       Multiple objects may have the same hash; they will be indicated by incrementing the D value. Duplicates are found by
       comparing the full SHA-1 fingerprint. A warning will be displayed if a duplicate is found.

       A warning will also be displayed if there are files that cannot be parsed as either a certificate or a CRL or if more
       than one such object appears in the file.

   Script Configuration
       The c_rehash script uses the openssl program to compute the hashes and fingerprints. If not found in the user's PATH,
       then set the OPENSSL environment variable to the full pathname.	Any program can be used, it will be invoked as
       follows for either a certificate or CRL:

	 $OPENSSL x509 -hash -fingerprint -noout -in FILENAME
	 $OPENSSL crl -hash -fingerprint -noout -in FILENAME

       where FILENAME is the filename. It must output the hash of the file on the first line, and the fingerprint on the
       second, optionally prefixed with some text and an equals sign.

OPTIONS
       -help -h
	   Display a brief usage message.

       -old
	   Use old-style hashing (MD5, as opposed to SHA-1) for generating links to be used for releases before 1.0.0.	Note
	   that current versions will not use the old style.

       -n  Do not remove existing links.  This is needed when keeping new and old-style links in the same directory.

       -compat
	   Generate  links  for both old-style (MD5) and new-style (SHA1) hashing.  This allows releases before 1.0.0 to use
	   these links along-side newer releases.

       -v  Print messages about old links removed and new links created.  By default, this command only lists each directory
	   as it is processed.

       -provider name
       -provider-path path
       -provparam [name:]key=value
       -propquery propq
	   See "Provider Options" in openssl(1), provider(7), and property(7).

ENVIRONMENT
       OPENSSL
	   The path to an executable to use to generate hashes and fingerprints (see above).

       SSL_CERT_DIR
	   Colon separated list of directories to operate on.  Ignored if directories are listed on the command line.

SEE ALSO
       openssl(1), openssl-crl(1), openssl-x509(1)

COPYRIGHT
       Copyright 2015-2025 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this  file  except  in  compliance  with	 the
       License.	    You	   can	  obtain   a   copy   in   the	 file	LICENSE	  in   the   source   distribution   or	  at
       .

3.5.5							 2026-01-27					OPENSSL-REHASH(1SSL)