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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]
       [-propquery propq] [directory] ...

       c_rehash [-h] [-help] [-old] [-n] [-v] [-provider name] [-provider-path path] [-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
       -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 2015-2020 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 <https://www.openssl.org/source/license.html>.



3.0.2                                        2026-04-07                         OPENSSL-REHASH(1SSL)