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C_REHASH(1SSL)                               OpenSSL                               C_REHASH(1SSL)

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

SYNOPSIS
       c_rehash [-old] [-h] [-n] [-v] [ directory...]

DESCRIPTION
       c_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 utility 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 shold 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 it will be skipped.  The links created are of the form "HHHHHHHH.D",
       where each H is a hexadecimal character and D is a single decimal digit.  When processing
       a directory, c_rehash will first remove all links that have a name in that syntax. If you
       have links in that format used for other purposes, they will be removed.  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.

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

       -h  Display a brief usage message.

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

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

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), crl(1).  x509(1).

1.0.2g                                      2016-03-01                             C_REHASH(1SSL)

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