htdbm [ -TDBTYPE ] [ -i ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ]
[ -t ] [ -v ] filename username
htdbm -b [ -TDBTYPE ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [
-t ] [ -v ] filename username password
htdbm -n [ -i ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [ -t ] [
-v ] username
htdbm -nb [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [ -t ] [ -v ]
htdbm -v [ -TDBTYPE ] [ -i ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C
cost ] [ -t ] [ -v ] filename username
htdbm -vb [ -TDBTYPE ] [ -c ] [ -m | -B | -d | -s | -p ] [ -C cost ] [
-t ] [ -v ] filename username password
htdbm -x [ -TDBTYPE ] filename username
htdbm -l [ -TDBTYPE ]
htdbm is used to manipulate the DBM format files used to store user-
names and password for basic authentication of HTTP users via
mod_authn_dbm. See the dbmmanage documentation for more information
about these DBM files.
-b Use batch mode; i.e., get the password from the command line
rather than prompting for it. This option should be used with
extreme care, since the password is clearly visible on the com-
mand line. For script use see the -i option.
-i Read the password from stdin without verification (for script
-c Create the passwdfile. If passwdfile already exists, it is
rewritten and truncated. This option cannot be combined with the
-n Display the results on standard output rather than updating a
database. This option changes the syntax of the command line,
since the passwdfile argument (usually the first one) is omit-
ted. It cannot be combined with the -c option.
-m Use MD5 encryption for passwords. On Windows and Netware, this
is the default.
-B Use bcrypt encryption for passwords. This is currently consid-
ered to be very secure.
-C This flag is only allowed in combination with -B (bcrypt encryp-
tion). It sets the computing time used for the bcrypt algorithm
-p Use plaintext passwords. Though htdbm will support creation on
all platforms, the httpd daemon will only accept plain text
passwords on Windows and Netware.
-l Print each of the usernames and comments from the database on
-v Verify the username and password. The program will print a mes-
sage indicating whether the supplied password is valid. If the
password is invalid, the program exits with error code 3.
-x Delete user. If the username exists in the specified DBM file,
it will be deleted.
-t Interpret the final parameter as a comment. When this option is
specified, an additional string can be appended to the command
line; this string will be stored in the "Comment" field of the
database, associated with the specified username.
The filename of the DBM format file. Usually without the exten-
sion .db, .pag, or .dir. If -c is given, the DBM file is created
if it does not already exist, or updated if it does exist.
The username to create or update in passwdfile. If username does
not exist in this file, an entry is added. If it does exist, the
password is changed.
The plaintext password to be encrypted and stored in the DBM
file. Used only with the -b flag.
Type of DBM file (SDBM, GDBM, DB, or "default").
One should be aware that there are a number of different DBM file for-
mats in existence, and with all likelihood, libraries for more than one
format may exist on your system. The three primary examples are SDBM,
NDBM, GNU GDBM, and Berkeley/Sleepycat DB 2/3/4. Unfortunately, all
these libraries use different file formats, and you must make sure that
the file format used by filename is the same format that htdbm expects
to see. htdbm currently has no way of determining what type of DBM file
it is looking at. If used against the wrong format, will simply return
nothing, or may create a different DBM file with a different name, or
at worst, it may corrupt the DBM file if you were attempting to write
One can usually use the file program supplied with most Unix systems to
see what format a DBM file is in.
htdbm returns a zero status ("true") if the username and password have
Adds or modifies the password for user jsmith. The user is prompted for
the password. If executed on a Windows system, the password will be
encrypted using the modified Apache MD5 algorithm; otherwise, the sys-
tem's crypt() routine will be used. If the file does not exist, htdbm
will do nothing except return an error.
htdbm -c /home/doe/public_html/.htdbm jane
Creates a new file and stores a record in it for user jane. The user is
prompted for the password. If the file exists and cannot be read, or
cannot be written, it is not altered and htdbm will display a message
and return an error status.
htdbm -mb /usr/web/.htdbm-all jones Pwd4Steve
Encrypts the password from the command line (Pwd4Steve) using the MD5
algorithm, and stores it in the specified file.
Web password files such as those managed by htdbm should not be within
the Web server's URI space -- that is, they should not be fetchable
with a browser.
The use of the -b option is discouraged, since when it is used the
unencrypted password appears on the command line.
When using the crypt() algorithm, note that only the first 8 characters
of the password are used to form the password. If the supplied password
is longer, the extra characters will be silently discarded.
The SHA encryption format does not use salting: for a given password,
there is only one encrypted representation. The crypt() and MD5 formats
permute the representation by prepending a random salt string, to make
dictionary attacks against the passwords more difficult.
The SHA and crypt() formats are insecure by today's standards.
On the Windows platform, passwords encrypted with htdbm are limited to
no more than 255 characters in length. Longer passwords will be trun-
cated to 255 characters.
The MD5 algorithm used by htdbm is specific to the Apache software;
passwords encrypted using it will not be usable with other Web servers.
Usernames are limited to 255 bytes and may not include the character :.
Apache HTTP Server 2012-12-12 HTDBM(1)
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