DACSVFS(1) DACS Tools and Utilities DACSVFS(1)


dacsvfs — access objects through the DACS virtual filestore


dacsvfs [dacsoptions] [ item_type | vfs_uri | enabled ] [-F sep] [op [arg...]]


This program is part of the DACS suite.

The dacsvfs utility is an interface to the DACS virtual filestore. It provides a way to examine, change, and delete items independently of how and where they are stored. See dacs.vfs(5) and the VFS directive for additional information.

To perform a virtual filestore operation, either an item_type or a URI argument must be provided to identify the filestore. The former is used to find the applicable VFS directive that has been configured for the specified jurisdiction (see dacs.conf(5)).

As a special case, the word enabled can be specified; a list of enabled store names is printed to stdout and the program terminates:

% dacsvfs -q -uj SomeJurisdiction enabled

This program is also available as a DACS web service, dacs_vfs(8).


Only the DACS administrator should be able to successfully run this program. Because DACS keys and configuration files must be limited to the administrator, this will normally be the case, but a careful administrator will deny access to all other users.


-F sep

Sets the field separator character to sep. The default is a colon. This is used by the load and dump operations.

If present, the op argument specifies the operation to be performed on the filestore. If it is omitted, the program enters interactive mode where most of the same operations are available (type "help" for assistance). The following operations are available:

delete [key]

Delete the item, or the item identified by key.


Write to stdout the contents of the filestore as key, followed by the field separator character, followed by value, one pair per line.

edit [key]

Interactively edit the item, or the value of the item identified by key. When available, the environment variable EDITOR is used to determine which editor to use, otherwise a default editor specified at compile time is used. After editing, the user is asked for confirmation. If the operation is not aborted, the item or its value will be updated.

exists [key]

Test if the item, or the item identified by key, exists. The outcome is reported to stdout.

get [key]

Retrieve the item, or the value of the item identified by key. If successful, the result is printed to stdout.

getsize [key]

Determine the size of the item, or the size of the value of the item identified by key. If successful, the result is printed to stdout.


Prints a usage summary to stderr.


Lists the names of all items (or keys) associated with the item_type.


Read key/value pairs from stdin, one pair per line. The end of the key is denoted by the field separator character, which may be repeated. Whitespace may appear on either side of the field separator character (unless the field separator is a whitespace character). For each key do a put operation with the specified value. This is intended to be a quick way to initialize a filestore or make many changes.

put [key]

Replace the item, or the value of the item identified by key. The value is read from the standard input.

putval key value

Replace the item, or the value of the item identified by key, and set it to value.

rename [oldkey] newkey

Rename the item, or the value of the item identified by oldkey to newkey.

update [key]

This is a synonym for the edit operation.


To store the DTDs used by DACS in a database rather than in a collection of files, you must configure an appropriate VFS directive and copy the files from the DACS distribution into the database. Because it is read-only, this database can be shared by all federations and jurisdictions on the host.

The first step is to select the type of database to use and decide where to put it. This example will use a Berkeley DB database (DACS must have been built with support for whichever database is used) and put it in /usr/local/dacs/federations/dtds.db. The URI to express this in the VFS syntax looks like this:


The next step is to create the database and load it with the DTDs. A simple shell script makes this easy to do. From the dtd-xsd directory of the DACS distribution, and replacing example.com with the URI of a DACS jurisdiction on your host, execute:

#! /bin/sh

for i in *.dtd
  dacsvfs -u example.com -q \
      '[dtds]dacs-db:/usr/local/dacs/federations/dtds.db' put $i < $i

To configure DACS to use the database, a VFS directive must be put in an appropriate place in dacs.conf so that it overrides the current configuration:

VFS "[dtds]dacs-db:/usr/local/dacs/federations/dtds.db"

To list the contents of the database you can do:

% dacsvfs -u example.com -q \
    '[dtds]dacs-db:/usr/local/dacs/federations/dtds.db' list

or since the VFS directive has been configured, simply:

% dacsvfs -u example.com -q dtds list

If you omit the -q flag, various debugging output will appear, including some feedback that your new database is actually being used by DACS.


If you copy any DACS resources, such as its DTDs, remember that when you upgrade your DACS software you'll need to make new copies because these resources may have changed.

Other resources used by DACS would be configured similarly. The load and dump operations can be particularly useful for this. If the file /tmp/roles associates roles with identities (e.g., as used by dacscheck(1)) as follows:


then the following command initializes or updates a database from that file:

% dacsvfs -u example.com -q -F ":" \
    '[myroles]dacs-db:/usr/local/myapp/roles.db' < /tmp/roles

The URI [myroles]dacs-db:/usr/local/myapp/roles.db can then be used with dacscheck.


The program exits 0 if everything was fine, 1 if an error occurred.


There should be a caching mechanism that could be used with expensive storage types (i.e., those that are relatively slow to access, such as the http scheme).


dacs_vfs(8), dacs.conf(5)


Distributed Systems Software (www.dss.ca)


Copyright 2003-2018 Distributed Systems Software. See the LICENSE file that accompanies the distribution for licensing information.

DACS Version 1.4.50 21-Jul-2023 DACSVFS(1)

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$Id: dacsvfs.1.xml 3016 2018-08-17 18:12:46Z brachman $