NAME
debconf.conf - debconf configuration file
DESCRIPTION
Debconf is a configuration system for Debian packages.
/etc/debconf.conf and ~/.debconfrc are configuration files debconf uses
to determine which databases it should use. These databases are used
for storing two types of information; dynamic config data the user
enters into it, and static template data. Debconf offers a flexible,
extensible database backend. New drivers can be created with a minimum
of effort, and sets of drivers can be combined in various ways.
SYNOPSIS
# This is a sample config file that is
# sufficient to use debconf.
Config: configdb
Templates: templatedb
Name: configdb
Driver: File
Filename: /var/cache/debconf/config.dat
Name: templatedb
Driver: File
Mode: 644
Filename: /var/cache/debconf/templates.dat
FILE FORMAT
The format of this file is a series of stanzas, each separated by at
least one wholly blank line. Comment lines beginning with a "#"
character are ignored.
The first stanza of the file is special, is used to configure debconf
as a whole. Two fields are required to be in this first stanza:
Config Specifies the name of the database from which to load
config data.
Templates
Specifies the name of the database to use for the
template cache.
Additional fields that can be used include:
Frontend
The frontend Debconf should use, overriding any frontend
set in the debconf database.
Priority
The priority Debconf should use, overriding any priority
set in the debconf database.
Admin-Email
The email address Debconf should send mail to if it needs
to make sure that the admin has seen an important
message. Defaults to "root", but can be set to any valid
email address to send the mail there. If you prefer to
never have debconf send you mail, specify a blank
address. This can be overridden on the fly with the
DEBCONF_ADMIN_EMAIL environment variable.
Debug If set, this will cause debconf to output debugging
information to standard error. The value it is set to can
be something like "user", "developer", "db", or a regular
expression. Typically, rather than setting it permanently
in a config file, you will only want to temporarily turn
on debugging, and the DEBCONF_DEBUG environment variable
can be set instead to accomplish that.
NoWarnings
If set, this will make debconf not display warnings about
various things. This can be overridden on the fly with
the DEBCONF_NOWARNINGS environment variable.
Log Makes debconf log debugging information as it runs, to
the syslog. The value it is set to controls that is
logged. See Debug, above for an explanation of the values
that can be set to control what is logged.
Terse If set to "true", makes some debconf frontends use a
special terse display mode that outputs as little as
possible. Defaults to false. Terse mode may be
temporarily set via the DEBCONF_TERSE environment
variable.
For example, the first stanza of a file might look like this:
Config: configdb
Templates: templatedb
Each remaining stanza in the file sets up a database. A database stanza
begins by naming the database:
Name: configdb
Then it indicates what database driver should be used for this
database. See DRIVERS, below, for information about what drivers are
available.
Driver: File
You can indicate that the database is not essential to the proper
functioning of debconf by saying it is not required. This will make
debconf muddle on if the database fails for some reason.
Required: false
You can mark any database as readonly and debconf will not write
anything to it.
Readonly: true
You can also limit what types of data can go into the database with
Accept- and Reject- lines; see ACCESS CONTROLS, below.
The remainder of each database stanza is used to provide configuration
specific to that driver. For example, the Text driver needs to know a
directory to put the database in, so you might say:
Filename: /var/cache/debconf/config.dat
DRIVERS
A number of drivers are available, and more can be written with little
difficulty. Drivers come in two general types. First there are real
drivers -- drivers that actually access and store data in some kind of
database, which might be on the local filesystem, or on a remote
system. Then there are meta-drivers that combine other drivers together
to form more interesting systems. Let’s start with the former.
File
This database driver allows debconf to store a whole
database in a single flat text file. This makes it easy
to archive, transfer between machines, and edit. It is
one of the more compact database formats in terms of disk
space used. It is also one of the slowest.
On the downside, the entire file has to be read in each
time debconf starts up, and saving it is also slow.
The following things are configurable for this driver.
Filename
The file to use as the database. This is a
required field.
Mode The permissions to create the file with if
it does not exist. Defaults to 600, since
the file could contain passwords in some
circumstances.
Format The format of the file. See FORMATS below.
Defaults to using a rfc-822 like format.
Backup Whether a backup should be made of the old
file before changing it. Defaults to
true.
As example stanza setting up a database using this
driver:
Name: mydb
Driver: File
Filename: /var/cache/debconf/mydb.dat
DirTree
This database driver allows debconf to store data in a
hierarchical directory structure. The names of the
various debconf templates and questions are used as-is to
form directories with files in them. This format for the
database is the easiest to browse and fiddle with by
hand. It has very good load and save speeds. It also
typically occupies the most space, since a lot of small
files and subdirectories do take up some additional room.
The following things are configurable for this driver.
Directory
The directory to put the files in.
Required.
Extension
An extension to add to the names of files.
Must be set to a non-empty string;
defaults to ".dat"
Format The format of the file. See FORMATS below.
Defaults to using a rfc-822 like format.
Backup Whether a backup should be made of the old
file before changing it. Defaults to
true.
As example stanza setting up a database using this
driver:
Name: mydb
Driver: DirTree
Directory: /var/cache/debconf/mydb
Extension: .txt
PackageDir
This database driver is a compromise between the File and
DirTree databases. It uses a directory, in which there is
(approximately) one file per package that uses debconf.
This is fairly fast, while using little more room than
the File database driver.
This driver is configurable in the same ways as is the
DirTree driver, plus:
Mode The permissions to create files with. Defaults to
600, since the files could contain passwords in
some circumstances.
As example stanza setting up a database using this
driver:
Name: mydb
Driver: PackageDir
Directory: /var/cache/debconf/mydb
LDAP
WARNING: This database driver is currently experimental.
Use with caution.
This database driver accesses a LDAP directory for
debconf configuration data.Due to the nature of the
beast, LDAP directories should typically be accessed in
read-only mode. This is because multiple accesses can
take place, and it’s generally better for data
consistency if nobody tries to modify the data while this
is happening. Of course, write access is supported for
those cases where you do want to update the config data
in the directory.
For information about setting up a LDAP server for
debconf, read /usr/share/doc/debconf-doc/README.LDAP
(from the debconf-doc package).
To use this database driver, you must have the libnet-
ldap-perl package installed. Debconf suggests that
package, but does not depend on it.
Please carefully consider the security implications of
using a remote debconf database. Unless you trust the
source, and you trust the intervening network, it is not
a very safe thing to do.
The following things are configurable for this driver.
server The host name or IP address of an LDAP
server to connect to.
port The port on which to connect to the LDAP
server. If none is given, the default
port is used.
basedn The DN under which all config items will
be stored. Each config item will be
assumed to live in a DN of cn=<item
name>,<Base DN>. If this structure is not
followed, all bets are off.
binddn The DN to bind to the directory as.
Anonymous bind will be used if none is
specified.
bindpasswd
The password to use in an authenticated
bind (used with binddn, above). If not
specified, anonymous bind will be used.
This option should not be used in the
general case. Anonymous binding should be
sufficient most of the time for read-only
access. Specifying a bind DN and password
should be reserved for the occasional case
where you wish to update the debconf
configuration data.
keybykey
Enable access to individual LDAP entries,
instead of fetching them all at once in
the beginning. This is very useful if you
want to monitor your LDAP logs for
specific debconf keys requested. In this
way, you could also write custom handling
code on the LDAP server part.
Note that when this option is enabled, the
connection to the LDAP server is kept
active during the whole Debconf run. This
is a little different from the all-in-one
behavior where two brief connections are
made to LDAP; in the beginning to retrieve
all the entries, and in the end to save
eventual changes.
An example stanza setting up a database using this
driver, assuming the remote database is on example.com
and can be accessed anonymously:
Name: ldapdb
Driver: LDAP
Readonly: true
Server: example.com
BaseDN: cn=debconf,dc=example,dc=com
KeyByKey: 0
Another example, this time the LDAP database is on
localhost, and can be written to:
Name: ldapdb
Driver: LDAP
Server: localhost
BaseDN: cn=debconf,dc=domain,dc=com
BindPasswd: secret
KeyByKey: 1
Pipe
This special-purpose database driver reads and writes the
database from standard input/output. It may be useful for
people with special needs.
The following things are configurable for this driver.
Format The format to read and write. See FORMATS
below. Defaults to using a rfc-822 like
format.
Infd File descriptor number to read from.
Defaults to reading from stdin. If set to
"none", the database will not read any
data on startup.
Outfd File descriptor number to write to.
Defaults to writing to stdout. If set to
"none", the database will be thrown away
on shutdown.
That’s all of the real drivers, now moving on to meta-drivers..
Stack
This driver stacks up a number of other databases (of any
type), and allows them to be accessed as one. When
debconf asks for a value, the first database on the stack
that contains the value returns it. If debconf writes
something to the database, the write normally goes to the
first driver on the stack that has the item debconf is
modifying, and if none do, the new item is added to the
first writable database on the stack.
Things become more interesting if one of the databases on
the stack is readonly. Consider a stack of the databases
foo, bar, and baz, where foo and baz are both readonly.
Debconf wants to change an item, and this item is only
present in baz, which is readonly. The stack driver is
smart enough to realize that won’t work, and it will copy
the item from baz to bar, and the write will take place
in bar. Now the item in baz is shadowed by the item in
bar, and it will not longer be visible to debconf.
This kind of thing is particularly useful if you want to
point many systems at a central, readonly database, while
still allowing things to be overridden on each system.
When access controls are added to the picture, stacks
allow you to do many other interesting things, like
redirect all passwords to one database while a database
underneath it handles everything else.
Only one piece of configuration is needed to set up a
stack:
Stack This is where you specify a list of other
databases, by name, to tell it what makes
up the stack.
For example:
Name: megadb
Driver: stack
Stack: passworddb, configdb, companydb
WARNING: The stack driver is not very well tested yet.
Use at your own risk.
Backup
This driver passes all requests on to another database
driver. But it also copies all write requests to a backup
database driver.
You must specify the following fields to set up this
driver:
Db The database to read from and write to.
Backupdb
The name of the database to send copies of
writes to.
For example:
Name: backup
Driver: Backup
Db: mydb
Backupdb: mybackupdb
Debug
This driver passes all requests on to another database
driver, outputting verbose debugging output about the
request and the result.
You must specify the following fields to set up this
driver:
Db The database to read from and write to.
ACCESS CONTROLS
When you set up a database, you can also use some fields to
specify access controls. You can specify that a database only
accepts passwords, for example, or make a database only accept
things with "foo" in their name.
Readonly
As was mentioned earlier, this access control, if set to
"true", makes a database readonly. Debconf will read
values from it, but will never write anything to it.
Accept-Name
The text in this field is a perl-compatible regular
expression that is matched against the names of items as
they are requested from the database. Only if an items
name matches the regular expression, will the database
allow debconf to access or modify it.
Reject-Name
Like Accept-Name, except any item name matching this
regular expression will be rejected.
Accept-Type
Another regular expression, this matches against the type
of the item that is being accessed. Only if the type
matches the regex will access be granted.
Reject-Type
Like Accept-Type, except any type matching this regular
expression will be rejected.
FORMATS
Some of the database drivers use format modules to control the
actual format in which the database is stored on disk. These
formats are currently supported:
822 This is a file format loosely based upon the rfc-822
format for email message headers. Similar formats are
used throughout Debian; in the dpkg status file, and so
on.
EXAMPLE
Here is a more complicated example of a debconf.conf file.
# This stanza is used for general debconf setup.
Config: stack
Templates: templates
Log: developer
Debug: developer
# This is my own local database.
Name: mydb
Driver: DirTree
Directory: /var/cache/debconf/config
# This is another database that I use to hold
# only X server configuration.
Name: X
Driver: File
Filename: /etc/X11/debconf.dat
Mode: 644
# It’s sorta hard to work out what questions
# belong to X; it should be using a deeper
# tree structure so I could just match on ^X/
# Oh well.
Accept-Name: xserver|xfree86|xbase
# This is our company’s global, read-only
# (for me!) debconf database.
Name: company
Driver: LDAP
Server: debconf.foo.com
BaseDN: cn=debconf,dc=foo,dc=com
BindDN: uid=admin,dc=foo,dc=com
BindPasswd: secret
Readonly: true
# I don’t want any passwords that might be
# floating around in there.
Reject-Type: password
# If this db is not accessible for whatever
# reason, carry on anyway.
Required: false
# I use this database to hold
# passwords safe and secure.
Name: passwords
Driver: File
Filename: /etc/debconf/passwords
Mode: 600
Accept-Type: password
# Let’s put them all together
# in a database stack.
Name: stack
Driver: Stack
Stack: passwords, X, mydb, company
# So, all passwords go to the password database.
# Most X configuration stuff goes to the X
# database, and anything else goes to my main
# database. Values are looked up in each of those
# in turn, and if none has a particular value, it
# is looked up in the company-wide LDAP database
# (unless it’s a password).
# A database is also used to hold templates. We
# don’t need to make this as fancy.
Name: templates
Driver: File
Mode: 644
Format: 822
Filename: /var/cache/debconf/templates
NOTES
If you use something like ${HOME} in this file, it will be
replaced with the value of the named environment variable.
Environment variables can also be used to override the databases
on the fly, see debconf(7)
The field names (the part of the line before the colon) is case-
insensitive. The values, though, are case sensitive.
PLANNED ENHANCEMENTS
More drivers and formats. Some ideas include: A SQL driver, with
the capability to access a remote database. A DHCP driver, that
makes available some special things like hostname, IP address,
and DNS servers. A driver that pulls values out of public DNS
records TXT fields. A format that is compatible with the output
of cdebconf. An override driver, which can override the value
field or flags of all requests that pass through it.
FILES
/etc/debconf.conf
~/.debconfrc
SEE ALSO
debconf(7)
AUTHOR
Joey Hess <joeyh@debian.org>