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xfs

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
INPUT FILES
CATALOGUE DIR
OUTPUT FILES
ASYNCHRONOUS EVENTS
BUGS
FUTURE DIRECTIONS
AUTHORS
SEE ALSO

NAME

xfs − X font server

SYNOPSIS

xfs [ −config configuration_file ] [ −daemon ] [ −droppriv ] [ −inetd ] [ −ls listen_socket ] [ −nodaemon ] [ −port tcp_port ] [ −user username ]

DESCRIPTION

xfs is the X Window System font server. It supplies fonts to X Window System display servers. The server is usually run by a system administrator, and started via init(8) or inetd(8). Users may also wish to start private font servers for specific sets of fonts.

To connect to a font server, see the documentation for your X server; it likely supports the syntax documented in the “FONT SERVER NAMES” section of X(7).

OPTIONS

−config configuration_file

specifies the configuration file xfs will use. If this parameter is not specified, xfs will read its configuration from the default file, /etc/X11/fs/config.

−daemon

instructs xfs to fork and go into the background automatically at startup. If this option is not specified, xfs will run as a regular process (unless it was built to daemonize by default). When running as a daemon, xfs will attempt to create a file in which it stores its process ID, and will delete that file upon exit;

−droppriv

instructs xfs to attempt to run as user and group xfs (unless the −user option is used). This has been implemented for security reasons, as xfs may have undiscovered buffer overflows or other paths for possible exploit, both local and remote. When using this option, you may also wish to specify ‘no−listen = tcp’ in the config file, which ensures that xfs will not to use a TCP port at all. By default, xfs runs with the user and group IDs of the user who invoked it.

−inetd

informs xfs that it is being started by inetd, and that a listening socket on the appropriate port is being passed as standard input. Assumes that inetd is configured to "wait" mode, and will thus allow xfs to handle listening for and accepting further connections on this port. This allows xfs to be started on demand when the first font client connects. When using this option, the -daemon and -port flags are ignored.

−ls listen_socket

specifies a file descriptor which is already set up to be used as the listen socket. This option is only intended to be used by the font server itself when automatically spawning another copy of itself to handle additional connections.

−nodaemon

instructs xfs not to daemonize (fork and detach from its controlling terminal). This option only has an effect if xfs is built to daemonize by default, which is not the stock configuration.

−port tcp_port

specifies the TCP port number on which the server will listen for connections. The default port number is 7100. This option is ignored if xfs is configured to not listen to TCP transports at all (see “Configuration File Format” below).

−user username

instructs xfs to run as the user username. See −droppriv for why this may be desired. By default, xfs runs with the user and group IDs of the user who invoked it.

INPUT FILES

xfs reads and serves any font file format recognized by the X server itself. It locates font files through the specification of a catalogue, which is declared in xfs’s configuration file.

Configuration File Format
xfs reads its configuration from a text file (see the −config option in the “OPTIONS” section above). The configuration language is a list of keyword and value pairs. Each keyword is followed by an equals sign (‘=’) and then the desired value.

Recognized keywords include:
alternate−servers (list of strings)

lists alternate servers for this font server. See the “FONT SERVER NAMES” section of X(7) for the syntax of the string.

catalogue (list of strings)

declares as ordered list of font path element names from which fonts will be served. The current implementation only supports a single catalogue ("all") containing all of the specified fonts. A special directory with symlinks to font paths can be specified using a catalogue:<dir> entry. See the CATALOGUE DIR section below for details.

client−limit (cardinal)

determines the number of clients this font server will support before refusing service. This is useful for tuning the load on each individual font server.

clone−self (boolean)

indicates whether this font server should attempt to clone itself when the number of connected clients reaches the client−limit.

default−point−size (cardinal)

The default pointsize (in decipoints) for font requests that don’t specify a point size. The default is 120.

default−resolutions (list of resolutions)

indicates the resolutions the server supports by default. This information may be used as a hint for pre-rendering, and substituted into requests for scaled fonts which do not specify a resolution. A resolution is a comma-separated pair of horizontal and vertical resolutions in pixels per inch. Multiple resolutions are separated by commas.

deferglyphs (string)

sets the mode for delayed fetching and caching of glyphs. string should be one of ‘none’, meaning glyphs deferment is disabled, ‘all’, meaning it is enabled for all fonts, and ‘16’, meaning it is enabled only for 16-bit fonts.

error−file (string)

indicates the filename of the error file. All warnings and errors will be logged here, unless use−syslog is set to a true value (see below).

no−listen (trans-type)

disables the specified transport type. For example, TCP/IP connections can be disabled with ‘no−listen = tcp’.

port (cardinal)

indicates the TCP port on which the server will listen for connections.

use−syslog (boolean)

determines whether errors and diagnostics should be reported via syslog(3) (on supported systems) instead of being written to the error−file (see above).

CATALOGUE DIR

You can specify a special kind of font path in the form catalogue:<dir>. The directory specified after the catalogue: prefix will be scanned for symlinks and each symlink destination will be added as a local fontfile FPE.

The symlink can be suffixed by attributes such as ’unscaled’, which will be passed through to the underlying fontfile FPE. The only exception is the newly introduced ’pri’ attribute, which will be used for ordering the font paths specified by the symlinks.

An example configuration:

75dpi:unscaled:pri=20 −> /usr/share/X11/fonts/75dpi
ghostscript:pri=60 −> /usr/share/fonts/default/ghostscript
misc:unscaled:pri=10 −> /usr/share/X11/fonts/misc
type1:pri=40 −> /usr/share/X11/fonts/Type1
type1:pri=50 −> /usr/share/fonts/default/Type1

This will add /usr/share/X11/fonts/misc as the first FPE with the attribute the attribute unscaled etc. This is functionally equivalent to setting the following font path:

/usr/share/X11/fonts/misc:unscaled,
/usr/share/X11/fonts/75dpi:unscaled,
/usr/share/X11/fonts/Type1,
/usr/share/fonts/default/Type1,
/usr/share/fonts/default/ghostscript

Example Configuration File
#
# sample font server configuration file
#

# allow a max of 10 clients to connect to this font server.
client−limit = 10

# When a font server reaches the above limit, start up a new one.
clone−self = on

# Identify alternate font servers for clients to use.
alternate−servers = hansen:7101,hansen:7102

# Look for fonts in the following directories. The first is a set of
# TrueType outlines, the second is a set of misc bitmaps (such as terminal
# and cursor fonts), and the last is a set of 100dpi bitmaps.
#
catalogue = /usr/share/X11/fonts/TTF,
/usr/share/X11/fonts/misc,
/usr/share/X11/fonts/100dpi/

# in 12 points, decipoints
default−point−size = 120

# 100 x 100 and 75 x 75
default−resolutions = 100,100,75,75

# Specify our log filename.
error−file = /var/log/xfs.log

# Direct diagnostics to our own log file instead of using syslog.
use−syslog = off

OUTPUT FILES

When operating in daemon mode, xfs sends diagnostic messages (errors and warnings) to the log file specified by the error-file configuration variable by default. However, these messages can be sent to an alternate location via the error−file and use−syslog configuration variables; see “Configuration File Format”, above.

ASYNCHRONOUS EVENTS

xfs handles the following signals specially:
SIGTERM

causes the font server to exit cleanly.

SIGUSR1

causes xfs to re-read its configuration file.

SIGUSR2

causes xfs to flush any cached data it may have.

SIGHUP

causes xfs to reset, closing all active connections and re-reading the configuration file.

BUGS

Multiple catalogues should be supported.

FUTURE DIRECTIONS

Significant further development of xfs is unlikely. One of the original motivations behind it was the single-threaded nature of the X server — a user’s X session could seem to ‘freeze up’ while the X server took a moment to rasterize a font. This problem with the X server, which remains single-threaded in all popular implementations to this day, has been mitigated on two fronts: machines have gotten much faster, and client-side font rendering (particularly via the Xft library) is the norm in contemporary software.

AUTHORS

Dave Lemke, Network Computing Devices, Inc
Keith Packard, Massachusetts Institute of Technology

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