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xauth - X authority file utility
xauth [ -f authfile ] [ -vqibn ] [ command arg ... ]
The xauth program is used to edit and display the authorization infor-
mation used in connecting to the X server. This program is usually
used to extract authorization records from one machine and merge them
in on another (as is the case when using remote logins or granting
access to other users). Commands (described below) may be entered
interactively, on the xauth command line, or in scripts. Note that
this program does not contact the X server except when the generate
command is used. Normally xauth is not used to create the authority
file entry in the first place; xdm does that.
The following options may be used with xauth. They may be given indi-
vidually (e.g., -q -i) or may combined (e.g., -qi).
This option specifies the name of the authority file to use.
By default, xauth will use the file specified by the XAUTHORITY
environment variable or .Xauthority in the user's home direc-
-q This option indicates that xauth should operate quietly and not
print unsolicited status messages. This is the default if an
xauth command is given on the command line or if the standard
output is not directed to a terminal.
-v This option indicates that xauth should operate verbosely and
print status messages indicating the results of various opera-
tions (e.g., how many records have been read in or written
out). This is the default if xauth is reading commands from
its standard input and its standard output is directed to a
-i This option indicates that xauth should ignore any authority
file locks. Normally, xauth will refuse to read or edit any
authority files that have been locked by other programs (usu-
ally xdm or another xauth).
-b This option indicates that xauth should attempt to break any
authority file locks before proceeding. Use this option only
to clean up stale locks.
-n This option indicates that xauth should not attempt to resolve
any hostnames, but should simply always print the host address
as stored in the authority file.
The following commands may be used to manipulate authority files:
add displayname protocolname hexkey
An authorization entry for the indicated display using the
given protocol and key data is added to the authorization file.
The data is specified as an even-lengthed string of hexadecimal
digits, each pair representing one octet. The first digit of
each pair gives the most significant 4 bits of the octet, and
the second digit of the pair gives the least significant 4
bits. For example, a 32 character hexkey would represent a
128-bit value. A protocol name consisting of just a single
period is treated as an abbreviation for MIT-MAGIC-COOKIE-1.
generate displayname protocolname [trusted|untrusted]
[timeout seconds] [group group-id] [data hexdata]
This command is similar to add. The main difference is that
instead of requiring the user to supply the key data, it con-
nects to the server specified in displayname and uses the SECU-
RITY extension in order to get the key data to store in the
authorization file. If the server cannot be contacted or if it
does not support the SECURITY extension, the command fails.
Otherwise, an authorization entry for the indicated display
using the given protocol is added to the authorization file. A
protocol name consisting of just a single period is treated as
an abbreviation for MIT-MAGIC-COOKIE-1.
If the trusted option is used, clients that connect using this
authorization will have full run of the display, as usual. If
untrusted is used, clients that connect using this authoriza-
tion will be considered untrusted and prevented from stealing
or tampering with data belonging to trusted clients. See the
SECURITY extension specification for full details on the
restrictions imposed on untrusted clients. The default is
The timeout option specifies how long in seconds this autho-
rization will be valid. If the authorization remains unused
(no clients are connected with it) for longer than this time
period, the server purges the authorization, and future
attempts to connect using it will fail. Note that the purging
done by the server does not delete the authorization entry from
the authorization file. The default timeout is 60 seconds.
The group option specifies the application group that clients
connecting with this authorization should belong to. See the
application group extension specification for more details.
The default is to not belong to an application group.
The data option specifies data that the server should use to
generate the authorization. Note that this is not the same
data that gets written to the authorization file. The inter-
pretation of this data depends on the authorization protocol.
The hexdata is in the same format as the hexkey described in
the add command. The default is to send no data.
[n]extract filename displayname...
Authorization entries for each of the specified displays are
written to the indicated file. If the nextract command is
used, the entries are written in a numeric format suitable for
non-binary transmission (such as secure electronic mail). The
extracted entries can be read back in using the merge and
nmerge commands. If the filename consists of just a single
dash, the entries will be written to the standard output.
Authorization entries for each of the specified displays (or
all if no displays are named) are printed on the standard out-
put. If the nlist command is used, entries will be shown in
the numeric format used by the nextract command; otherwise,
they are shown in a textual format. Key data is always dis-
played in the hexadecimal format given in the description of
the add command.
Authorization entries are read from the specified files and are
merged into the authorization database, superceding any match-
ing existing entries. If the nmerge command is used, the
numeric format given in the description of the extract command
is used. If a filename consists of just a single dash, the
standard input will be read if it hasn't been read before.
Authorization entries matching the specified displays are
removed from the authority file.
The specified file is treated as a script containing xauth com-
mands to execute. Blank lines and lines beginning with a sharp
sign (#) are ignored. A single dash may be used to indicate
the standard input, if it hasn't already been read.
info Information describing the authorization file, whether or not
any changes have been made, and from where xauth commands are
being read is printed on the standard output.
exit If any modifications have been made, the authority file is
written out (if allowed), and the program exits. An end of
file is treated as an implicit exit command.
quit The program exits, ignoring any modifications. This may also
be accomplished by pressing the interrupt character.
A description of all commands that begin with the given string
(or all commands if no string is given) is printed on the stan-
? A short list of the valid commands is printed on the standard
Display names for the add, [n]extract, [n]list, [n]merge, and remove
commands use the same format as the DISPLAY environment variable and
the common -display command line argument. Display-specific informa-
tion (such as the screen number) is unnecessary and will be ignored.
Same-machine connections (such as local-host sockets, shared memory,
and the Internet Protocol hostname localhost) are referred to as host-
name/unix:displaynumber so that local entries for different machines
may be stored in one authority file.
The most common use for xauth is to extract the entry for the current
display, copy it to another machine, and merge it into the user's
authority file on the remote machine:
% xauth extract - $DISPLAY | rsh otherhost xauth merge -
The following command contacts the server :0 to create an authorization
using the MIT-MAGIC-COOKIE-1 protocol. Clients that connect with this
authorization will be untrusted.
% xauth generate :0 .
This xauth program uses the following environment variables:
to get the name of the authority file to use if the -f option
HOME to get the user's home directory if XAUTHORITY isn't defined.
default authority file if XAUTHORITY isn't defined.
Users that have unsecure networks should take care to use encrypted
file transfer mechanisms to copy authorization entries between
machines. Similarly, the MIT-MAGIC-COOKIE-1 protocol is not very use-
ful in unsecure environments. Sites that are interested in additional
security may need to use encrypted authorization mechanisms such as
Spaces are currently not allowed in the protocol name. Quoting could
be added for the truly perverse.
Jim Fulton, MIT X Consortium
4.5.0 XFree86 XAUTH(1)