rexd(1M)																  rexd(1M)

NAME

       rexd - RPC-based remote execution server

SYNOPSIS

       log_file] mountdir]

DESCRIPTION

       is  the	RPC server for remote command execution.  A is started by when a remote execution request is received (see inetd(1M)).	exits when
       command execution has completed.

       If the user ID (uid) in the remote execution request is assigned to a user on the server, executes the command as that user.  If no user on
       the  server  is	assigned  to  the  uid,  does  not execute the command.  The option and security file allow for better access control (see
       inetd.sec(4)).

       For noninteractive commands, standard output and error file descriptors are connected to sockets.  Interactive commands use  pseudo  termi-
       nals for standard input, output, and error (see pty(7)).

       If  the	file  system specified in the remote execution request is not already mounted on the server, uses NFS to mount the file system for
       the duration of the command execution (see nfs(7)).  mounts file systems with the and options.  For  more  details  on  mount  options  see
       mount(1M).   If the server cannot mount the file system, an error message is returned to the client.  By default, any mount points required
       by are created below To change the default location, use the option.

   Options
       recognizes the following options and command-line arguments:

	      Log any diagnostic, warning, and error messages to
			      log_file.  If log_file exists, appends messages to the file.  If log_file does not exist, creates it.  Messages  are
			      not logged if the option is not specified.

			      Information  logged  to the file includes date and time of the error, host name, process ID and name of the function
			      generating the error, and the error message.  Note that different RPC services can share a single log  file  because
			      enough information is included to uniquely identify each error.

	      Create temporary mount points below directory
			      mountdir.  By default, creates temporary mount points below The directory mountdir should have read and execute per-
			      mission for all users (mode 555).  Otherwise, denies execution for users that do not have read and  execute  permis-
			      sion.

	      Use increased security checking.
			      When started with the option, denies execution access to a client unless one of the following conditions is met:

			      o  The name of the client host is in file on the server.

			      o  The  user  on the server that is associated with the uid sent by the client has an entry in specifying the client
				 name on a line or the client name followed by at least one blank and the user's name.

				 For example, assume a user whose login name is is assigned to uid 7 on and executes the following command:

				 User on must have one of the following entries in

DIAGNOSTICS

       The following is a subset of the messages that could appear in the log file if the option  is  used.   Some  of	these  messages  are  also
       returned to the client.

	      was unable to
			  the user's current working file system.  See for more details.

	      The path name
			  mountdir, under which temporary mount points are created, is not a directory or does not exist.

	      could not find
			  command.

	      was denied permission to execute
			  command.

	      The executable file is currently open for writing.

	      was unable to execute
			  command.

	      does not allow execution as user

	      The uid	  uid is not assigned to a user on the server.

	      was started with the
			  option and the remote execution request did not meet either of the conditions required by the option.

	      The host	  host	on which the user's current working directory is located is not running Therefore, is unable to mount the required
			  file system (see mountd(1M)).

	      The host on which the client's current working directory is located
			  does not have the server on the export list for file system file_system containing the client's current  working  direc-
			  tory.  Therefore, is unable to mount the required file system.

WARNINGS

       The client's environment is simulated by but not completely recreated.  The simulation of the client's environment consists of mounting the
       file system containing the client's current working directory (if it is not already mounted) and setting the user's  environment  variables
       on  the	server to be the same as the user's environment variables on the client.  Therefore a command run by does not always have the same
       effect as a command run locally on the client.

       The protocol only identifies the client user by sending the uid of the client process and the host name of the client.	Therefore,  it	is
       very  difficult	for  to  perform  user	authentication.   If  a user on the server is assigned to the uid sent by the client, executes the
       requested command as that user.	If no user on the client is assigned to the uid sent by the client, returns an error.

       The option has been added to provide increased user authentication.  However, the authentication provided is not foolproof, and is  limited
       by the information passed by the protocol.

       In  order  to  simulate	the  client's  environment, mounts the file system containing the client's current working directory (if it is not
       already mounted).  This mount is intended to be temporary for the duration of the command.

       If mounts a file system, it attempts to the file system after the command has completed executing.  However, if receives a signal (see sig-
       nal(2)),  the  file  system  is not unmounted.  The file system remains mounted until the superuser executes the appropriate command or the
       server is rebooted.

       attempt to umount the file system can also fail if the file system is busy.  The file system is busy if it  contains  an  open  file  or  a
       user's  current	working  directory.  The file system remains mounted until the superuser executes the appropriate command or the server is
       rebooted.

       For more information on security issues, see Security issues and their consequences should be considered before configuring  to	run  on  a
       system.

FILES

       master pseudo terminals
       slave pseudo terminals
       master pseudo terminals
       slave pseudo terminals
       configuration file for		       inetd(1M)
       list of equivalent hosts
       user's private equivalence list
       temporary mount points for remote file systems where
					       xxxxx is a string of alpha numeric characters.

AUTHOR

       was developed by Sun Microsystems, Inc.

SEE ALSO

       on(1), inetd(1M), mount(1M), dfstab(4), inetd.conf(4), inetd.sec(4).

       Using and Administering NFS Services

																	  rexd(1M)