rexd(1M)rexd(1M)NAMErexd - 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 com‐
mand 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 terminals
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 sys‐
tems with the and options. For more details on mount options see
mount(1M). If the server cannot mount the file system, an error mes‐
sage 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, cre‐
ates 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 ser‐
vices 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 permission for all users (mode
555). Otherwise, denies execution for users
that do not have read and execute permission.
Use increased security checking.
When started with the option, denies execution
access to a client unless one of the following
conditions is met:
· The name of the client host is in file on the
server.
· 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 directory. 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 com‐
mand 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 com‐
mand 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 sys‐
tem.
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 ALSOon(1), inetd(1M), mount(1M), dfstab(4), inetd.conf(4), inetd.sec(4).
Using and Administering NFS Services
rexd(1M)
