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 rexec(1)                                                           rexec(1)

 NAME    [Toc]    [Back]
      remsh, rexec - execute from a remote shell

 SYNOPSIS    [Toc]    [Back]
      remsh host [-l username] [-n] command
            host [-l username] [-n] command

      rexec host [-l username] [-n] command

    In Kerberos V5 Network Authentication Environments:
      remsh host [-l username] [-f|-F] [-k realm] [-P] [-n] command
            host [-l username] [-f|-F] [-k realm] [-P] [-n] command

 DESCRIPTION    [Toc]    [Back]
      remsh connects to a specified host and executes a specified command.
      The host name can be either the official name or an alias as
      understood by gethostbyname() (see gethostent(3N) and hosts(4)).
      remsh copies its standard input (stdin) to the remote command, the
      standard output of the remote command to its standard output (stdout),
      and the standard error of the remote command to its standard error
      (stderr).  Hangup, interrupt, quit, terminate, and broken pipe signals
      are propagated to the remote command.  remsh exits when the sockets
      associated with stdout and stderr of the remote command are closed.
      This means that remsh normally terminates when the remote command does
      (see remshd(1M)).

      By default, remsh uses the following path when executing the specified


      remsh uses the default remote login shell with the -c option to
      execute the remote command.  If the default remote shell is csh, csh
      sources the remote .cshrc file before the command.  remsh cannot be
      used to run commands that require a terminal interface (such as vi) or
      commands that read their standard error (such as more).  In such
      cases, use rlogin or telnet instead (see rlogin(1) and telnet(1)).

      The remote account name used is the same as your local account name,
      unless you specify a different remote name with the -l option.  This
      remote account name must be equivalent to the originating account.  In
      addition, the remote host account name must also conform to other
      rules, which differ depending upon whether the remote host is
      operating in a Kerberos V5 Network Authentication, i.e., secure
      environment, or not.

      In a non-secure, or traditional environment, the remote account name
      must be equivalent to the originating account; no provision is made
      for specifying a password with a command.  For more details about
      equivalent hosts and how to specify them, see hosts.equiv(4).  The
      files inspected by remshd on the remote host are /etc/hosts.equiv and

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 rexec(1)                                                           rexec(1)

      $HOME/.rhosts (see remshd(1M)).

      In a Kerberos V5 Network Authentication environment, the local host
      must be successfully authenticated before the remote account name is
      checked for proper authorization.  The authorization mechanism is
      dependent on the command line options used to invoke remshd on the
      remote host (i.e., -K, -R, -r, or -k).  For more information on
      Kerberos authentication and authorization see the Secure Internet
      Services man page, sis(5) and remshd(1M).

      Although Kerberos authentication and authorization may apply, the
      Kerberos mechanism is not applied to the command or to its response.
      All the information that is transferred between the local and remote
      host is still sent in cleartext over the network.

      In a secure or Kerberos V5-based environment, the following command
      line options are available:

           -f          Forward the ticket granting ticket (TGT) to the
                       remote system.  The TGT is not forwardable from that
                       remote system.

           -F          Forward the TGT to the remote system and have it
                       forwardable from there to another remote system.  The
                       -f option and -F option are mutually exclusive.

           -k realm    Obtain tickets from the remote host in the specified
                       realm instead of the remote host's default realm as
                       specified in the configuration file krb.realms.

           -P          Disable Kerberos authentication.

      Note: The Kerberos authentication and authorization mechanism and the
      above Kerberos specific options are not supported in IPv6 enabled

      If command, is not specified, instead of executing a single command,
      you will be logged in on the remote host using rlogin (see rlogin(1)).
      Any rlogin options typed in on the command line are transmitted to
      rlogin.  If no command and the option -P are specified, rlogin will be
      invoked with -P to indicate that Kerberos authentication (or secure
      access) is not necessary. This means that if a password is requested,
      the password will be sent in cleartext.  If command is specified,
      options specific to rlogin are ignored by remsh.

      By default, remsh reads its standard input and sends it to the remote
      command because remsh has no way to determine whether the remote
      command requires input.  The -n option redirects standard input to
      remsh from /dev/null.  This is useful when running a shell script
      containing a remsh command, since otherwise remsh may use input not
      intended for it.  The -n option is also useful when running remsh in

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 rexec(1)                                                           rexec(1)

      the background from a job control shell, /usr/bin/csh or /usr/bin/ksh.
      Otherwise, remsh stops and waits for input from the terminal keyboard
      for the remote command.  /usr/bin/sh automatically redirects its input
      from /dev/null when jobs are run in the background.

      Host names for remote hosts can also be commands (linked to remsh) in
      the directory /usr/hosts.  If this directory is specified in the $PATH
      environment variable, you can omit remsh.  For example, if remotehost
      is the name of a remote host, /usr/hosts/remotehost is linked to
      remsh, and if /usr/hosts is in your search path, the command

           remotehost command

      executes command on remotehost, and the command


      is equivalent to

           rlogin remotehost

      The rexec command works in the same way as remsh except that it uses
      the rexec() library routine and rexecd for command execution (see
      rexec(3N) and rexecd(1M)) and does not support Kerberos
      authentication.  rexec prompts for a password before executing the
      command instead of using hosts.equiv for authentication.  It should be
      used in instances where a password to a remote account is known but
      there are insufficient permissions for remsh.

 EXAMPLES    [Toc]    [Back]
      Shell metacharacters that are not quoted are interpreted on the local
      host; quoted metacharacters are interpreted on the remote host.  Thus
      the command line:

           remsh otherhost cat remotefile >> localfile

      appends the remote file remotefile to the local file localfile, while
      the command line

           remsh otherhost cat remotefile ">>" otherremotefile

      appends remotefile to the remote file otherremotefile.

      If the remote shell is /usr/bin/sh, the following command line sets up
      the environment for the remote command before executing the remote

           remsh otherhost . .profile 2>&- \; command

      The 2>&- throws away error messages generated by executing .profile
      when stdin and stdout are not a terminal.

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 rexec(1)                                                           rexec(1)

      The following command line runs remsh in the background on the local
      system, and the output of the remote command comes to your terminal

           remsh otherhost -n command &

      The background remsh completes when the remote command does.

      The following command line causes remsh to return immediately without
      waiting for the remote command to complete:

           remsh otherhost -n "command 1>&- 2>&- &"

      (See remshd(1M) and sh(1)).  If your login shell on the remote system
      is csh, use the following form instead:

           remsh otherhost -n "sh -c \"command 1>&- 2>&- &\""

 RETURN VALUE    [Toc]    [Back]
      If remsh fails to set up the secondary socket connection, it returns
      2.  If it fails in some other way, it returns 1.  If it fully succeeds
      in setting up a connection with remshd, it returns 0 once the remote
      command has completed.  Note that the return value of remsh bears no
      relation to the return value of the remote command.

 DIAGNOSTICS    [Toc]    [Back]
      Besides the errors listed below, errors can also be generated by the
      library functions rcmd() and rresvport().  In the case of IPv6
      systems, the library functions rcmd() and rresvport() are replaced by
      rcmd_af() and rresvport_af(); respectively, and can generate errors
      (see rcmd(3N) and rcmd_af(3N)).  These errors are preceded by the name
      of the library function that generated them.  remsh can produce the
      following diagnostic messages:

           Error! could not retrieve authentication type.
           Please notify sys admin.
                There are two authentication mechanisms used by remsh.  One
                authentication mechanism is based on Kerberos and the other
                is not.  The type of authentication mechanism is obtained
                from a system file which is updated by inetsvcs_sec (see
                inetsvcs_sec(1M)).  If the system file does not contain
                known authentication types, the above error is displayed.

           rlogin: ...
                Error in executing rlogin (rlogin is executed when the user
                does not specify any commands to be executed).  This is
                followed by the error message specifying why the execution

           shell/tcp: Unknown service
                The ``shell'' service specification is not present in the

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 rexec(1)                                                           rexec(1)

                /etc/services file.

           Can't establish stderr
                remsh cannot establish secondary socket connection for

           <system call>: ...
                Error in executing system call.  Appended to this error is a
                message specifying the cause of the failure.

           There is no entry for you (user ID uid) in /etc/passwd
                Check with the system administrator to see if your entry in
                the password file has been deleted by mistake.

      Kerberos-specific errors are listed in sis(5).

 WARNINGS    [Toc]    [Back]
      For security reasons, the /etc/hosts.equiv and .rhosts files should
      exist, even if empty, and they should be readable and writable only by
      the owner.  Note also that all information, including any passwords
      asked for, is passed unencrypted between the two hosts.

      If remsh is run with an interactive command, it hangs.

 DEPENDENCIES    [Toc]    [Back]
      remsh is the same service as rsh on BSD systems.  The name was changed
      due to a conflict with the existing System V command rsh (restricted

 AUTHOR    [Toc]    [Back]
      remsh was developed by the University of California, Berkeley.

 FILES    [Toc]    [Back]
      /usr/hosts/*       for version of the command invoked only with

 SEE ALSO    [Toc]    [Back]
      rlogin(1), remshd(1M), rexecd(1M), inetsvcs_sec(1M), gethostent(3N),
      rcmd(3N), rcmd_af(3N), rexec(3N), hosts.equiv(4), hosts(4).

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[ Back ]
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