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man pages section 8: System Administration Commands

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Updated: Wednesday, July 27, 2022



in.rexecd, rexecd - remote execution server






in.rexecd is the server for the rexec(3C) routine. The server provides remote execution facilities with authentication based on user names and passwords. It is invoked automatically as needed by inetd(8), and then executes the following protocol:

  1. The server reads characters from the socket up to a null (\0) byte. The resultant string is interpreted as an ASCII number, base 10.

  2. If the number received in step 1 is non-zero, it is interpreted as the port number of a secondary stream to be used for the stderr. A second connection is then created to the specified port on the client's machine.

  3. A null terminated user name of at most 256 characters is retrieved on the initial socket.

  4. A null terminated password of at most 16 characters is retrieved on the initial socket.

  5. A null terminated command to be passed to a shell is retrieved on the initial socket. The length of the command is limited by the upper bound on the size of the system's argument list.

  6. in.rexecd then validates the user via the pam(3PAM) authentication process, as described under SECURITY below. If the authentication was successful, in.rexecd changes to the user's home directory, and establishes the user and group privileges of the user. If any of these steps fail the connection is aborted and a diagnostic message is returned.

  7. A null byte is returned on the connection associated with the stderr and the command line is passed to the normal login shell of the user. The shell inherits the network connections established by in.rexecd.


in.rexecd is IPv6–enabled. For more information, see the ip6(4P) man page.

The protocol underlying these functions uses weak authentication and offers no protection against spoofing or snooping of traffic. The in.rexecd server is disabled by default on Oracle Solaris and most other modern operating systems, and may be removed in future versions of Oracle Solaris. Use of the sshd(8) server is strongly recommended instead.


in.rexecd uses pam(3PAM) for authentication, account management, and session management. The PAM configuration policy, configured in /etc/pam.conf or per-service files in /etc/pam.d/, specifies the modules to be used for in.rexeced via the service name rexec. If there are no entries for the rexec service, then the entries for the “other” service will be used.

If the rexec configuration results in any PAM conversation prompts other than for the UNIX password, the conversation will fail and in.rexeced will report an authentication error and abort the connection.


See attributes(7) for descriptions of the following attributes:

Interface Stability

See Also

svcs(1), rexec(3C), pam(3PAM), ip6(4P), smf(7), attributes(7), inetadm(8), inetd(8), sshd(8), svcadm(8)


All diagnostic messages are returned on the connection associated with the stderr, after which any network connections are closed. An error is indicated by a leading byte with a value of 1 (0 is returned in step 7 above upon successful completion of all the steps prior to the command execution).

username too long

The name is longer than 256 characters.

password too long

The password is longer than 16 characters.

command too long

The command line passed exceeds the size of the argument list (as configured into the system).

Login incorrect.

No password file entry for the user name existed.

No remote directory.

The chdir command to the home directory failed.

Try again.

A fork by the server failed.

/usr/bin/sh: ...

The user's login shell could not be started.


The in.rexecd service is managed by the service management facility, smf(7), under the service identifier:


Administrative actions on this service, such as enabling, disabling, or requesting restart, can be performed using svcadm(8). Responsibility for initiating and restarting this service is delegated to inetd(8). Use inetadm(8) to make configuration changes and to view configuration information for this service. The service's status can be queried using the svcs(1) command.

This technology may be removed in a future release of Oracle Solaris.


The in.rexecd service has been present since the initial release of Solaris.

Support for IPv6 was added in Solaris 8.

The in.rexecd service was enabled by default in releases up through Solaris 9, but has been disabled by default since the Solaris 10 3/05 release.