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man pages section 1M: System Administration Commands

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Updated: July 2017



in.rlogind, rlogind - remote login server


/usr/sbin/in.rlogind [-k5eExXciPp] [-s tos] [-S keytab] 
     [-M realm]


in.rlogind is the server for the rlogin(1) program. The server provides a remote login facility with authentication based on Kerberos V5 or privileged port numbers.

in.rlogind is invoked by inetd(1M) when a remote login connection is established. When Kerberos V5 authentication is required (see option – k below), the authentication sequence is as follows:

  • Check Kerberos V5 authentication.

  • Check authorization according to the rules in krb5_auth_rules(5).

  • Prompt for a password if any checks fail and the PAM configuration (see pam.conf(4)) is configured to do so.

In order for Kerberos authentication to work, a host/<FQDN> Kerberos principal must exist for each Fully Qualified Domain Name associated with the in.rlogind server. Each of these host/<FQDN> principals must have a keytab entry in the /etc/krb5/krb5.keytab file on the in.rlogind server. An example principal might be:


See kadmin(1M) for instructions on adding a principal to a krb5.keytab file. See Managing Kerberos and Other Authentication Services in Oracle Solaris 11.3 for a discussion of Kerberos authentication.

If Kerberos V5 authentication is not enabled, then the authentication procedure follows the standard rlogin protocol:

  • The server checks the client's source port. If the port is not in the range 512-1023, the server aborts the connection.

  • The server checks the client's source address. If an entry for the client exists in both /etc/hosts and /etc/hosts.equiv, a user logging in from the client is not prompted for a password. If the address is associated with a host for which no corresponding entry exists in /etc/hosts, the user is prompted for a password, regardless of whether or not an entry for the client is present in /etc/hosts.equiv. See hosts(4) and hosts.equiv(4).

Once the source port and address have been checked, in.rlogind allocates a pseudo-terminal and manipulates file descriptors so that the slave half of the pseudo-terminal becomes the stdin, stdout, and stderr for a login process. The login process is an instance of the login(1) program, invoked with the –r.

The login process then proceeds with the pam(3PAM) authentication process. See SECURITY below. If automatic authentication fails, it reprompts the user to login.

The parent of the login process manipulates the master side of the pseudo-terminal, operating as an intermediary between the login process and the client instance of the rlogin program. In normal operation, a packet protocol is invoked to provide Ctrl-S and Ctrl-Q type facilities and propagate interrupt signals to the remote programs. The login process propagates the client terminal's baud rate and terminal type, as found in the environment variable, TERM.


The following options are supported:


Same as –k, for backwards compatibility.


Requires Kerberos V5 clients to present a cryptographic checksum of initial connection information like the name of the user that the client is trying to access in the initial authenticator. This checksum provides additionl security by preventing an attacker from changing the initial connection information. This option is mutually exclusive with the –i option.


Creates an encrypted session.


Same as –e, for backwards compatibility.


Ignores authenticator checksums if provided. This option ignores authenticator checksums presented by current Kerberos clients to protect initial connection information. Option –i is the opposite of option –c.


Allows Kerberos V5 authentication with the .k5login access control file to be trusted. If this authentication system is used by the client and the authorization check is passed, then the user is allowed to log in.

–M realm

Uses the indicated Kerberos V5 realm. By default, the daemon will determine its realm from the settings in the krb5.conf(4) file.


Prompts for authentication only if other authentication checks fail.


Prompts for a password in addition to other authentication methods.

–s tos

Sets the IP TOS option.

–S keytab

Sets the KRB5 keytab file to use. The/etc/krb5/krb5.keytab file is used by default.


Same as –e, for backwards compatibility.


Same as –e, for backwards compatibility.


rlogind and in.rlogind are IPv6–enabled. See ip6(7P). IPv6 is not currently supported with Kerberos V5 authentication.

Typically, Kerberized rlogin service runs on port 543 (klogin) and Kerberized, encrypted rlogin service runs on port 2105 (eklogin). The corresponding FMRI entries are:

svc:/network/login:klogin (rlogin with kerberos)
svc:/network/login:eklogin (rlogin with kerberos and encryption)


in.rlogind 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.rlogind. Here is a partial pam.conf file with entries for the rlogin command using the rhosts and UNIX authentication modules, and the UNIX account, session management, and password management modules.

auth sufficient
auth requisite
auth required
auth required
account required
account required
account required
session required

The equivalent PAM configuration using /etc/pam.d/ would be the following entries in /etc/pam.d/rlogin:

auth sufficient    pam_rhosts_auth.so.1
auth requisite     pam_authtok_get.so.1
auth required      pam_dhkeys.so.1
auth required      pam_unix_auth.so.1

account required   pam_unix_roles.so.1
account required   pam_unix_projects.so.1
account required   pam_unix_account.so.1

session required   pam_unix_session.so.1

With this configuration, the server checks the client's source address. If an entry for the client exists in both /etc/hosts and /etc/hosts.equiv, a user logging in from the client is not prompted for a password. If the address is associated with a host for which no corresponding entry exists in /etc/hosts, the user is prompted for a password, regardless of whether or not an entry for the client is present in /etc/hosts.equiv. See hosts(4) and hosts.equiv(4).

When running a Kerberized rlogin service (with or without the encryption option), the pam service name that should be used is “krlogin”.

If there are no entries for the rlogin service, then the entries for the “other” service will be used. If multiple authentication modules are listed, then the user may be prompted for multiple passwords. Removing the pam_rhosts_auth.so.1 entry will disable the /etc/hosts.equiv and ~/.rhosts authentication protocol and the user would always be forced to type the password. The sufficient flag indicates that authentication through the pam_rhosts_auth.so.1 module is sufficient to authenticate the user. Only if this authentication fails is the next authentication module used.


See attributes(5) for descriptions of the following attributes:

Interface Stability

See Also

login(1), svcs(1), rlogin(1), in.rshd(1M), inetadm(1M), inetd(1M), kadmin(1M), svcadm(1M), pam(3PAM), hosts(4), hosts.equiv(4), krb5.conf(4), pam.conf(4), attributes(5), environ(5), krb5_auth_rules(5), pam_authtok_check(5), pam_authtok_get(5), pam_authtok_store(5), pam_dhkeys(5), pam_passwd_auth(5), pam_unix_account(5), pam_unix_auth(5), pam_unix_session(5), smf(5)

Securing Systems and Attached Devices in Oracle Solaris 11.3


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.

Hostname for your address unknown.

No entry in the host name database existed for the client's machine.

Try again.

A fork by the server failed.

/usr/bin/sh: . . .

The user's login shell could not be started.


The authentication procedure used here assumes the integrity of each client machine and the connecting medium. This is insecure, but it is useful in an ``open'' environment.

A facility to allow all data exchanges to be encrypted should be present.

The in.rlogind service is managed by the service management facility, smf(5), under the service identifier:

svc:/network/login:rlogin (rlogin)
svc:/network/login:klogin (rlogin with kerberos)
svc:/network/login:eklogin (rlogin with kerberos and encryption)

Administrative actions on this service, such as enabling, disabling, or requesting restart, can be performed using svcadm(1M). Responsibility for initiating and restarting this service is delegated to inetd(1M). Use inetadm(1M) 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.