Content-type: text/html Man page of rlogin


Section: User Commands (1)
Updated: 9 Feb 2009
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rlogin - remote login  


rlogin [-8EL] [-ec ] [-A] [-K] [-x] [-PN | -PO] [-f | -F] [-a] 
     [-l username] [-k realm] hostname



The rlogin utility establishes a remote login session from your terminal to the remote machine named hostname. The user can choose to kerberize the rlogin session using Kerberos V5 and also protect the data being transferred.

Hostnames are listed in the hosts database, which may be contained in the /etc/hosts file, the Network Information Service (NIS) hosts map, the Internet domain name server, or a combination of these. Each host has one official name (the first name in the database entry), and optionally one or more nicknames. Either official hostnames or nicknames may be specified in hostname.

The user can opt for a secure rlogin session which uses Kerberos V5 for authentication. Encryption of the session data is also possible. The rlogin session can be kerberized using any of the following Kerberos specific options: -A, -PN or -PO, -x, -f or -F, and -k realm. Some of these options (-A, -x, -PN or -PO, and -f or -F) can also be specified in the [appdefaults] section of krb5.conf(4). The usage of these options and the expected behavior is discussed in the OPTIONS section below. If Kerberos authentication is used, authorization to the account is controlled through rules in krb5_auth_rules(5). If this authorization fails, fallback to normal rlogin using rhosts will occur only if the -PO option is used explicitly on the command line or is specified in krb5.conf(4). Also notice that the -PN or -PO, -x, -f or -F, and -k realm options are just supersets of the -A option.

The remote terminal type is the same as your local terminal type, as given in your environment TERM variable. The terminal or window size is also copied to the remote system if the server supports the option. Changes in size are reflected as well. All echoing takes place at the remote site, so that (except for delays) the remote login is transparent. Flow control using Control-S and Control-Q and flushing of input and output on interrupts are handled properly.  


The following options are supported:


Passes eight-bit data across the net instead of seven-bit data.


Forces the remote machine to ask for a password by sending a null local username.


Explicitly enables Kerberos authentication and trusts the .k5login file for access-control. If the authorization check by in.rlogind(1M) on the server-side succeeds and if the .k5login file permits access, the user is allowed to login without supplying a password.


Specifies a different escape character, c, for the line used to disconnect from the remote host.


Stops any character from being recognized as an escape character.


Forwards a copy of the local credentials (Kerberos Ticket Granting Ticket) to the remote system. This is a non-forwardable ticket granting ticket. You must forward a ticket granting ticket if you need to authenticate yourself to other Kerberized network services on the remote host. An example is if your home directory on the remote host is NFS mounted via Kerberos V5. If your local credentials are not forwarded in this case, you will not be able to access your home directory. This option is mutually exclusive with the -F option.


Forwards a forwardable copy of the local credentials (Kerberos Ticket Granting Ticket) to the remote system. The -F option provides a superset of the functionality offered by the -f option. For example, with the -f option, after you connected to the remote host, any attempt to invoke /usr/bin/ftp, /usr/bin/telnet, /usr/bin/rlogin, or /usr/bin/rsh with the -f or -F options would fail. Thus, you would be unable to push your single network sign on trust beyond one system. This option is mutually exclusive with the -f option.

-k realm

Causes rlogin to obtain tickets for the remote host in realm instead of the remote host's realm as determined by krb5.conf(4).


This option explicitly disables Kerberos authentication. It can be used to override the autologin variable in krb5.conf(4).

-l username

Specifies a different username for the remote login. If you do not use this option, the remote username used is the same as your local username.


Allows the rlogin session to be run in "litout" mode.


Explicitly requests the new (-PN) or old (-PO) version of the Kerberos `rcmd' protocol. The new protocol avoids many security problems prevalant in the old one and is considered much more secure, but is not interoperable with older (MIT/SEAM) servers. The new protocol is used by default, unless explicitly specified using these options or by using krb5.conf(4). If Kerberos authorization fails when using the old `rcmd' protocol, there is fallback to regular, non-kerberized rlogin. This is not the case when the new, more secure `rcmd' protocol is used.


Turns on DES encryption for all data passed through the rlogin session. This reduces response time and increases CPU utilization.


Escape Sequences

Lines that you type which start with the tilde character (~) are "escape sequences." The escape character can be changed using the -e option.


Disconnects from the remote host. This is not the same as a logout, because the local host breaks the connection with no warning to the remote end.


Suspends the login session, but only if you are using a shell with Job Control. susp is your "suspend" character, usually Control-Z. See tty(1).


Suspends the input half of the login, but output will still be seen (only if you are using a shell with Job Control). dsusp is your "deferred suspend" character, usually Control-Y. See tty(1).




The remote machine on which rlogin establishes the remote login session.



For the kerberized rlogin session, each user may have a private authorization list in a file, .k5login, in his home directory. Each line in this file should contain a Kerberos principal name of the form principal/[email protected]. If there is a ~/.k5login file, access is granted to the account if and only if the originating user is authenticated to one of the principals named in the ~/.k5login file. Otherwise, the originating user will be granted access to the account if and only if the authenticated principal name of the user can be mapped to the local account name using the authenticated-principal-namelocal-user-name mapping rules. The .k5login file (for access control) comes into play only when Kerberos authentication is being done.

For the non-secure rlogin session, each remote machine may have a file named /etc/hosts.equiv containing a list of trusted host names with which it shares user names. Users with the same user name on both the local and remote machine may rlogin from the machines listed in the remote machine's /etc/hosts.equiv file without supplying a password. Individual users may set up a similar private equivalence list with the file .rhosts in their home directories. Each line in this file contains two names, that is, a host name and a user name, separated by a space. An entry in a remote user's .rhosts file permits the user named username who is logged into hostname to log in to the remote machine as the remote user without supplying a password. If the name of the local host is not found in the /etc/hosts.equiv file on the remote machine, and the local user name and host name are not found in the remote user's .rhosts file, then the remote machine will prompt for a password. Host names listed in the /etc/hosts.equiv and .rhosts files must be the official host names listed in the hosts database. Nicknames may not be used in either of these files.

For security reasons, the .rhosts file must be owned by either the remote user or by root.  



Contains information about users' accounts.


For hostname version of the command.


List of trusted hostnames with shared user names.


Message displayed to users attempting to login during machine shutdown.


Private list of trusted hostname/username combinations.


File containing Kerberos principals that are allowed access.


Kerberos configuration file.


Hosts database.



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





rsh(1), stty(1), tty(1), in.rlogind(1M), hosts(4),hosts.equiv(4), krb5.conf(4), nologin(4), attributes(5), krb5_auth_rules(5)  


The following message indicates that the machine is in the process of being shutdown and logins have been disabled:

NO LOGINS: System going down in N minutes



When a system is listed in hosts.equiv, its security must be as good as local security. One insecure system listed in hosts.equiv can compromise the security of the entire system.

The Network Information Service (NIS) was formerly known as Sun Yellow Pages (YP.) The functionality of the two remains the same. Only the name has changed.

This implementation can only use the TCP network service.



Escape Sequences

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Time: 02:39:24 GMT, October 02, 2010