Which Of The Following Linux Commands Replaces The Rlogin And Rsk Services For Remote Logins?

Suite of remote-admission utilities

Berkeley r-commands
Developer(due south)	Computer Systems Research Grouping at the University of California, Berkeley
Initial release	June 1981; 40 years ago (1981-06)
Operating system	Unix and Unix-like
Type	Command suite
License	BSD

The Berkeley r-commands are a suite of calculator programs designed to enable users of one Unix system to log in or event commands to another Unix figurer via TCP/IP estimator network.^[i] The r-commands were developed in 1982 by the Estimator Systems Research Group at the University of California, Berkeley, based on an early implementation of TCP/IP (the protocol stack of the Internet).^[2]

The CSRG incorporated the r-commands into their Unix operating system, the Berkeley Software Distribution (BSD). The r-commands premiered in BSD v4.one.^[2] Among the programs in the suite are: rcp (remote copy), rexec (remote execution), rlogin (remote login), rsh (remote beat out), rstat, ruptime, and rwho (remote who).^[ii] ^[iii]

The r-commands were a pregnant innovation, and became de facto standards for Unix operating systems.^[4] ^[5] With wider public adoption of the Internet, their inherent security vulnerabilities became a trouble,^[6] and start with the evolution of Secure Beat protocols and applications in 1995, its adoption entirely supplanted the deployment and use of r-commands (and Telnet) on networked systems.^[7]

Hallmark [edit]

Overview
Service		Port	Transport	Refs
Client	Daemon	Port	Transport	Refs
rcp	rshd	514	TCP
rexec	rexecd	512	TCP	^[8]
rlogin	rlogind	513	TCP	^[9]
rsh	rshd	514	TCP
rstat	rstatd		UDP
ruptime	rwhod	513	UDP	^[x]
rwho	rwhod	513	UDP	^[9] ^[10]

This section needs expansion. You can help by calculation to it. (March 2018)

The original Berkeley parcel that provides rlogin likewise features rcp (remote-re-create, assuasive files to be copied over the network) and rsh (remote-crush, allowing commands to be run on a remote automobile without the user logging into it). These share the hosts.equiv and .rhosts admission-command scheme (although they connect to a different daemon, rshd).

Commands [edit]

rlogin [edit]

rlogin enables a user to log in on another server via estimator network, using TCP network port 513.

rlogin is besides the name of the awarding layer protocol used by the software, office of the TCP/IP protocol suite. Authenticated users tin human activity as if they were physically present at the figurer. RFC 1282, in which it was defined, states: "The rlogin facility provides a remote-echoed, locally flow-controlled virtual final with proper flushing of output." rlogin communicates with a daemon, rlogind, on the remote host. rlogin is similar to the Telnet control, but is non as customizable and is able to connect only to Unix-like hosts.

rsh [edit]

rsh opens a trounce on a remote figurer without a login procedure. In one case connected, the user tin execute commands on the remote computer through the shell's control-line interface. rsh passes input and output through the standard streams, and information technology sends standard output to the user'south console. Over the network, standard input and standard out menses through TCP port 514, while Standard Error flows through a different TCP port, which the rsh daemon (rshd) opens.^[11]

rexec [edit]

Like rsh, rexec enables the user to run vanquish commands on a remote estimator. Yet, dissimilar the rsh server, the rexec server (rexecd) requires login: it authenticates users by reading the username and countersign (unencrypted) from the network socket.^[12] rexec uses TCP port 512.

rcp [edit]

rcp can copy a file or directory from the local arrangement to a remote system, from a remote arrangement to the local system, or from one remote system to another.^[13] The command line arguments of cp and rcp are similar, only in rcp remote files are prefixed with the name of the remote organization:

rcp file.txt subdomain.domain:~/habitation/foo/file.txt

As with the Unix re-create command cp, rcp overwrites an existing file of the same name in the target; dissimilar cp, information technology provides no mechanism for warning the user before overwriting the target file.^[13] Like rsh, rcp uses TCP port 514.^[14]

rwho [edit]

Only equally the who control lists the users who are logged in to the local Unix system, rwho lists those users who are logged into all multi-user Unix systems on the local network.^[fifteen] rwho's daemon, rwhod, maintains a database of the status of Unix systems on the local network. The daemon and its database are besides used by the ruptime program.^[16]

rstat [edit]

rstat returns operation statistics from the kernel.

ruptime [edit]

Just as the uptime command shows how long a Unix system has been running since the last restart, ruptime requests a status report from all computers on the local network. It then returns the uptime report. If a computer did not respond within the time limit, so ruptime reports that the organization is downwards.^[17] This data is tracked and stored by the daemon rwhod, which is also used past the rwho command.^[16]

Security [edit]

Those r-commands which involve user hallmark (rcp, rexec, rlogin, and rsh) share several serious security vulnerabilities:

All information, including passwords, is transmitted unencrypted (making it vulnerable to interception).
The .rlogin (or .rhosts) file is piece of cake to misuse. They are designed to permit logins without a countersign, just their reliance on remote usernames, hostnames, and IP addresses is exploitable. For this reason many corporate system administrators prohibit .rhosts files, and actively scrutinize their networks for offenders.
The protocol partly relies on the remote party's rlogin client to provide data honestly, including source port and source host proper noun. A decadent client is thus able to forge this and gain access, as the rlogin protocol has no means of authenticating other machines' identities, or ensuring that the requesting client on a trusted machine is the real rlogin client.
The common do of mounting users' home directories via NFS exposes rlogin to set on by ways of faux .rhosts files - this means that whatever of NFS's security faults automatically plague rlogin.

Due to these problems, the r-commands fell into relative disuse (with many Unix and Linux distributions no longer including them by default). Many networks that formerly relied on rlogin and telnet have replaced them with SSH and its rlogin-equivalent slogin.^[18] ^[19]

Notes [edit]

^ Horwitz, Jeff (2003) [2002]. "Using the Berkeley r-commands Without a Password". Unix Arrangement Management: Primer Plus. Sams Publishing. p. 339. ISBN978-0-672-32372-0 . Retrieved 2018-03-04 – via Google Books.
^ ^a ^b ^c McKusick, Marshall Kirk (1999). "20 Years of Berkeley Unix: From AT&T-Owned to Freely Redistributable". Open up Sources: Voices from the Open Source Revolution. O'Reilly & Associates. Section: "4.2BSD". ISBN978-1-56592-582-3 . Retrieved 2018-03-03 .
^ Pyles, James; Carrell, Jeffrey 50.; Tittel, Ed (2017). "Which IP Services Are Most Vulnerable?". Guide to TCP/IP: IPv6 and IPv4 (5th ed.). Cengage Learning. p. 659. ISBN978-1-305-94695-viii – via Google Books.
^ Casad (2008), p. 346
^ Negus, Christopher (2004-07-02). "Near "r" Commands". Red Hat Fedora Linux 2 Bible. Wiley. ISBN0-7645-5745-nine. OCLC 441918216. Retrieved 2018-03-04 .
^ "A Case Study of Using a Secure Network Layer Protocol". CiteSeerX10.one.1.178.8497.
^ https://nuance.harvard.edu/bitstream/handle/1/16781951/sshVsTelnetWeb3.pdf?sequence=one^{[ blank URL PDF ]}
^ "REXEC command—Execute a command on the remote host and receive the results on your local host". z/Os Communications Server: IP User's Guide and Commands. 2013 [1990]. Retrieved 2018-03-04 .
^ ^a ^b "More than on Ports". FreeBSD Network Administrators Guide . Retrieved 2018-03-04 .
^ ^a ^b Casad (2008), pp. 350–51
^ Edwards, Wade; Lancaster, Tom; Quinn, Eric; Rohm, Jason; Tow, Bryant (2004). CCSP: Secure PIX and Secure VPN Study Guide. Sybex. p. 154. ISBN0-7821-4287-7 . Retrieved 2018-03-07 – via Google Books.
^ "rexecd(8)". manpagez.com . Retrieved 2018-03-03 .
^ ^a ^b Farrell, Phillip (3 August 2004). "rcp". earthsci.stanford.edu. Stanford University School of Globe, Energy & Environmental Sciences. Retrieved 2018-03-06 .
^ "Rlogin, RSH, and RCP". SourceDaddy . Retrieved 2018-02-18 .
^ "rwho (ane) - Linux Homo Pages". Retrieved 2018-03-07 .
^ ^a ^b "rwhod (8) - Linux Man Pages". Retrieved 2018-03-07 .
^ "ruptime (one) - Linux Homo Pages". SysTutorials . Retrieved 2018-03-07 .
^ Sobell, Mark (2010). A Practical Guide to Linux Commands, Editors, and Shell Programming. Pearson Instruction, Inc. ISBN978-0-thirteen-136736-4.
^ "Unix job command command list". Indiana University. Retrieved 20 Dec 2014.

References [edit]

Casad, Joe (2008). "Berkeley Remote Utilities". Sams Teach Yourself TCP/IP in 24 Hours. Pearson Educational activity. ISBN978-0-13-271513-3 – via Google Books.

External links [edit]

RFC 1282, BSD Rlogin (1991)
rlogin(one) – Linux User Commands Manual
rlogin(1) : remote login – Darwin and macOS General Commands Transmission
rlogin(ane) : remote login – Solaris 10 User Commands Reference Manual