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===ruptime===
Just as the {{code|uptime}} command shows how long a Unix system has been running since the last restart, {{code|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, then ruptime reports that the system is [[Downtime|down]].<ref>{{cite web |url=https://www.systutorials.com/docs/linux/man/1-ruptime/ |title=ruptime (1) - Linux Man Pages |website=SysTutorials |access-date=2018-03-07}}</ref> This information is tracked and stored by the daemon rwhod, which is also used by the rwho command.<ref name="syst_rwhod"/>
== Security ==
Those r-commands which involve user authentication (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 easy to misuse. They are designed to allow logins without a [[password]], but 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 information honestly, including source port and source host name. A corrupt client is thus able to forge this and gain access, as the rlogin protocol has no means of [[Authentication|authenticating]] other machines' identities, or ensuring that the requesting client on a trusted machine is the real rlogin client.
* The common practice of mounting users' home directories via NFS exposes rlogin to attack by means of fake .rhosts files - this means that any of [[Network File System|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 [[Secure shell|SSH]] and its rlogin-equivalent ''slogin''.<ref name="Sobell">{{cite book|last=Sobell|first=Mark|title=A Practical Guide to Linux Commands, Editors, and Shell Programming|ISBN=978-0-13-136736-4|date=2010|publisher=Pearson Education, Inc}}</ref><ref name="iu">{{cite web|title=Unix job control command list|publisher=Indiana University|url=https://kb.iu.edu/d/afnw|accessdate=20 December 2014}}</ref>
== See also ==
* [[List of Unix commands]]
==Notes==
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