||Home||Switchboard||Unix Administration||Red Hat||TCP/IP Networks||Neoliberalism||Toxic Managers|
|(slightly skeptical) Educational society promoting "Back to basics" movement against IT overcomplexity and bastardization of classic Unix|
login - sign on
login [ name ]
login -h hostname
login -f name
login is used when signing onto a system. It can also be used to control who can login to the system.
If an argument is not given, login prompts for the username.
If the user is not root, and if /etc/nologin exists, the contents of this file are printed to the screen, and the login is terminated. This is typically used to prevent logins when the system is being taken down.
If special access restrictions are specified for the user in /etc/usertty, these must be met, or the log in attempt will be denied and a syslog message will be generated. See the section on "Special Access Restrictions".
If the user is root, then the login must be occurring on a tty listed in /etc/securetty. Failures will be logged with the syslog facility.
After these conditions have been checked, the password will be requested and checked (if a password is required for this username). Ten attempts are allowed before login dies, but after the first three, the response starts to get very slow. Login failures are reported via the syslog facility. This facility is also used to report any successful root logins.
If the file .hushlogin exists, then a "quiet" login is performed (this disables the checking of mail and the printing of the last login time and message of the day). Otherwise, if /var/log/lastlog exists, the last login time is printed (and the current login is recorded).
Random administrative things, such as setting the UID and GID of the tty are performed. The TERM environment variable is preserved, if it exists (other environment variables are preserved if the -p option is used). Then the HOME, PATH, SHELL, TERM, MAIL, and LOGNAME environment variables are set. PATH defaults to /usr/local/bin:/bin:/usr/bin for normal users, and to /usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin for root. Last, if this is not a "quiet" login, the message of the day is printed and the file with the user's name in /var/spool/mail will be checked, and a message printed if it has non-zero length.
The user's shell is then started. If no shell is specified for the user in /etc/passwd, then /bin/sh is used. If there is no directory specified in /etc/passwd, then / is used (the home directory is checked for the .hushlogin file described above).
Used by getty(8) to tell login not to destroy the environment
Used to skip a second login authentication. This specifically does not work for root, and does not appear to work well under Linux.
Used by other servers (i.e., telnetd(8)) to pass the name of the remote host to login so that it may be placed in utmp and wtmp. Only the superuser may use this option.
The file /etc/securetty lists the names of the ttys where root is allowed to log in. One name of a tty device without the /dev/ prefix must be specified on each line. If the file does not exist, root is allowed to log in on any tty.
On most modern Linux systems PAM (Pluggable Authentication Modules) is used. On systems that do not use PAM, the file /etc/usertty specifies additional access restrictions for specific users. If this file does not exist, no additional access restrictions are imposed. The file consists of a sequence of sections. There are three possible section types: CLASSES, GROUPS and USERS. A CLASSES section defines classes of ttys and hostname patterns, A GROUPS section defines allowed ttys and hosts on a per group basis, and a USERS section defines allowed ttys and hosts on a per user basis.
Each line in this file in may be no longer than 255 characters. Comments start with # character and extend to the end of the line.
The word at the beginning of a line becomes defined as a collective name for the ttys and host patterns specified at the rest of the line. This collective name can be used in any subsequent GROUPS or USERS section. No such class name must occur as part of the definition of a class in order to avoid problems with recursive classes.
An example CLASSES section:
CLASSES myclass1 tty1 tty2 myclass2 tty3 @.foo.comThis defines the classes myclass1 and myclass2 as the corresponding right hand sides.
A GROUPS section starts with the word GROUPS in all upper case at the start of a line, and each following line is a sequence of words separated by spaces or tabs. The first word on a line is the name of the group and the rest of the words on the line specifies the ttys and hosts where members of that group are allowed access. These specifications may involve the use of classes defined in previous CLASSES sections.
An example GROUPS section.
GROUPS sys tty1 @.bar.edu stud myclass1 tty4This example specifies that members of group sys may log in on tty1 and from hosts in the bar.edu domain. Users in group stud may log in from hosts/ttys specified in the class myclass1 or from tty4.
An example USERS section:
USERS zacho tty1 @126.96.36.199/255.255.255.0 blue tty3 myclass2This lets the user zacho login only on tty1 and from hosts with IP addreses in the range 188.8.131.52 - 184.108.40.206, and user blue is allowed to log in from tty3 and whatever is specified in the class myclass2.
There may be a line in a USERS section starting with a username of *. This is a default rule and it will be applied to any user not matching any other line.
If both a USERS line and GROUPS line match a user then the user is allowed access from the union of all the ttys/hosts mentioned in these specifications.
o The string @localhost, meaning that the user is allowed to telnet/rlogin from the local host to the same host. This also allows the user to for example run the command: xterm -e /bin/login.
o A domain name suffix such as @.some.dom, meaning that the user may rlogin/telnet from any host whose domain name has the suffix .some.dom.
o A range of IPv4 addresses, written @x.x.x.x/y.y.y.y where x.x.x.x is the IP address in the usual dotted quad decimal notation, and y.y.y.y is a bitmask in the same notation specifying which bits in the address to compare with the IP address of the remote host. For example @220.127.116.11/255.255.254.0 means that the user may rlogin/telnet from any host whose IP address is in the range 18.104.22.168 - 22.214.171.124.Any of the above origins may be prefixed by a time specification according to the syntax:
timespec ::= '[' <day-or-hour> [':' <day-or-hour>]* ']' day ::= 'mon' | 'tue' | 'wed' | 'thu' | 'fri' | 'sat' | 'sun' hour ::= '0' | '1' | ... | '23' hourspec ::= <hour> | <hour> '-' <hour> day-or-hour ::= <day> | <hourspec>For example, the origin [mon:tue:wed:thu:fri:8-17]tty3 means that log in is allowed on mondays through fridays between 8:00 and 17:59 (5:59 pm) on tty3. This also shows that an hour range a-b includes all moments between a:00 and b:59. A single hour specification (such as 10) means the time span between 10:00 and 10:59.
Not specifying any time prefix for a tty or host means log in from that origin is allowed any time. If you give a time prefix be sure to specify both a set of days and one or more hours or hour ranges. A time specification may not include any white space.
If no default rule is given then users not matching any line /etc/usertty are allowed to log in from anywhere as is standard behavior.
/var/run/utmp /var/log/wtmp /var/log/lastlog /var/spool/mail/* /etc/motd /etc/passwd /etc/nologin /etc/usertty .hushlogin
init(8), getty(8), mail(1), passwd(1), passwd(5), environ(7), shutdown(8)
The undocumented BSD -r option is not supported. This may be required by some rlogind(8) programs.
A recursive login, as used to be possible in the good old days, no longer works; for most purposes su(1) is a satisfactory substitute. Indeed, for security reasons, login does a vhangup() system call to remove any possible listening processes on the tty. This is to avoid password sniffing. If one uses the command "login", then the surrounding shell gets killed by vhangup() because it's no longer the true owner of the tty. This can be avoided by using "exec login" in a top-level shell or xterm.
Derived from BSD login 5.40 (5/9/89) by Michael Glad ([email protected])
Ported to Linux 0.12: Peter Orbaek ([email protected])
Groupthink : Two Party System as Polyarchy : Corruption of Regulators : Bureaucracies : Understanding Micromanagers and Control Freaks : Toxic Managers : Harvard Mafia : Diplomatic Communication : Surviving a Bad Performance Review : Insufficient Retirement Funds as Immanent Problem of Neoliberal Regime : PseudoScience : Who Rules America : Neoliberalism : The Iron Law of Oligarchy : Libertarian Philosophy
War and Peace : Skeptical Finance : John Kenneth Galbraith :Talleyrand : Oscar Wilde : Otto Von Bismarck : Keynes : George Carlin : Skeptics : Propaganda : SE quotes : Language Design and Programming Quotes : Random IT-related quotes : Somerset Maugham : Marcus Aurelius : Kurt Vonnegut : Eric Hoffer : Winston Churchill : Napoleon Bonaparte : Ambrose Bierce : Bernard Shaw : Mark Twain Quotes
Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 : Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law
Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds : Larry Wall : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOS : Programming Languages History : PL/1 : Simula 67 : C : History of GCC development : Scripting Languages : Perl history : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history
The Peter Principle : Parkinson Law : 1984 : The Mythical Man-Month : How to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Haterís Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite
Most popular humor pages:
Manifest of the Softpanorama IT Slacker Society : Ten Commandments of the IT Slackers Society : Computer Humor Collection : BSD Logo Story : The Cuckoo's Egg : IT Slang : C++ Humor : ARE YOU A BBS ADDICT? : The Perl Purity Test : Object oriented programmers of all nations : Financial Humor : Financial Humor Bulletin, 2008 : Financial Humor Bulletin, 2010 : The Most Comprehensive Collection of Editor-related Humor : Programming Language Humor : Goldman Sachs related humor : Greenspan humor : C Humor : Scripting Humor : Real Programmers Humor : Web Humor : GPL-related Humor : OFM Humor : Politically Incorrect Humor : IDS Humor : "Linux Sucks" Humor : Russian Musical Humor : Best Russian Programmer Humor : Microsoft plans to buy Catholic Church : Richard Stallman Related Humor : Admin Humor : Perl-related Humor : Linus Torvalds Related humor : PseudoScience Related Humor : Networking Humor : Shell Humor : Financial Humor Bulletin, 2011 : Financial Humor Bulletin, 2012 : Financial Humor Bulletin, 2013 : Java Humor : Software Engineering Humor : Sun Solaris Related Humor : Education Humor : IBM Humor : Assembler-related Humor : VIM Humor : Computer Viruses Humor : Bright tomorrow is rescheduled to a day after tomorrow : Classic Computer Humor
The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D
Copyright © 1996-2021 by Softpanorama Society. www.softpanorama.org was initially created as a service to the (now defunct) UN Sustainable Development Networking Programme (SDNP) without any remuneration. This document is an industrial compilation designed and created exclusively for educational use and is distributed under the Softpanorama Content License. Original materials copyright belong to respective owners. Quotes are made for educational purposes only in compliance with the fair use doctrine.
FAIR USE NOTICE This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available to advance understanding of computer science, IT technology, economic, scientific, and social issues. We believe this constitutes a 'fair use' of any such copyrighted material as provided by section 107 of the US Copyright Law according to which such material can be distributed without profit exclusively for research and educational purposes.
This is a Spartan WHYFF (We Help You For Free) site written by people for whom English is not a native language. Grammar and spelling errors should be expected. The site contain some broken links as it develops like a living tree...
|You can use PayPal to to buy a cup of coffee for authors of this site|
Last modified: March, 12, 2019