What Linux run level am I in?

For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))

Linux / Unix systems have a "run level" that they're in ...
0 - halted
1 - single user
2 - multiuser (client)
3 - full multiuser
5 - full multiuser with X windows running
6 - reboot

How do I find out what run level a system is in at the moment? - a question asked on today's Java course (OK - it was over lunch and we were ~~a bit~~ a lot off topic ...)

1. The runlevel command tells you what run level you are in

2. The who -r command also tells you the run level, together with some other information.

Here's a machine which is in full multiuser mode, running as a server:

[trainee@melksham ~]$ /sbin/runlevel

N 3

[trainee@melksham ~]$ who -r

         run-level 3  2009-05-15 09:28                   last=S

[trainee@melksham ~]$

And here's one which is in full multiuser mode and has the windows system running too ...

[trainee@easterton ~]$ /sbin/runlevel

N 5

[trainee@easterton ~]$ who -r

         run-level 5  2009-05-15 15:04                   last=S

[trainee@easterton ~]$

Notes:

1. The runlevel command is intended for administrators only, so is in the sbin directory which is not on the normal user's path. However, the command is purely information so is available to all users who know where to find it.

2. The default run level of a system can be changed by updating the /etc/inittab file ... the line
id:5:initdefault:
will bring the system up into run state 5 on startup / reboot. Change the 5 to a 3 if you want the machine to start / reboot into run state 3

3. It is strongly recommended that you do not run your web servers in run state 5 ... I have had instances on a course where delegates have complained about a slow server, and they have been amazed when I have walked up to a 'spare' machine, moved the mouse around, and asked if the performance has improved. They have been even more amazed to be able to confirm that it HAS made a difference. What had happened? The system was running a screen saver in X Windows ... and it was eating up all the cpu resource in keeping an "atlantis" display of 3D whales and sharks swimming around the screen. Moving the mouse cancelled the screen saver ... and released the resources back to the server

4. Rather obviously, runlevel cannot report that a machine is in run state 0!
(written 2009-05-15)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles

A164 - Web Application Deployment - Services and Regular Jobs
  [544] Repeating tasks with crontab - (2005-12-27)
  [907] Browser -> httpd -> Tomcat -> MySQL. Restarting. - (2006-10-28)
  [1028] Linux / Unix - process priority and nice - (2007-01-10)
  [1288] Linux run states, shell special commands, and directory structures - (2007-08-03)
  [1553] Automatic startup and shutdown of Tomcat - (2008-02-24)
  [1633] Changing a screen saver from a web page (PHP, Perl, OSX) - (2008-05-06)
  [1700] FTP server on Fedora Linux - (2008-07-06)
  [1731] Apache httpd, MySQL, PHP - installation procedure - (2008-08-01)
  [1733] memcached - overview, installation, example of use in PHP - (2008-08-02)
  [1765] Dialects of English and Unix - (2008-08-21)
  [1903] daemons - what is running on my Linux server? - (2008-11-23)
  [2145] Using the internet to remotely check for power failure at home (PHP) - (2009-04-29)
  [3011] What are .pid files? - (2010-10-23)
  [3143] On time - (2011-01-23)
  [3791] The Kernel, Shells and Daemons. Greek Gods in computing - (2012-07-01)
  [3792] Managing daemons from a terminal session - (2012-07-01)
  [4487] Starting MySQL. ERROR! The server quit without updating PID file - how we fixed it. - (2015-05-06)

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Servlet life cycle, and Java Servlet variable scope

Some other Articles

An FAQ on the Apache httpd and Apache Tomcat web servers, and on using them together
Abstract Classes - Java
Choosing the right version of Java and Tomcat
Servlet life cycle, and Java Servlet variable scope
What Linux run level am I in?
You cannot please all of the people all of the time
Patterns in numbers - room occupancy
Offers that I can refuse
Melksham Candidates for Wiltshire Unitary Election
Preventing forum spam - checks at sign up

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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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