Posted by: h4ck@lyst | September 19, 2008

init 1

Linux systems provide 10 runlevels, from 0 to 9. Conventionally only seven, from 0-6 are used though.

init 0 halts the system while init 6 reboots the system. Init 1 runs the system with most basic of the services. Now init 1 is something that I used to think can be used only for system maintenance and no real work. But that perception of mine changed today. You can run the entire webserver in init 1. Today one of our internal servers “delta” had some problem with its message bus daemon. Messagebus in turns calls dbus-daemon.

From http://www.freedesktop.org/wiki/Software/dbus

D-Bus is a message bus system, a simple way for applications to talk to one another. In addition to interprocess communication, D-Bus helps coordinate process lifecycle; it makes it simple and reliable to code a “single instance” application or daemon, and to launch applications and daemons on demand when their services are needed.

Ok, so there was some problem starting this messagebus service and as this service was configured in init 2,3,5, the system won’t boot completely but rather be stuck at starting messagebus :(. This is a fedora 9 server as of now! I waited for as long as a couple of hours for it to start but it simply wont. And other time it will just start off as if nothing had happened!

Anyways, so we needed the server urgently in the morning coz festember billing system is hosted on delta. I then started the system in single user mode. Then went to init 1 to see if something can be done. I started sshd, network, httpd and mysqld services. And voila, the webservices of delta were up and running. And we could also use the entire services of delta using ssh -XCYP!

wow! So as much as I can understand, runlevels only define the default services that will be started. It doesnt hamper any other aspect of the system.Only the ldap users are not accessible as of now 😦

Hail init 1!

Other things that I did while trying to start the messagebus. I actually edited the init files! System files that I would normally not even think of editing. But thats the power of linux. It lets you do any and everything as long as you know what you want and what you need to do 🙂

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