Page 82 - DCAP602_NETWORK_OPERATING_SYSTEMS_I

Network Operating Systems-I

notes The rc program looks in the /etc/rc.d/rc3.d directory, executing any k* scripts (of which there
are none in the rc3.d directory) with an option of stop. Then, all the s* scripts are started with
an option of start. Scripts are started in numerical order—thus, the S10network script is started
before the S85httpd script. This allows you to choose exactly when your script starts without
having to edit files. The same is true of the k* scripts.
Let’s look at what happens when we switch runlevels—say from runlevel 3 (full networking and
multi-user mode) to runlevel 1 (single-user mode).
First, all the k* scripts in the level to which the system is changing are executed. My Caldera
Preview II (Red Hat 2.0) setup has seven K scripts and one S script in the /etc/rc.d/rc.1/
directory. The K scripts shut down nfs, sendmail, lpd, inet, cron, and syslog. The S script then
kills off any remaining programs and executes init -t1 s, which tells the system to really go into
single-user mode.
Once in single-user mode, you can switch back to full multi-user mode by typing init 3.

side-stepping init

There are two additional points I can make here.
First, you can selectively start and stop scripts, even those not native to your runlevel. Executing
scripts in /etc/rc.d/init.d/ with an option of start or stop will start up or stop the programs or
services which the script controls. This allows you to turn off NFS from runlevel 3 while keeping
all other systems active, for example. Similarly, you can start NFS back up when you are ready.
!
Caution Stopping NFS in this case would require stopping two systems—nfsfs and nfs.

The nfsfs script will mount or ummount any of the NFS-mounted file-systems listed in
your /etc/fstab. The nfs script would then shut down the processes associated with NFS,
in this case mountd and nfsd.
So the proper procedure for shutting down NFS would be:
# /etc/rc.d/init.d/nfsfs stop
Unmounting remote filesystems.
# /etc/rc.d/init.d/nfs stop

Shutting down NFS services: rpc.mountd rpc.nfsd
#
And starting NFS would be:

# /etc/rc.d/init.d/nfs start
Starting NFS services: rpc.mountd rpc.nfsd
# /etc/rc.d/init.d/nfsfs start
Mounting remote filesystems.
#

Task “The rc program looks in the /etc/rc.d/rc3.d directory, executing any K*
scripts.” Comment

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