Sync Time using NTP

Most servers are probably automatically configured to network time, but if you want to set it up for yourself, or want to change the servers that you are syncing to, here’s the quick article that shows you how to do it.

Since I had to do this earlier today, I decided it would make a lot of sense to write it down for the next time that I need to do it. Yeah, this article is really just for me.

First, you’ll need to install NTP if it isn’t already installed. For Debian or Ubuntu, that would be this command:

sudo apt-get install ntp

For Redhat or CentOS, you’ll need to use this one:

yum install ntp

Then you’ll want to edit the /etc/ntp.conf file, which is quite possibly already filled out for you.

vi /etc/ntp.conf

You’ll find a lot of lines in there, but the important ones are the server lines. You can get a list of server addresses at www.pool.ntp.org, find the preferred ones for your area, and then add them to the file. For my purposes, that meant:

server 0.north-america.pool.ntp.org
server 1.north-america.pool.ntp.org
server 2.north-america.pool.ntp.org
server 3.north-america.pool.ntp.org

Then you’ll need to restart or start the NTPD service:

/etc/init.d/ntpd restart

If you want to update the time right now, you can stop the NTP service and then run the following command, swapping out your preferred server for pool.ntp.org.

/usr/sbin/ntpdate pool.ntp.org

Increase the size of /dev/shm

To increase the size of /dev/shm for oracle, please perform below steps

Add entry like below on /etc/fstab to make /dev/shm size 10GB

udev        /dev/shm   tmpfs          noauto,size=10g       0 0

Unmount and mount /dev/shm or reboot the server .

umount /dev/shm
mount /dev/shm

Check the size of /dev/shm

lnxsrv:~ # df -h /dev/shm
Filesystem      Size  Used Avail Use% Mounted on
udev             10G     0   10G   0% /dev/shm
lnxsrv:~ #

Extending Swap on an LVM2 Logical Volume

To extend an LVM2 swap logical volume (assuming /dev/VolGroup00/LogVol01 is the volume you want to extend):


Disable swapping for the associated logical volume:
# swapoff -v /dev/VolGroup00/LogVol01
Resize the LVM2 logical volume by 256 MB:
# lvm lvresize /dev/VolGroup00/LogVol01 -L +256M
Format the new swap space:
# mkswap /dev/VolGroup00/LogVol01
Enable the extended logical volume:
# swapon -va
Test that the logical volume has been extended properly:
# cat /proc/swaps # free

HOW CAN I DISABLE THE FIREWALL ON SLES ?

HOW CAN I DISABLE THE FIREWALL ON SLES?

Believe it or not, there are valid reasons why you might want to disable the firewall service on a Suse Linux Enterprise Server (SLES).  For instance, avoiding NCP time-outs on client connections for an OES/SLES server.  If you just want to know how to disable the firewall in most modern incarnations of SLES, read on…

The examples given here are assuming you are remote to the server.  Of course, you could do all of this locally on the console, or adapt my instructions to the gui “Yast2″, but I’m going non-gui here for simplicity.

First, shell into the box, and su to root.

METHOD 1:

Launch the Yast non-gui firewall module:
yast firewall

To change to startup setting to “Manually”:
“Alt + m”

Optionally, to stop the service right now if running:
“Alt + t”

To complete the change:
“Alt + n”

To accept and finish:
“Alt + a”

METHOD 2:

To disable the service at next startup:
chkconfig SuSEfirewall2_setup off
chkconfig SuSEfirewall2_init off

Optionally, to stop the service right now if running:
rcSuSEfirewall2 stop