/dev/shm

749851.1

MEMORY_TARGET or MEMORY_MAX_TARGET, cannot be greater than the shared memory filesystem (/dev/shm).

The AMM and HugePages are not compatible. One needs to disable AMM on 11g to be able to use HugePages. See Note 749851.1 for further information.

/dev/shm is nothing but implementation of traditional shared memory concept. It is an efficient means of passing data between programs. One program will create a memory portion, which other processes (if permitted) can access. This will result into speeding up things on Linux.

For example, if you have 8GB RAM then remount /dev/shm as follows:
# mount -o remount,size=8G /dev/shm

cluvfy samples

./olsnodes -n

./cluvfy stage -pre crsinst -n node1,node2,node3 -r 11gr1 -verbose >cluvfy_pre.txt

./cluvfy stage -post crsinst -n node1,node2,node3 -verbose > cluvfy_post.txt


./cluvfy stage -post hwos -n node1,node2,node3 -verbose >cluvfy_hwos.txt
--Above display NIC cards subnet info, very useful.
--Storage check may fail for non scci disk e.g EMC etc, that can be ignored as per metalink note#!

"-n all "can be specified for all nodes instead of listing every node.

ifconfig help

ifconfig eth0

View the network settings on the first Ethernet adapter installed in the computer.

ifconfig -a

Display info on all network interfaces on server, active or inactive.

ifconfig eth0 down

If eth0 exists would take it down causing it cannot send or receive any information.

ifconfig eth0 up

If eth0 exists and in the down state would return it back to the up state allowing to to send and receive information.

ifconfig eth0 192.168.1.102 netmask 255.255.255.0 broadcast 192.168.1.255

Assign eth0 with the above values for IP, netmask and broadcast address.

Changing IP or Hostname on Linux

--Linux/OS Installation

IP=10.224.8.151
Subnet Mask=255.255.255.0
Gateway=10.224.8.1

Domain=abc.com
DNS=10.224.8.126
         10.224.8.120

Make sure IP is unused.

Below show IP address associated with eth0(which is primary NIC card)

# ifconfig eth0

Below shows default gateway

# route -n

To Change IP
================

Bringing down a network interface with ifconfig

# ifconfig eth0 down

Bringing up an Ethernet interface with ifconfig

# ifconfig eth0 192.168.99.14 netmask 255.255.255.0 up

Setting the Default Route

# route add default gw 192.168.99.254


To Change Hostnme
===================

Backup and edit the the file /etc/sysconfig/network

HOSTNAME=.

this will be available after a reboot.

a quicker way, in memory change is- edit

Backup and Edit the file /proc/sys/kernel/hostname.

but that won't be saved when you reboot.

Fixing bad fstab entries

How modify fstab when its 'ro' in "repair filesystem" mode ?

When Logged in as "Repair Filesystem" mode at console, by default "/" filessystem is READ only mode.

Remount "/" filesystem with RW option.

# mount -o remount,rw /


Then backup and edit /etc/fstab file for any wrong entries and reboot system again

#init 6

Linux init commands(To bounce server)

Init RUnlevels
====================

0        -        halt
1        -        Single user mode
2        -        Multiuser, without NFS (The same as 3, if you don't have networking)
3        -        Full multiuser mode
4        -        unused
5        -        X11
6        -        Reboot

to Reboot

#init 6

to Shutdown

# init 0

Mount CDROM in Linux

To mount CDROM on Linux

Use following command

Make sure /cdrom folder is available.

# mount -t iso9660 -o ro /dev/cdrom /cdrom