Kernel Parameters:

Oracle recommends that you set shared memory segment attributes as well as semaphores to the following values.
If not set, database instance creation will fail. I added the following lines to /etc/sysctl.conf file. Every OS process needs
semaphore where It waits on for the resources. For more on semaphore, please read the UNIX os documents.
Oracle 10g RAC requires to have 1GB of RAM available on each node to sucessfully install 11g RAC. Well, I have
managed to install it with 512 MB RAM. You will get warning during checking of pre-requise step of installation
step which you can ignore. Please goto Adding an Extra Swapspace if you want to have an extra swapspace added.

 NOTE: If the current value for any parameter is higher than the value listed in this table, then do not change
              the value of that parameter.

                   To see the current setting in the kernel, please use the below command.

/sbin/sysctl -a | grep sem      -- for semmsl, semmns, semopm, semmni
/sbin/sysctl -a | grep shm      -- for shmall, shmmax, shmmni
/sbin/sysctl -a | grep file-max
/sbin/sysctl -a | grep ip_local_port_range
/sbin/sysctl -a | grep rmem_default

Please add/change the appropriate variables value in the /etc/sysctl.conf file as shown below.

[root@node2-pub ~]# cat /etc/sysctl.conf
# Kernel sysctl configuration file for Red Hat Linux
#
# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and
# sysctl.conf(5) for more details.
 
# Controls IP packet forwarding
net.ipv4.ip_forward = 0
 
# Controls source route verification
net.ipv4.conf.default.rp_filter = 1
 
# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0
 
# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0
 
# Controls whether core dumps will append the PID to the core filename.
# Useful for debugging multi-threaded applications.
kernel.core_uses_pid = 1
 
# Extra parameters For 11g RAC installation
 
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.shmall = 2097152
kernel.sem = 250 32000 100 128
fs.file-max = 6553600
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default = 4194304
net.core.wmem_default = 262144
net.core.wmem_max= 262144
net.core.rmem_max = 4194304
 
[root@node2-pub ~]# 

After adding these lines to /etc/sysctl.conf, please run the below command as root to make them enabled.

[root@node2-pub ~]# mkdir -p /u01/app/crs
[root@node2-pub ~]# mkdir -p /u01/app/asm
[root@node2-pub ~]# mkdir -p /u01/app/oracle
[root@node2-pub ~]# mkdir -p /u02/ocfs2
[root@node2-pub root]# chown -R oracle:oinstall /u01
[root@node2-pub root]# chown -R oracle:oinstall /u02
[root@node2-pub root]# chmod -R 775 /u01/app/oracle
[root@node2-pub root]# chmod -R 775 /u01