Package require to analyze kernel core dump in RHEL system

To analyze the system crash dump file (vmcore) , we must have crash and debuginfo package installed on system. 

To install the crash package in your system, run the following as root:

#yum install crash

To install the kernel-debuginfo package, make sure that you have the yum-utils package installed and run the following command as root:

#debuginfo-install kernel

If not able to download the debuginfo kernel package with above command, then download the package from ftp server: http://ftp.heanet.ie/mirrors/puias/updates/


For example to download the RHEL6 (32-bit) related debuginfo package from:
http://ftp.heanet.ie/mirrors/puias/updates/6Server/en/os/debug/i386/

For example to download the RHEL6 (64-bit) related debuginfo package from:
http://ftp.heanet.ie/mirrors/puias/updates/6Server/en/os/debug/x86_64/


Package need to download:
1) Determine the kernel version of generated "vmcore" system , by executing "uname -r" command
2) Download the kernel-debuginfo-`uname -r`.rpm and kernel-debuginfo-common-`uname -r`.rpm
3) Install the package through rpm command i.e "rpm -ivh <package name>

Printk Timestamp Enable Method

We can enable and disable printk timestamps at runtime, by writing to /sys/module/printk/parameters/time.

By default printk timestamp is disable : 

[root@localhost ~]# cat /sys/module/printk/parameters/time

N

In order to enable the printk timestamp execute the below command:

[root@localhost ~]# echo "1" > /sys/module/printk/parameters/time

[root@localhost ~]# cat /sys/module/printk/parameters/time

Y

[root@localhost ~]# dmesg

[11320.847977] Hello World..

After that will able to see the timestamp. 

In order to disable to printk timestamp execute the below command

[root@localhost ~]# echo "0" > /sys/module/printk/parameters/time

[root@localhost ~]# cat /sys/module/printk/parameters/time

N

Fix locale issue in RedHat distro

Getting Error while logging into the RHEL system:

-bash: warning: setlocale: LC_CTYPE: cannot change locale (UTF-8): No such file or directory

OR

Getting Errot while executing locale command :

$ locale

The output is...

locale: Cannot set LC_ALL to default locale: No such file or directory LANGLANG=en_US.UTF-8

LC_CTYPE="en_US.UTF-8"

LC_NUMERIC="en_US.UTF-8"

...

Solution for this issue:

Add the following line in "/etc/environment" file . 

LC_ALL=en_US.UTF-8

LC_CTYPE=en_US.UTF-8

To see the result, logout and login to shell again

Linux Kernel Compilation on Same system

In Linux , kernel is core of Operating System. Time to time updating the kernel of Operating System will give latest security , fixes of  bugs and advance features.

Steps to compile and install the latest kernel in Linux Desktop:

Step#1:  Download the latest stable kernel code from https://www.kernel.org/:

Step#2:  Untar the kernel source code:

             #tar -xvf  linux-3.15.5.tar.xz

Step#3:  Configure the kernel according to system :

             #cd linux-3.15.5

             #make menuconfig

• make menuconfig commands directly configured the kernel according to the your system.
• Depend upon requirement user can select the functionality they required in menuconfig GUI.
• Other option to configure the kernel configuration is that edit the .config (hidden) file.

Step#4:  Compile the main kernel:

             #make -j8

• Option j is used to compile the kernel on multi-thread core, it utilize mutlithread compilation  feature of  kernel.

Step#5:  Compile the kernel modules:

             #make modules

Step#6:  Install the kernel modules:

            #make modules_install

• After installation of kernel module, in system /lib/modules/3.15.5/ gets created

Step#7: Install the kernel:
           #make install

• The make install command will install the kernel in /boot directory.
• Following files gets install in /boot directory
• vmlinuz-3.15.5 -> Kernel binary code
• System.map-3.15.5 -> Exported symbols
• initrd.img-3.15.5 -> Temporary root file system used in bootup process
• config-3.15.5 -> Compiled kernel configuration
• make install command , update the grub with installed kernel details in /boot/grub/grub.conf file

Step#8: Reboot 

           #reboot

Step#9: Verify the kernel version

          #uname -r 

            3.15.5

• During boot-up process, select the required kernel(other than latest install) in grub. 
• By default grub have latest kernel i.e 3.15.5 as default and system boot with that