Thursday, 14 August 2014
Kump Introduction
Kdump is the Linux kernel crash-dump mechanism. Oracle recommends that you enable the Kdump feature. In the event of a system crash, Kdump creates a memory image (vmcore) that can help in determining the cause of the crash. Enabling Kdump requires you to reserve a portion of system memory for exclusive use by Kdump. This memory is unavailable for other uses.
Kdump uses kexec to boot into a second kernel whenever the system crashes. kexec is a fast-boot mechanism which allows a Linux kernel to boot from inside the context of a kernel that is already running without passing through the bootloader stage.
When the kdump crash dumping mechanism is enabled, the system is booted from the context of another kernel. This second kernel reserves a small amount of memory and its only purpose is to capture the core dump image in case the system crashes.
Configuring the kdump Service:
There are three common means of configuring the kdump service: at the first boot, using the Kernel Dump Configuration graphical utility, and doing so manually on the command line.
Configuring the kdump at First Boot: The menu which we see during OS Installation.
Using the Kernel Dump Configuration Utility:
Select System → Administration → Kernel crash dumps from the panel, or type system-config-kdump at a shell prompt
Configuring kdump on the Command Line:
To configure the amount of memory to be reserved for the kdump kernel, edit the /boot/grub/grub.conf file and add crash kernel=M or crash kernel=auto
Kdump uses kexec to boot into a second kernel whenever the system crashes. kexec is a fast-boot mechanism which allows a Linux kernel to boot from inside the context of a kernel that is already running without passing through the bootloader stage.
When the kdump crash dumping mechanism is enabled, the system is booted from the context of another kernel. This second kernel reserves a small amount of memory and its only purpose is to capture the core dump image in case the system crashes.
Configuring the kdump Service:
There are three common means of configuring the kdump service: at the first boot, using the Kernel Dump Configuration graphical utility, and doing so manually on the command line.
Configuring the kdump at First Boot: The menu which we see during OS Installation.
Using the Kernel Dump Configuration Utility:
Select System → Administration → Kernel crash dumps from the panel, or type system-config-kdump at a shell prompt
Configuring kdump on the Command Line:
To configure the amount of memory to be reserved for the kdump kernel, edit the /boot/grub/grub.conf file and add crash kernel=M or crash kernel=auto
How to go previous date from current date
[root@node1 ~]# date
Sun Jul 13 05:29:50 EDT 2014
[root@node1 ~]# date -d "30 Days Ago"
Fri Jun 13 05:33:45 EDT 2014
Sun Jul 13 05:29:50 EDT 2014
[root@node1 ~]# date -d "30 Days Ago"
Fri Jun 13 05:33:45 EDT 2014
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