You may need to cut down or split a file into smaller pieces sometimes. This is very useful when you want to cut down a large iso to fit into a DVD or CD. or can also be used to transfer over a network. To split the file into smaller pieces, we can use the […]
Archives for October 2017
CentOS / RHEL 6 : How to disable Transparent Huge pages (THP)
Transparent Huge Pages (THP) are enabled by default in RHEL 6 for all applications. The kernel will always attempt to satisfy a memory allocation using hugepages. If no hugepages are available (due to non availability of physically continuous memory for example) the kernel will fall back to the regular 4KB pages. Explicit Huge Pages V/s […]
CentOS / RHEL 7 : How to disable Transparent Huge pages (THP)
Explicit Huge Pages V/s Transparent Huge Pages There can be two types of HugePages in the system: Explicit Huge Pages which are allocated explicitly by vm.nr_hugepages sysctl parameter and Transparent Huge Pages which are allocated automatically by the kernel. Verify if THP is enabled “tuned.service” on CentOS / RHEL 7 set the transparent_hugepage to always […]
RHEL/CentOS 6,7 : How to caculate the size of hugepage used by a specific process/application
You have a system configured with hugepages and you want to find per-process hugepages utilization. # grep -i huge /proc/meminfo HugePages_Total: 2176 HugePages_Free: 2065 HugePages_Rsvd: 2065 Hugepagesize: 2048 kB Method 1 The following command can be used to see which processes are using THP: for i in /proc/*/smaps; do if [[ $(grep ‘^AnonHugePages’ $i | […]
CentOS / RHEL 6,7 : How to configure hugepages
What is hugepages HugePages is a feature integrated into the Linux kernel with release 2.6. This feature basically provides the alternative to the 4K page size (16K for IA64) providing bigger pages. HugePages is a method to have larger pages where it is useful for working with very large memory. Configure hugepages by using the […]
Linux OS Service ‘cpuspeed’
Service Name cpuspeed Description This executes a daemon which dynamically adjusts CPU speed and voltage based on demand for CPU and automatically detects available CPU speeds. This is necessary only for Note/Desktop PC, but not for server. This daemon monitors the system’s idle percentage and reduces or raises the CPUs’ clock speeds and voltages accordingly […]
How to disable auto completion (tab completion) in bash shell
Disabling auto-complete feature globally for all the users With bash shell you would usually have the auto completion feature turned on by default. To disable the auto complete feature of the Bash shell for all the users of the system, you can add the following parameter in the file /etc/inputrc: # vi /etc/inputrc set disable-completion […]
VCS (Infoscale Availability) : How to online and offline resources
Resource online basics Resources are brought online automatically when the service group is brought online. They can also be brought online manually after the maintenance task according to the order defined in the dependency tree. The resource agent runs the online entry point which in turn runs the specific startup operations required to bring the […]
VCS (Infoscale Availability) – Difference Between Frozen and TFrozen attributes
These service group attributes are used to indicate that the service group is frozen due to an administrative command. When a service group is frozen, all agent online and offline actions are disabled. Difference between Frozen or TFrozen attributes – If the service group is temporarily frozen using the hagrp –freeze group command, the TFrozen […]
VCS (Infoscale Availability) : How to freeze a Service Group
Why freeze the service group When you freeze the service group in VCS, it will continue to monitor the resources in the cluster. But does not allow service group or the resources to be brought online or offline. Failover is also disabled during the freeze period of the service group. The use case for the […]