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 split command. The syntax for the split command is : # split -b [size of split pieces] [file to split] [split file prefix] For example to split an iso file image.iso of size 4.6GB into smaller chunks of 2000MB use the below command: # … [Read more...] about How to split iso or file using ‘split’ command in Linux
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 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 … [Read more...] about CentOS / RHEL 6 : How to disable Transparent Huge pages (THP)
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 by default. Even if its disabled in grub kernel command line, the tuned service will set it to 'always' during boot. Below command … [Read more...] about CentOS / RHEL 7 : How to disable Transparent Huge pages (THP)
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' $i | grep -v '0 kB$') ]]; then echo -ne "$i procees maybe running THP mode if you are using THP mode in … [Read more...] about RHEL/CentOS 6,7 : How to caculate the size of hugepage used by a specific process/application
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 kernel tunable vm.nr_hugepages 1. Edit /etc/sysctl.conf file and specify the number of hugepages in the nr_hugepages parameter. The entry makes the parameter persist … [Read more...] about CentOS / RHEL 6,7 : How to configure hugepages
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 to minimize power consumption when idle and maximize performance when needed. It may also optionally be configured to reduce … [Read more...] about Linux OS Service ‘cpuspeed’
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 on This disable the auto complete feature of bash shell for all the users on the system. After saving the file, users will have to logout and login again … [Read more...] about How to disable auto completion (tab completion) in bash shell
Solaris : How to automate scp transfer (using passwordless ssh)
Because Secured Copy (SCP) is part of a suite of tools available with Secure Shell (SSH), you must first configure passwordless SSH before you can utilize the same for SCP. Authentication is checked against public key pairs for known hosts, instead of user id and password. Once you have SSH successfully configured to authenticate without a password, you can then utilize unprompted login with a secure copy. Configuring passwordless scp from host A to host B 1. Host A: Generate Key-pair using … [Read more...] about Solaris : How to automate scp transfer (using passwordless ssh)
How to configure passwordless ssh in Solaris
The post details out steps to configure passwordless ssh using RSA Public Key Authentication, in other words: passwordless login using public Key. This procedure is used to reduce the number of login prompts needed to do secure remote login with Sun Secure Shell (SSH) this including also SCP ( Secure Copy) and SFTP ( Secure File Transfer). Note: Its the same steps even for dsa keys , except the "ssh-keygen -t dsa" and stored files. ( /.ssh/id_dsa) Configuring passwordless ssh To … [Read more...] about How to configure passwordless ssh in Solaris
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 resource online. In normal day-to-day operations, you perform most management operations at the service group level. However, you may need to … [Read more...] about VCS (Infoscale Availability) : How to online and offline resources