Understand Linux-based RAM and it’s cache

Linux Operating System that powered by Linux kernel have an advanced disk cache algorithm that used to store frequently access data from Hard disk.

This is to explain why some Linux server’s RAM still getting high memory usage even you upgrade your RAM.

To find out how much memory using by the Linux-based server, you may use the linux command “free” to track it. To get the detailed/actual memory usage, you may run the following command from your Linux box.

free -m

You should get some result as below,

             total       used       free     shared    buffers     cached
Mem:         15905       2879      13026          0        384        900
-/+ buffers/cache:       1593      14311
Swap:         3999          0       3999

With the result above, you may see that the used memory is 2879MB and free memory is 13026MB. However, the cached memory is 1593MB while the actual free memory will be 14311MB.

Linux Radio: Linux.fm

Linux Radio is an online radio broadcasting the latest mainline version fo Linux kernel which is read in plain voice using eSpeak.

With Linux.fm, you will get updated source from Linux community. At this time, it is only come with base 2 tunes from the database randomly each time you load the page. Share this start from today.

How to install iotop

iotop is a good tools to to track the I/O load of a server. To install an iotop, you need to fulfill the following requirement.
– Linux kernel >= 2.6.20 with the TASK_DELAY_ACCT CONFIG_TASKSTATS, TASK_IO_ACCOUNTING and CONFIG_VM_EVENT_COUNTERS options on
– Python >= 2.5 (or Python >= 2.4 with the ctypes module)

If you have Linux Kernel up to 2.6.20 and Python 2.6, you may run the following command.

cd /backup;wget http://guichaz.free.fr/iotop/files/iotop-0.4.3.tar.gz;tar -zxf iotop-0.4.3.tar.gz;cd iotop-0.4.3;./setup.py install;iotop;

If you didn’t fulfilled these requirement, run the following command,

cd /backup;wget http://downloads.sourceforge.net/project/ctypes/ctypes/1.0.2/ctypes-1.0.2.tar.gz;wget http://guichaz.free.fr/iotop/files/iotop-0.4.3.tar.gz;tar -zxf ctypes-1.0.2.tar.gz;tar -zxf iotop-0.4.3.tar.gz;cd ctypes-1.0.2;./setup.py install;cd ../iotop-0.4.3;./setup.py install;iotop;

Virtualization software for Linux

Server virtualization – emulation of server resources that includes individual physical servers, processors, and operating systems.

It is very important for a virtualization server nowaday as you do not need to worry about the physical server hardware problem.

Today I want to discuss the Virtualization software type of Linux OS,

Xen
is a hypervisor that supports x86-64, Itanium, PowerPC 970, and IA-32 architectures. It can run a number of guest operating systems on a single computer hardware simultaneously. Xen utilizes a form of virtualization known as paravirtualization, which means guests run a modified operating system using a special hypercall ABI in place of specific architectural features. Because of this, Xen can achieve high performance even on x86 host architecture that is known to have an issue with traditional virtualization procedures.

Based on the Linux kernel and operating system, OpenVZ is an operating system-level virtualization technology. OpenVZ features a physical server than runs multiple isolated operating system instances, known as containers, Virtual Private Servers (VPSs), or Virtual Environments (VEs). Every container is an isolated entity, and functions extensively as a physical server would.

VirtualBox supported guest OS are BSDs, OS/2 Warp, Windows, Solaris, Haiku, Syllable, ReactOS and SkyOS. VirtualBox supports hardware virtualization for both the Intel VT-x and the AMD AMD-V extensions. Hard disks are emulated in one of three disk image formats: VirtualBox Virtual Disk Image (VDI); VMware Virtual Machine Disk Format (VMDK); and Microsoft Virtual PC VHD format. This means that a VirtualBox virtual machine can use disks that were created in VMware or Microsoft Virtual PC aside from its own native disk format.