lvm (Linux Logical Volume Manager) command

lvm01

lvm layout

pvdisplay – shows you the current state of your physical volumes.

vgdisplay – shows you all volume groups

lvdisplay – shows you all logical volumes

lvscan – shows you all active volumes (disks)

lvs – is like lvscan but shows you less detail.

pvscan – scans all disks for physical volumes and shows disk space.

How to install rsync in Linux/Unix

rsync is a program that behaves in much the same way that rcp does, but has many more options and uses the rsync remote-update protocol to greatly speed up file transfers when the destination file already exists.

The rsync remote-update protocol allows rsync to transfer just the differences between two sets of files across the network link, using an efficient checksum-search algorithm described in the technical report that accompanies this package.

Debian or Ubuntu Linux

apt-get install rsync

or

sudo apt-get install rsync

Red Hat Enterprise Linux (RHEL)

up2date rsync

CentOS/Fedora Core Linux

yum install rsync

How to drop clean caches (Linux)

Command to drop cache

To free pagecache:

echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:

echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:

echo 3 > /proc/sys/vm/drop_caches

Strongly advise to run sync first before do that. You can use command as below

sync;echo 3 > /proc/sys/vm/drop_caches