lvm commands not found

-bash: pvscan: command not found
-bash: lvdisplay: command not found
-bash: vgcreate: command not found
-bash: lvcreate: command not found
-bash: lvscan: command not found
-bash: pvdisplay: command not found
-bash: lvm: command not found

If you are using CentOS or fedora or RHEL and you are getting these errors again and again when you try to run lvm commands. It means lvm is not installed or corrupted on your system. Reinstall lvm again.

yum install lvm2

If it is not able to find lvm2 package and shows

No package lvm2 available.

It means your repositories do not have this package.
Enable appropriate repository like base, remi, rpmforge or epel and install it again.

If you have enabled all available repositories and still it shows "No package available."
Check the file /etc/yum.conf
The lvm2 package should not be there in exclude packages.
Repos do not list exclude packages and do not install them. If it is under exclude attribute, remove it and run install command again.
It should be installed.