Linux system monitoring and statistics gathering

We will look at some Linux commands which will help us monitor system performance, gather statistics and view historical resource usage. Monitoring connections with ss command ss should be preinstalled for most modern Linux distributions Show established TCP connection ss -t Show established UDP connections ss -u Show ports listening for TCP connections ss -ltn…

Backup FreeNAS ZFS Dataset to Ubuntu running ZFS

We are setting up replication of snapshots for backup purposes on FreeNAS. We setup Ubuntu server and install ZFS on it. We will use this system to receive snapshot for backup purposes. We manually generated ssh key on FreeNAS. This was done by connecting to CLI and running commands below. ssh-keygen -q -t rsa scp…

Manage Time service on RH and CentOS 7

When Linux system first boots the hardware clock is read first. The time on the hardware clock read from local hardware clock in UTC – Universal Time. Local time is the actual time in the current time zone. System time, unlike Hardware clock maintained by operating system. System clock is completely independent of the hardware…

Expand KVM based image with lvm partition

Lets take a quick look at how to expand kvm raw image with lvm partition running CentOS7 guest. We will need to download gparted for this to re-size image. It cam be downloaded from here. We will be expanding our image by 10G.

Manually migrate LVM based vm from one KVM hosts to another

We have a KVM based VM on LVM volume that we need to migrate to different host. This is not hot-live migration and will be done offline. Lets looks at steps required to get it done. There may be many different ways to do it and this is just one of them.

How to find php script that sends mail from your linux system

We run into a problem where customers Linux vm was sending a lot of unwanted messages. In order to troubleshoot this problem we did 2 things. Instructions below are for CentOS 6 and 7 but will also work on other distributions with minor configuration changes. Option 1

Create and Mount LVM Volume

In this article we will look into creating LVM volume on remaining not partitioned space and formatting logical volume with ext4 file system . We also will look into mounting it via fstab. In our LAB we will use CentOS7 vm to demonstrate our steps.

Absolute and Relative Pathnames

Path or location in current directory tree is ether refereed to as Absolute or Relative. Lets take a look at what they are. Absolute Path: Absolute path also known as full or fully qualified path points to a file or directory in relation to / . When we execute pwd command we get absolute path.