Month: April 2021

How to reset the root password on redhat 8

So you end up here because you have lost your root password. On Red Hat Enterprise Linux 8, it is possible to have the scripts that run from the initramfs pause at certain points, provide a root shell, and then continue when that shell exits. This is mostly meant for debugging, but you can also use this method to reset a lost root password. To access that root shell, follow these steps:

  • Reboot your server.
  • Interrupt the boot loader countdown by pressing any key, except Enter.
  • Move the cursor to the kernel entry to boot.
  • Press e to edit the selected entry.
  • Move the cursor to the kernel command line (the line that starts with linux).
  • Append rd.break. With that option, the system breaks just before the system hands control from the initramfs to the actual system.
  • Press Ctrl+x to boot with the changes.
  • To reset the root password from this point, use the following procedure:
  • Remount /sysroot as read/write.

switch_root:/# mount -o remount,rw /sysroot

  • Switch into a chroot jail, where /sysroot is treated as the root of the file-system tree.

switch_root:/# chroot /sysroot

  • Set a new root password.

sh-4.4# passwd root

  • Ensure that all unlabeled files, including /etc/shadow at this point, get relabeled during boot.

sh-4.4# touch /.autorelabel

  • Type exit twice. The first command exits the chroot jail, and the second command exits the initramfs debug shell.
  • At this point, the system continues booting, performs a full SELinux relabel, and then reboots again.
If you are looking to learn Linux or host your website, you can buy VPS Hosting.

What is VPS Hosting?

A VPS is a complete server with its own operating system and virtual hardware built on top of physical server hardware. A Linux or Windows-based operating system known as a hypervisor is used to build virtual servers, datastores, virtual switches, virtual routers, virtual CPUs, and RAM. Some leading hypervisors are VMware, Citrix Xenserver, and KVM. With rapid provisioning of a VPS, you can scale horizontally to handle bursts in computing resources.

An important advantage of a VPS is that you can replicate and clone a VPS easily and within a short time. You can increase resources like CPU, RAM, and storage instantly by asking your VPS hosting provider. With SeiMaxim virtualization technology, you can scale your VPS up to 24TB RAM and 768 vCPUs, leaving our competitors far behind in this field. You can meet the demands of high-performance applications and memory-intensive databases, including SAP HANA and Epic Cache Operational database.

A greater advantage of using hypervisor is in the field of graphics visualization, rendering, and streaming. SeiMaxim VPS offers 3-D professional graphics that included GPU Pass-through and hardware-based GPU sharing with NVIDIA vGPU™, AMD MxGPU™, and Intel GVT-g™. A pass-through GPU is not abstracted at all but remains one physical device. Each hosted VPS gets its own dedicated GPU, eliminating the software abstraction and the performance penalty that goes with it. This GPU Pass-Through feature is ideally intended for graphics power users, such as CAD designers and Molecular modelers.

To cut the cost of a single VPS with a dedicated GPU, a shared GPU can be implemented.  Shared GPU allows one physical GPU to be used by multiple VPS at the same time. Because a portion of a physical GPU is used, performance is greater than emulated graphics, and there is no need for one card per VPS. This feature enables resource optimization and increases the performance of the VPS. The graphics workload of each VPS is passed directly to the GPU without processing by the hypervisor.

How To Monitor VMware envirnment with Grafana

This step-by-step guide uses the Official telegraph vSphere plugin to pull metrics from vCenter. We will pull metrics such as compute, network and storage resources. Before starting with this guide, I assume you have a freshly installed operating system, ubuntu 20. so let’s being with our work.

Step: 1 Install Grafana on Ubuntu

This tutorial tested on freshly installed OS Ubuntu 20.04.

  • Start your Grafana installation.


sudo dpkg -i grafana_7.1.3_amd64.deb

  • Now start and enable your Grafana service.

sudo systemctl start grafana-server.service

sudo systemctl enable grafana-server.service

  • Check Grafana service status.

sudo systemctl status grafana-server.service

  • At this point, Grafana is installed, and you can log in to your Grafana by following

url: http://[your Grafana server ip]:3000

The default username/password is admin/admin

  • Upon the first login, Grafana will ask you to change the password.
  • Be careful HTTP is not a secure protocol. You can further secure it by putting SSL certificates.

Step: 3 Install Influx DB

  • Inquire about the available InfluxDB version in your apt-cache by the following command.

sudo apt-cache policy influxdb

It will be the last stable version of InfluxDB. We will use a later version 1.8 of InfluxDB, so we will update the apt cache first and add the required information to the repository.

wget -qO- | sudo apt-key add -

source /etc/lsb-release

echo "deb${DISTRIB_ID,,} ${DISTRIB_CODENAME} stable" | sudo tee /etc/apt/sources.list.d/influxdb.list

sudo apt update

sudo apt-cache policy influxdb

sudo apt update

sudo apt-cache policy influxdb

sudo apt install influxdb -y

  • Check the status and ensure that it sustains over the reboot.

sudo systemctl start influxdb

sudo systemctl status influxdb

sudo systemctl enable influxdb

  • The InfluxDB will listen on port 8086, and if your server is on the internet, then depending on any existing firewall rules, anybody may be able to query the server using the URL

https://[your domain name or ip]:8086/metrics

  • On my local machine where I am doing this test, is not having any firewall enabled, but if you have allowed or using public IPs, you can prevent direct access by doing these commands

iptables -A INPUT -p tcp -s localhost --dport 8086 -j ACCEPT

iptables -A INPUT -p tcp --dport 8086 -j DROP

Step: 4 Install Telegraf

  • Now we are going to install telegraf.

sudo apt install telegraf -y

  • Start Telegraf and ensure it starts in case of reboot.

sudo systemctl start telegraf

sudo systemctl status telegraf

sudo systemctl enable telegraf

  • Configure Telegraf to pull Monitoring metrics from vCenter, so here we will configure Telegraf main configuration file:
  • In this /etc/telegraf/telegraf first, you need to add information for influxdb.
  • change your influxdb credentials.


urls = ["http://<Address_of_influxdb_server>:8086"]
database = "vmware"
timeout = "0s"

#only with if you are using authentication for DB

#username = "USERNAME_OF_DB"

#password = "PASSWD_OF_DB"


# Read metrics from VMware vCenter
## List of vCenter URLs to be monitored. These three lines must be uncommented
## and edited for the plugin to work.
vcenters = [ "https://<vCenter_IP>/sdk" ]
username = "administrator@vsphere.local"
password = "PASSWD"
## VMs
## Typical VM metrics (if omitted or empty, all metrics are collected)
vm_metric_include = [
# vm_metric_exclude = [] ## Nothing is excluded by default
# vm_instances = true ## true by default
## Hosts
## Typical host metrics (if omitted or empty, all metrics are collected)
host_metric_include = [
# host_metric_exclude = [] ## Nothing excluded by default
# host_instances = true ## true by default
## Clusters
cluster_metric_include = [] ## if omitted or empty, all metrics are collected
# cluster_metric_exclude = [] ## Nothing excluded by default
# cluster_instances = false ## false by default
## Datastores
datastore_metric_include = [] ## if omitted or empty, all metrics are collected
# datastore_metric_exclude = [] ## Nothing excluded by default
# datastore_instances = false ## false by default for Datastores only
## Datacenters
datacenter_metric_include = [] ## if omitted or empty, all metrics are collected
# datacenter_metric_exclude = [ "*" ] ## Datacenters are not collected by default.
# datacenter_instances = false ## false by default for Datastores only
## Plugin Settings
## separator character to use for measurement and field names (default: "_")
# separator = "_"
## number of objects to retreive per query for realtime resources (vms and hosts)
## set to 64 for vCenter 5.5 and 6.0 (default: 256)
# max_query_objects = 256
## number of metrics to retreive per query for non-realtime resources (clusters and datastores)
## set to 64 for vCenter 5.5 and 6.0 (default: 256)
# max_query_metrics = 256
## number of go routines to use for collection and discovery of objects and metrics
# collect_concurrency = 1
# discover_concurrency = 1
## whether or not to force discovery of new objects on initial gather call before collecting metrics
## when true for large environments, this may cause errors for time elapsed while collecting metrics
## when false (default), the first collection cycle may result in no or limited metrics while objects are discovered
# force_discover_on_init = false
## the interval before (re)discovering objects subject to metrics collection (default: 300s)
# object_discovery_interval = "300s"
## timeout applies to any of the api request made to vcenter
# timeout = "60s"
## Optional SSL Config
# ssl_ca = "/path/to/cafile"
# ssl_cert = "/path/to/certfile"
# ssl_key = "/path/to/keyfile"
## Use SSL but skip chain & host verification
insecure_skip_verify = true


  • You only need to change the credential of vcenter and influxdb
  • Start and enable telegraf service after making the changes.
  • sudo systemctl restart telegraf
  • sudo systemctl enable telegraf

Step: 4.1 Check InfluxDB Metrics

  • We need to confirm that our metrics are being pushed to InfluxDB and that we can see them.
  • If you are using authentication then open  InfluxDB shell like this:

$ influx -username 'username' -password 'PASSWD'

  • We need to confirm that our metrics pushed to InfluxDB and that we can see them.
    If you are using authentication, then open the InfluxDB shell by this:

$ influx

  • Then:

> USE vmware

  • Using database vmware:
  • Check if there is an inflow of time series metrics.


name: measurements






























Step 5: Add InfluxDB Data Source to Grafana

  • Login to Grafana and add InfluxDB data source
  • Click on the configuration icon and then click datasource.
  • Click Add influxDB data source.
  • Insert all the relevant information under HTTP and influxDB details shown into the red boxes below:
  • If you used a password in your influxDB you might put it here.


Step 6: Import Grafana Dashboards

  • The last action is to create or import Grafana dashboards:
  • Building a Grafana dashboard is a lengthy process, so we are using a community dashboard built by Jorge de la Cruz.


  • We will import this pre-build Grafana dashboard #8159. The moment you did import, you will see your Grafana dashboard.


RSYNC: File size in destination is larger than source

You may notice that after running rsync your file size in destination becomes larger than the source. This is most likely due to sparse files. To allow rsync to manage sparser files more efficiently so they took less space use the -S flag.

rsync -S sparse-file /home/sparser-file

After rsync is done, check the destination file with the du command and the filesize will be almost the same as the source file.