Monthly Archives: August 2017

How to release the Elastic IP in AWS

Learn how to disassociate elastic IP from EC2 and how to release elastic IP in AWS with screenshots. Also, understand how elastic IP is billed and the cost of billing.

In our previous article we understood how to allocate elastic IP to your AWS account & how to associate that elastic IP to EC2 instance. In this article we will walk through steps to disassociate elastic IP from EC2 instance and then release elastic IP from your AWS account.

Before we run into steps lets look at elastic IP billing information which will help you to judge why it is important to release un-used elastic IP back to AWS.

Elastic IP billing

At the most you can allocate 5 elastic IP for an AWS account per region. If you have a requirement of more, you need to reach out to the AWS team to raise this limit through form. This limit is set by Amazon since IPv4 is a scarce resource.

Coming to the billing part, you will be billed for each elastic IP which is not being used anywhere but allocated to your AWS account. This is to impose efficient use of such scarce resources. You will not be billed for elastic IP if below conditions are met –

Elastic IP allocated to you is associated with EC2 instance
That EC2 instance has only one elastic IP associated
That EC2 instance is in running state.

How to remove elastic IP from EC2 instance

In AWS terms, its process to disassociate elastic IP from EC2 instance. The process is pretty simple. Login to EC2 console and navigate to Elastic IPs. You will be listed with all available Elastic IPs in your account. Choose one to disassociate and choose disassociate from the action menu. You will be shown a pop up like one below :

Confirm disassociation by clicking the disassociate address button. Your elastic IP will be removed from an EC2 instance and the instance will be assigned with public IP from AWS automatically. You can confirm empty elastic IP from EC2 instance details.

Now you have successfully disassociated elastic IP from EC2 instance. But it is still allocated to your AWS account and you are getting billed since you are not using it anywhere. You need to release it back to the AWS pool if you are not planned to use it for any other purpose so that you won’t be billed for it.

How to release elastic IP from AWS account

Releasing elastic IP means freeing it from your account and making it available back in the AWS pool for someone else to use it. To release login to EC2 console and navigate to Elastic IPs page. From the presented list select elastic IP you want to release and choose release address from the actions menu. You will be prompted with pop up like below :

Confirm your action by hitting the release button. Your elastic IP will be released back to the AWS pool and you won’t be able to see it in your account anymore!

How to assign Elastic IP to EC2 Linux instance

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Learn how to assign elastic IP to the ec2 Linux instance in AWS. Step by step procedure explaining how to allocate elastic IP to your account and how to associate it to EC2.

Associate Elastic IP to EC2 instance tutorial

In this article we will walk through steps to assign elastic IP on Linux EC2 instance. First of all you might think what is elastic IP and why to use it? We have already covered here elastic IP basics and the difference between elastic and public IP. Without further delay lets move onto our tutorial of assigning elastic IP to EC2 instance.

Get ready your EC2 for Elastic IP

First of all you should have launched your EC2 instance. It should be in a running state. Once running you can check instance properties in EC2 console under AWS dashboard and its IP details should be as below :

Here you can see the Elastic IP field is empty and the Public IP field is populated with AWS auto-assigned IP address.

Remember, only one of these two exist for EC2 instance; either public or elastic IP.

Allocate Elastic IP to AWS account

The second step is to allocate your AWS account new Elastic IP if you haven’t allocated any elastic IP before.

Note that only 5 elastic IP can be allocated to a single AWS account and you will be charged for any elastic IP which is not being used.

Let’s see how to allocate an elastic IP to the AWS account. Navigate to VPC under your AWS dashboard. You will be presented with the VPC console where on the left pane you can find the ‘Elastic IPs‘ menu. Click on that to open the Elastic IP dashboard. Here you see the ‘Allocate New Address‘ button. On the next screen click ‘Allocate‘ and you will be allocated with new Elastic IP in your account. I created GIF (below) of the whole process for your reference.

Associate Elastic IP to EC2 instance

Now you have one elastic IP allocated to your account. You need to associate this IP to EC2 instance. Again head back to Elastic IP dashboard where you will see your newly allocated elastic IP. Select it and choose ‘associate address‘ from the action menu. You will see pop up like below :

Select the resource type as an instance. Select your EC2 Instance from the dropdown. Private IP{ is elastic IP which you are associating now (pre-populated).

Here you can see a warning if you associate elastic IP with instance your public IP will be released. This is what we mentioned in the first part of this tutorial that only one IP can exist.

Once associated you can check IP details as below :

where you can confirm that it is associated with EC2 instance by verifying ‘Instance‘ field value.

Verify Elastic IP on EC2 instance

You are done! You already associated your elastic IP to EC2 instance. Now you can verify it with all the below methods :

Connect using elastic IP via putty. You should be connected (provided security groups are configured properly)
Go to the EC2 console and check the instance details. You will see the Elastic IP field is populated and Public IP field reflects elastic IP as below :

Login to your EC2 instance and run below commands which gives elastic IP as output. Make sure you have curl, wget utilities installed. If not, install them using YUM or APT.

root@kerneltalks # curl checkip.amazonaws.com
13.126.158.173

root@kerneltalks # wget -qO- http://instance-data/latest/meta-data/public-ipv4
13.126.158.173

In our next article we have discussed how to dis-associate and release elastic IP also elastic IP billing.

Benefits of cloud computing over the traditional data center

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Article listing benefits of cloud over traditional datacenter. 7 different aspects of cloud vs on-premise datacenter.

In the past few years, the cloud industry is gaining good momentum. Many companies are moving their workloads to cloud from the traditional data centers. This trend is increasing day by day due to the list of advantages cloud offers over the traditional data centers. In this article we will walk through these advantages of cloud over traditional datacenter. This is also one of the basic cloud interview questions where they tell you to list of pros and cons of the cloud. Without much delay lets jump into cloud vs data center discussion.

Low maintenance cost. For a customer maintenance cost is almost nil. Since you are using hardware from the cloud provider’s datacenter, you don’t need to maintain hardware at all. Your cost is saved from geographical location cost, hardware purchase, upgrades, datacenter staff, power, facility management cost, etc. All this is bared by the cloud provider. Also, for cloud providers, this is also low since they are operating multiple clients from the same facility and hence cost is low compared to cost one has to bear when all those clients are operating from different datacenters. This is very much environment friendly too since you are reducing the need for multiple facilities to fewer ones.
Cheap resources. Cloud providers have a pool of resources and from which you get assigned your share. This means cloud providers maintain and operate a large volume of resources and distribute smaller chunks to customers. This obviously reduces the cost of maintenance and operation for cloud providers and in turn provides low cost, cheap resources to customers.
Scale as per your need. In a traditional data center you have to study and plan your capacity well in advance to finalize your hardware purchase. Once purchased you are stuck with purchased limited capacity and you can not accommodate if capacity requirement grows beyond limit before your estimated time. It again goes through planning, purchasing new hardware which is a time-consuming process. In the cloud you can scale up and scale down your computing capacity almost instantly (or way shorter in time than traditional purchase process). And don’t even need to worry and follow for approvals, purchase, billing, etc things.
Pay as you use. In traditional data centers whenever you buy hardware you make an investment upfront even if you don’t use the full capacity of purchased hardware. In the cloud, you are billed per your use. So your expenditure on computing is optimum with your use.
The latest technology at your service. Technology changing very fast these days. Hardware you buy today becomes obsolete in a couple of months. And if you are making huge investments in hardware, the company expects to use it at least for a couple of years. So you are stuck with the hardware you brought with a nice price tag and now way behind from its latest counterparts. Cloud provides you the latest tech always and you don’t need to worry about upgrades or maintenance. All these hardware aspects are the headache of cloud providers and they take care of it in the background. As a customer, all the latest technology is at your service without any hassle.
Redundancy. Redundancy in traditional datacenter means cost investment to build almost identical facilities of the primary. Along with it also involves cost for infrastructure which connects them. Also, on-site redundancy for power, network, etc. is also expensive and maintenance prone. When you are opting cloud, everything said previously is just vanished from your plate. Cloud at single entity level like single server, storage disk, etc is already redundant. Nothing to be done and no extra cost is being billed to you for it. For your infra design requirement if you want, you can use ready-made services provided by cloud (for redundancy) and you are all set from failures.
Accessibility. With an on-premise datacenter, you have very limited connectivity mostly locally. If you want access to inside entities, you need to maintain your own VPN. Cloud services have a portal with access to almost all of their services over the web. It can be accessed from anywhere with internet. Also, if you want to opt-in for a VPN, you get a pre-configured secure VPN from your cloud provider. No need for designing and maintaining a VPN!

Let us know your views on cloud vs on premise datacenters in comments section below.

Difference between elastic IP and public IP

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Learn what is elastic IP and public IP means in AWS. List out all differences between elastic IP and public IP in AWS.

I was having a conversation about AWS with one of my friends and he came up with the question what is the difference between elastic IP and public IP? So, I explained to him and thought why not draft a post about it! So in this article, we will see the difference between elastic IP and public IP in AWS. This can be a cloud interview question so without much delay lets get into elastic IP vs public IP battle.

What is elastic IP in AWS?

First thing first, let’s get basics clear. What is the elastic IP? It is IPv4 IP address designed and exists for dynamic cloud computing and reachable over the internet. By name, you can imagine it’s a flexible IP that can be used or mapped rapidly from one EC2 instance to another when a currently associated instance fails. This way end-user or application continues to talk to the same IP even if the instance behind it fails. They are like static public IPs allocated for your AWS account.

What is Public IP in AWS?

Public IP is IPv4 IP address which is reachable over the internet. Remember switching flexibility of Elastic IP is not available for this IP. Amazon also assigns external/Public DNS name (shown in the screenshot) to instances who receives public IP. The public IP of the instance is mapped to the primary private IP of that instance via NAT (Network Address Translation) by default.

Refer below screenshot from the EC2 console of AWS and observe where you can check your elastic IP, public IP, and public DNS name.

Check elastic IP, public IP and public DNS in EC2 AWS console

Difference between elastic IP and Public IP

Now let’s look at the difference between these two IP types.

Whenever a new EC2 instance spins up, it’s assigned with public IP by default. Elastic IP is not assigned by default.
Elastic IPs are assigned to AWS accounts which you can attach to instances. Public IPs assigned to instances directly.
When an instance is stopped and started again, public IP gets changed. But if the instance is assigned with elastic IP, it will remain the same even if the instance is stopped and started again.
If elastic IP is allocated to your account and not in use then you will be charged for it on an hourly basis.
Public IP released once your instance is stopped so no question of getting charged for not using it.
You won’t be able to re-use the same public IP since its allocated from the free IP pool. You can always re-use, re-attach elastic IP to other instances when it is released from the current instance.
You can not manually attach or detach public IP from the instance. It’s auto allocated from the pool. Elastic IP can be manually attached and detach from the instance.
You can have a maximum of 5 elastic IP to your account per region. But, you can have as many public IPs as EC2 instances you spin up.
You can have either of them for an instance. If you assign elastic IP to instance then its currently assigned public IP will be released to the free pool.

Datacenter presence of top Cloud providers

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An overview of the global data center presence of top Cloud companies like AWS, Google Cloud, Azure, etc. This article lists maps and links which will help you understand the data center presence of various firms.

All companies are moving to the cloud now. Since the cloud model aims at pay-per-use its best fit in cost-cutting for every company that works in the IT field. The latest hardware and technologies are at your service without investing and worrying about the maintenance of hardware and facilities is the biggest benefit luring customers to cloud companies.

Since the cloud is a hot cake and its demand is growing day by day, we see lots of players in the cloud providers market. It’s not easy to offer cloud services since you need huge facilities all over the globe rather a network of such facilities across the globe to build your own cloud. It’s not an easy task, not at all! Data centers are the backbone of these clouds. They house the hardware which actually runs cloud services. So it’s important to know your cloud provider’s data center locations which helps you deciding many aspects of your services before moving in.

Here in this article, we will be listing all top-level cloud provider’s data center locations. This information is available on their respective websites, but we are consolidating it here for your quick reference!

Below data is as on 24th May 2020

Amazon Web Service (AWS)

AWS global infrastructures consist of 24 regions with 76 availability zones within & 216 Point of Presence. Zone normally indicates one or more datacenter. The latest updated details can be found on their page here. AWS global infrastructure map looks like :

AWS Global Infrastructure. Image credit : Amazon

Where, numbers denote the number of availability zones in that region and green circles show upcoming regions.

AWS Infrastructure is visually represented on this website which is nice to understand.

Google Cloud Platform

Another biggie in the Cloud service market. Google has a presence in 23 regions with 70 zones within & 140 Network Edge Locations. Google also shared their network map details along with data center presence here on this page. Their global locations map looks like below :

Google Cloud global locations. Image credit : Google

Where number denotes available zones and blue ones are upcoming locations.

Microsoft Azure

Azure is a cloud service from Microsoft. Their global infrastructure consists of 60+ regions. The latest and updated info can be grabbed from this page. Microsoft’s data center map looks like one below :

Where triangle ones are upcoming locations.

IBM Bluemix

IBM offers its cloud platform as a service in Bluemix. The latest updated infra details can be found here on this page.

HP Cloud

I could not find infrastructure maps or consolidated information for the Hewlett Packard (HP) cloud global infrastructure. However I got some info on the HP UK website here. Where HP states they have 28 data centers powering their cloud and they are building new 5 data centers in the EMEA region.

vCloud

VMware cloud also referred to as vCloud has 11 zones in a total of 4 countries. VMware doesn’t define regions, rather they deny zones within countries. VMware released this PDF which has all these details.

So looking at above maps and numbers we can jot down current infrastructure reach of three top cloud companies in below table :

	*Amazon web services*	*Google Cloud*	*Microsoft Azure*
Regions	16	11	36
Zones	44	33
Upcoming regions	5	6	6

Every company uses different terminology. Where regions are common for all but not zones. Zones are referred to as single or multiple data centers in that geographical vicinity. Microsoft, IBM doesn’t refer zones term they only refer to regions. VMware doesn’t refer regions they only refer to country-wise zones. So the exact data center count for each company is not known rather shouldn’t be!

Let us know if you have more information of links regarding data center details of cloud providers (publically made available by owners) in comments below.

Double century! Celebrating 200 posts!

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Here we are on the 200th block! Kerneltalks journey of 10 months! Crawling web of Linux, Unix & scripts for the goodness of sysadmin!

And here we are on another milestone 200 posts! Six months ago we hit 100 posts milestone and now double century!

KernelTalks grew big and steadily past few months. Our pageviews increased which almost totaled to 160K as I am writing this article. Our social reach extended too in terms of fan page followers, likes, shares, comments on, or posts. We are also observing daily email subscribers signing up for our newsletters which indicates the reader’s interest in upcoming articles! All these numbers are available here.

In terms of traffic, we observe a significant rise in organic search traffic from search engines which is almost 15-20% of total traffic. SEO tuning, SSL implementation, and speed-boosting with CDN helped us to climb the search engine ladder. Alexa ranking is leaping day by day confirming increasing traffic to blog. Currently holding 380K rank globally. KernelTalks also featured in the top 60 Linux blog list by Feedspot.

KernelTalks gonna complete one year in a couple of months! Considering millions of blogs on the internet and budding new ones every other day, this progress is pretty good for the first year. Hope to see some more good numbers on our first anniversary! Till then have a happy read!

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    +------------------------------------+      ` )  /( ( /(     )         ( /(   (            (
    |                                    |       ( )(_)))\()) ( /(   (     )\())  )\ )   (    ))\
    |    +------> 200 posts! <------+    |      (_(_())((_)\  )(_))  )\ ) ((_)\  (()/(   )\  /((_)
    |                                    |      |_   _|| |(_)((_)_  _(_/( | |(_)  )(_)) ((_)(_))(
    |         www.kerneltalks.com        |        | |  | ' \ / _` || ' \))| / /  | || |/ _ \| || |
    |                                    |        |_|  |_||_|\__,_||_||_| |_\_\   \_, |\___/ \_,_|
    +------------------------------------+                                        |__/

XFS filesystem in Linux

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Learn about the XFS filesystem in Linux. An article explaining what is xfs, features, and commands of XFS. Also, how to migrate from EXT to the XFS file system.

What is xfs?

XFS is a high-performance file system designed by Silicon Graphics Inc in 1993. It is the default file system in RHEL7. XFS supports parallel IO operations because of its allocation group structure which makes it high performance operating file system. Journaling features helps it in faster data recovery in case of a crash. Lets quickly walk through a few aspects of XFS for your understanding.

Features of XFS

Its 64-bit file system with a max file system size of 8EB.
Supports metadata journaling which helps in faster data recovery in case of a system crash.
It can be extended while mounted and active.
It is internally partitioned into allocation groups. 4 different allocation groups available.
Directory quotas help to limit quota over the directory tree.
Quota journaling avoids quota consistency checks after the crash and hence quicker recovery
Extended attributes associated with each file. Those are additional name/value pairs.
Online de-fragmentation is supported.
It has native backup (xfsdump) & restore (xfsrestore) utilities.

How to upgrade EXT to XFS

The obvious question is how to upgrade from ext4 to xfs? or upgrade from ext3 to xfs etc. We have different ways to upgrade ext file systems but there is no full-proof way to upgrade ext to xfs. You can have below approach to migrate from ext to xfs filesystem –

Create a new xfs file system
Copy over data from old ext file system to xfs using copy or rsync
Remove old ext file system

Commands for XFS file system management

Create xfs file system : mkfs.xfs command.
Mount xfs file system : No extra switch for mount command
Quota management : xfs_quota command
Extending file system : xfs_growfs command
Repair file system : xfs_repair command
Suspend write on file system : xfs_freeze command (-f for suspend, -u for resume)
Bakcup : xfsdump command
Restore : xfsrestore command
Print file system information : xfs_info command
De-fragmentation : xfs_fsr command with no argument
Debug mode : xfs_db command

We covered few of these commands in detail in our next article.

Conclusion

XFS is a high-performance filesystem available in most Linux distro and as a default in some. We will see the difference between ext3, ext4, and xfs in upcoming articles along with the XFS command in detail.

Upgrade EXT filesystem in Linux (RHEL, CentOS, Ubuntu)

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Learn how to upgrade the ext filesystem in Linux like RHEL, Centos, Ubuntu, etc. Steps for upgrading ext2 to ext3, ext3 to ext4, and ext2 to ext4.

Upgrade filesystem from ext2 to ext3 to ext4

In our last article we saw the difference between ext2, ext3, and ext4 file systems in Linux. In this article we will walk through how to upgrade ext2 to ext3 or ext4 on RHEL, CentOS, or Ubuntu.

How to upgrade ext2 to ext3

To upgrade ext2 volume lets first format volume with ext2 filesystem.

# mke2fs /dev/vg01/lvol0
mke2fs 1.42.13 (17-May-2015)
Creating filesystem with 53248 1k blocks and 13328 inodes
Filesystem UUID: b3c39dcf-e00f-414c-8306-46d985674b6e
Superblock backups stored on blocks:
        8193, 24577, 40961

Allocating group tables: done
Writing inode tables: done
Writing superblocks and filesystem accounting information: done

Lets confirm file system type which we just formatted.

# df -T /mydata
Filesystem             Type 1K-blocks  Used Available Use% Mounted on
/dev/mapper/vg01-lvol0 ext2     51559   842     48055   2% /mydata

You can see its ext2 type in above output under second column.

Now to upgrade it to ext3 you need to unmount it, so there is downtime involved. After un-mount use tune2fs command to upgrade and mount it.

# umount /mydata

# tune2fs -j /dev/vg01/lvol0
tune2fs 1.42.13 (17-May-2015)
Creating journal inode: done

# mount /dev/vg01/lvol0 /mydata

#  df -T /mydata
Filesystem             Type 1K-blocks  Used Available Use% Mounted on
/dev/mapper/vg01-lvol0 ext3     47463   859     43942   2% /mydata

Observe above outputs carefully. We did –

Un-mount filesystem
Run tune2fs command with -j switch
Mount file system

ext2 has been upgraded to ext3 which can be confirmed in last output.

Make sure you make changes in /etc/fstab to reflect proper file system type for your related mount point.

How to upgrade ext3 to ext4

To upgrade to ext4 filesystem you need to enable file system features on the file system with tune2fs command. Those are – dir_index (Speed up directory lookups), extents (Stores locations in inodes), uninit_bg (reduce e2fsck time).

After successful setting features of file system you need to run e2fsck to fix file system data structures on disk for new modified features. To run e2fsck you have to unmount the file system.

# tune2fs -O extents,uninit_bg,dir_index /dev/vg01/lvol0
tune2fs 1.42.13 (17-May-2015)

# e2fsck -pf /dev/vg01/lvol0
/dev/vg01/lvol0 is mounted.
e2fsck: Cannot continue, aborting.

# umount /mydata

# e2fsck -pf /dev/vg01/lvol0
/dev/vg01/lvol0: 11/13328 files (0.0% non-contiguous), 6644/53248 blocks

# mount /dev/vg01/lvol0 /mydata

# df -T /mydata
Filesystem             Type 1K-blocks  Used Available Use% Mounted on
/dev/mapper/vg01-lvol0 ext4     47463   859     42878   2% /mydata

In the above output, we tried to run FS check while volume is mounted and it gave us an error. Finally, the file system upgraded to ext4 which can be verified in the last output. Make a note that this is irreversible change and you can not go back to ext3 once you did this upgrade.

There is another way as well to have a file system of ext4 as below –

ext4 file system is backward compatible with ext2 and ext3. This means you can directly mount any ext2 or ext3 filesystem as ext4 without upgrading. You just simply un-mount filesystem and mount it as ext4 by supplying -t switch with mount command.

# umount /mydata

# mount -t ext4 /dev/vg01/lvol0 /mydata

# df -T /mydata
Filesystem             Type 1K-blocks  Used Available Use% Mounted on
/dev/mapper/vg01-lvol0 ext4     47463   859     43942   2% /mydata

In the above output, we un-mount out ext3 mount point and remounted it as ext4! This process is reversible means you can un-mount the ext4 file system and re-mount it as ext3 again.

How to upgrade ext2 to ext4

As we saw above you need to enable file system features to upgrade to ext4. While upgrading from ext2 to ext4 you need to enable has_journal extra features than the above list. Since you know ext2 doesn’t have journaling available.

# umount /mydata

# tune2fs -O extents,uninit_bg,dir_index,has_journal /dev/vg01/lvol0
tune2fs 1.42.13 (17-May-2015)
Creating journal inode: done

# e2fsck -pf /dev/vg01/lvol0
/dev/vg01/lvol0: 11/13328 files (0.0% non-contiguous), 6627/53248 blocks

# mount /dev/vg01/lvol0 /mydata

# df -T /mydata
Filesystem             Type 1K-blocks  Used Available Use% Mounted on
/dev/mapper/vg01-lvol0 ext4     47463   842     42895   2% /mydata

Make a note that this is irreversible change and you can not go back to ext3 once you did this upgrade.

Another method would be directly mounting FS as ext4 as below –

As stated earlier, the ext4 file system is backward compatible with ext2 and ext3, means you can directly mount any ext2 or ext3 filesystem as ext4 without upgrading

# df -T /mydata
Filesystem             Type 1K-blocks  Used Available Use% Mounted on
/dev/mapper/vg01-lvol0 ext2     51559   842     48055   2% /mydata

# umount /mydata

# mount -t ext4 /dev/vg01/lvol0 /mydata

# df -T /mydata
Filesystem             Type 1K-blocks  Used Available Use% Mounted on
/dev/mapper/vg01-lvol0 ext4     51559   842     48055   2% /mydata

Previously ext2 file system is mounted as ext4 in the above output without upgrading!

How to check if Linux server is physical or VM or cloud

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Learn how to check if the Linux server is a physical or VM or cloud server by observing ‘dmidecode’ command output fields.

Recently one of my friends came across a situation where he didn’t know logged in the server is physical server, virtual machine, or cloud server. So here in this article we will walk you through how to check if the server is a physical server or virtual machine. Since cloud servers are also VM there is a very thin line between identifying them as different. It takes some infrastructure knowledge and sense to differentiate between VM and cloud-hosted servers.

dmidecode command helps you through this process. This command helps you to identify the manufacturer of the system. Let’s look at its output :

root@kerneltalks# dmidecode -t system
# dmidecode 3.0
Scanning /dev/mem for entry point.
SMBIOS 2.4 present.

Handle 0x0100, DMI type 1, 27 bytes
System Information
        Manufacturer: Xen
        Product Name: HVM domU
        Version: 4.2.amazon
        Serial Number: ec27c3cb-8e3b-8a30-4325-3f388b0fxxxx
        UUID: EC27C3CB-8E3B-8A30-4325-3F388B0Fxxxx
        Wake-up Type: Power Switch
        SKU Number: Not Specified
        Family: Not Specified
-----output trimmed-----

This is output from the AWS cloud server. In the above output you have to observe the ‘System Information‘ section.

Manufacturer :

If you see Xen, VMware, Red Hat, etc here its a VM (virtual machine). VM host KVM also shows the same manufacturers. Anything other than these like Dell Inc, HP, etc (hardware manufacturing companies name) shows that you are on real physical hardware means its physical server.

Product Name :

This parameter also helps further to confirm it’s physical or VM. Here HVM denotes its virtual machine clearly. For a physical server you see the physical server model name here.

Version :

Its again narrowing down your search. Word amazon here denotes its a VM from Amazon (most likely AWS). So as I said if you know your infrastructure well, so must be knowing you have AWS servers or not. And hence you can be sure here that it’s AWS cloud server.

Even serial numbers can be a confirmation but you should have in-depth knowledge of hardware serial number nomenclature used by industry manufacturers. Mostly, physical hardware has much short, clean and human-readable serial number whereas VM has long serial which starts with virtual service name (eg, ec2 for AWS cloud, VMWare for VMware VM, etc.) This can be added confirmation and not the primary parameter for validation.

For more understanding lets look at output from virtual machine :

root@kerneltalks_vm1# dmidecode -t system
# dmidecode 2.12
SMBIOS 2.4 present.

Handle 0x0001, DMI type 1, 27 bytes
System Information
        Manufacturer: VMware, Inc.
        Product Name: VMware Virtual Platform
        Version: None
        Serial Number: VMware-56 4d c7 47 54 09 d6 39-xx xx xx xx xx xx xx xx
        UUID: 564DC747-xxxx-D639-xxxx-xxxxxxxxxx
        Wake-up Type: Power Switch
        SKU Number: Not Specified
        Family: Not Specified
-----output trimmed-----

In above output,

The manufacturer is VMware Inc. which denotes its a VM. Product Name VMware Virtual Platform clearly states its VM

Like the cloud server above we do not have version value here. But the above two values are sufficient to confirm its a VM. These values put up by hardware or system image manufacturer hence can be blank at times.

Finally, before signing off lets check output from physical machine as well –

root@kerneltalks_phy # dmidecode -t system
# dmidecode 2.11
SMBIOS 2.7 present.

Handle 0x0001, DMI type 1, 27 bytes
System Information
        Manufacturer: Cisco Systems Inc
        Product Name: UCSB-B200-M3
        Version: 1
        Serial Number: XXXXXXXXXX
        UUID: 00000000-0000-0000-0000-000000000000
        Wake-up Type: Other
        SKU Number:
        Family:
-----output trimmed-----

Here,

The manufacturer is Cisco System Inc (who is hardware manufacturer) confirming its server hosted on bare metal.

Product Name is a UCSB-B200-M3 which is the model name of Cisco Blade. Confirms server is Cisco Blade hardware (Physical server)

Checks submitted by readers

Few readers posted these commands on social media comments.

lscpu: One can observe hypervisor vendor determine if its virtual or physical server

# lscpu |grep -i hypervisor
Hypervisor vendor:     Xen

hostnamectl: Works on a new distro like RHEL7. The virtualization field gives you an idea about if its physical or virtual.

root@kerneltalks # hostnamectl status |grep -i virtual
    Virtualization: xen

dmesg: Check for words like KVM, hvm, or virtual in boot messages. Here Xen virtualization detected confirming its a virtual box.

# dmesg |grep -i virtual
[    0.000000] Booting paravirtualized kernel on Xen HVM
[    1.403040] systemd[1]: Detected virtualization xen.
[    1.889088] xen_netfront: Initialising Xen virtual ethernet driver

Conclusion

System information like manufacturer, product name, version, the serial number can be used to observe and understand whether logged in the server is a physical server or VM (physically hosted or cloud).

If you have any other tricks or solid methods to confirm the server is physical or virtualized, please let us know in the comments below.

Difference between ext2, ext3 and ext4

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List of differences between ext2, ext3, and ext 4 Linux file systems. One of the Linux interview questions answered in this article!

This is another Linux interview question. What is the difference between ext2, ext3, and ext4 file systems? Or Explain Linux file system ext2 vs ext3 vs ext4? In this article we will walk through these differences and lastly I will present you all of them in tabular format so that they are easy to quickly read during your preparations.

Let’s see each file system’s features and lastly their comparison with other file systems.

EXT2 file system

It’s a second extended file system that was created to overcome limitations of the EXT file system.
Introduced in 1993 by Remy Card. It was the first commercial-grade filesystem for Linux
Does not supports Journaling
Fit for SD cards & USB drives since it has high performance and low writes (as journaling is not available). USB and SD storage are limited with write cycles hence its best fit for them.
Limits: Individual file size 16GB to 2TB. File system size 2TB to 32TB.

Limits are calculated based on block size used. Block size varies from 1KB to 8KB. For example, If 1KB block size is used max file size can go up to 16GB and for 8KB it’s 2TB. Middle range sizes being 2KB and 4KB which has file size limits of 256GB & 2TB (not mentioned in above limits) respectively. The same applies to the File system size limits defined above.

EXT3 file system

It’s third extended file system was created to overcome limitations of the EXT2 file system.
Introduced in 2001 by Stephen Tweedie. It was the most common filesystem in any Linux distro.
Supports Journaling
Journaling keeps track of file changes which helps in fast recovery and reduce chances of data loss in case of a system crash
Limits: Individual file size 16GB to 2TB. File system size 4TB to 32TB.
Upgrading FS from ext2 to ext3 is an online process without downtime.

EXT4 file system

It’s the fourth extended file system that was created to overcome limitations of the EXT3 file system.
Introduced in 2008 by a team of developers. Its most the latest filesystem in ext family.
Supports Journaling
Lots of new features introduced. Extents, Backward compatibility, Persistent pre-allocation, Delayed allocation, Unlimited number of subdirectories, Journal checksum, Faster FS check, Transparent encryption.
Limits: Individual file size 16GB to 16TB. File system size up to 1EB.
Upgrading FS not needed. Due to backward compatibility, ext2, ext3 can be directly mounted as ext4.

All above points can be formatted in tabular format as below :

Parameter	EXT2	EXT3	EXT4
Introduced year	1993	2001	2008
Developed by	Remy Card	Stephen Tweedie	Team of developers
Journaling	Not available	Available	Available
Individual file size	16GB to 2TB	16GB to 2TB	16GB to 16TB
File system size	2TB to 32TB	4TB to 32TB	up to 1EB
Upgrade	Can be done online to EXT3. Can be mounted as EXT4. No upgrade needed	Can be mounted as EXT4. No upgrade needed	NA