Cloud Vedas

Solved: Install Python 3 in Linux and set it as default

In this post we will show you how to install python 3 in a Linux box. We have Centos 7 installed in our server.
Check installed python version
Most of the Linux versions by default have python installed. So let's check the current version.

[ec2-user@cloudvedas ~]$ python --version
 Python 2.7.5
[ec2-user@cloudvedas ~]$

As we can see from the above output, currently we have Python 2 installed and we need Python 3 so let's install it.
Install pre-requisites
Before we install python 3 let's first update the yum.

[ec2-user@cloudvedas ~]$ sudo yum -y update

Also, install yum utils.

[ec2-user@cloudvedas ~]$ sudo yum -y install yum-utils

And at the end install the CentOS development tools which will help you build and compile software from source code.

[ec2-user@cloudvedas ~]$ sudo yum -y groupinstall development

Install python 3.6.4
The standard yum repos does not have the latest python release, so we will install IUM (Inline with Upstream Stable) which will have the latest packages.

[ec2-user@cloudvedas ~]$ sudo yum -y install https://centos7.iuscommunity.org/ius-release.rpm

Now let's install Python 3.6.

[ec2-user@cloudvedas ~]$ sudo yum -y install python36u

Next we will install pip, which will manage software packages for Python:

[ec2-user@cloudvedas ~]$ sudo yum -y install python36u-pip

Finally, we will install the development packages.

[ec2-user@cloudvedas ~]$ sudo yum -y install python36u-devel

Let' check our python version

[ec2-user@cloudvedas ~]$ python3.6 -V
Python 3.6.4
[ec2-user@cloudvedas ~]$

Update default python
But if you still run the normal command to check python version it will show the Python 2 version if it was installed by default.

[ec2-user@cloudvedas ~]$ python --version
 Python 2.7.5
 [ec2-user@cloudvedas ~]$

To reflect the new python version by default you create an alias in .bashrc file as described below in the last line of the file.

[ec2-user@cloudvedas ~]$ sudo vi ~/.bashrc

# .bashrc
# Source global definitions
if [ -f /etc/bashrc ]; then . /etc/bashrc fi
# Uncomment the following line if you don't like systemctl's auto-paging feature:
# export SYSTEMD_PAGER=
# User specific aliases and functions
alias python=python3.6

After making the changes save the file. Now, logout and login again, it should show you the new version.

[ec2-user@cloudvedas ~]$ python -V
Python 3.6.4
[ec2-user@cloudvedas ~]$

Check all installed python versions
Do remember that the default python 2 will still remain in the system as lot of system binaries have dependency on it.
To check all the python versions in your box you can check the installed packages as below.

[ec2-user@cloudvedas ~]$ yum list installed | grep -i python

If you want to create virtual environments in python read our next post.

Solve: How to add an EBS volume to a Windows EC2 instance and configure it

This post is divided in two sections. In the first section you will see how to create an EBS volume and in the next section we will show you how to configure the EBS volume in windows instance.
Create EBS Volume

Go to AWS Console > EC2
In the left panel select “Volumes” .
Once in the “Volume” screen select “Create Volume”
In the “Create Volume” window specify the size of disk and the Availability Zone in which you want the disk to be created.

Tip:- The disk should be in same AZ as your EC2 instance.

Now in the left pane again select the “Volume” to see all your volumes.
Select the volume you just created and after that in the upper menu click on “Actions” and select “Attach volume”
In “Attach volume” window select the instance to which you want to attach the volume and click on “Attach”.

Configure EBS volume in Windows

Login to your windows EC2 instance using RDP. Once inside the instance, from the Start menu go to “Computer Management” as mentioned below.

Start > Control Panel > System and Security > Administrative Tools > Computer Management

Click on Disk Management on the left pane.
Here we can see the new disk but it’s still offline. Right click on the new disk and select “Online”.

Once the disk is online right click again on the disk and select “Initialize Disk”.

If disk is below 2TB, select MBR and click OK

Finally right click on the pane where size is shown(refer image below). Select “New Simple Volume”

Leave other options as default and click “Next” till you come to “Assign Drive Letter or Path”. Here we have assigned the drive letter E .

Leave everything else as default in next windows and click on finish.

Now if we go to “This PC/ My computer” we should see the new disk.

So here we have attached an EBS volume to the Windows EC2 instance. Do let us know in comments section if you have any query.

How to sell other state car in India

When I planned to move from Gurgaon to Pune I was in dilemma over whether to sell my Gurgaon registered car in Gurgaon or take it with me to Pune.
Since the new company I was joining was paying for relocation so car shifting cost was not an issue.

Solved: How to extend or grow a linux filesystem under LVM

In this post we will see how to grow a Linux filesystem without reboot.

Let's check our current filesystem. We want to extend this filesystem by 200MB.

[root@cloudvedas CVFS1]# df -h /CVFS1
Filesystem                  Size Used Avail Use% Mounted on
/dev/mapper/cvsvg-cldvdsvol1 47M 12M    32M  26%   /CVFS1
[root@cloudvedas CVFS1]#

First check if we have free space in VG

[root@cloudvedas /]# vgs
 VG    #PV    #LV    #SN    Attr    VSize    VFree
 cvsvg  1      1      0      wz--n- 196.00m  144.00m
 rhel   1      3      0      wz--n- 7.51g    36.00m
[root@cloudvedas /]#

Since we don't have 200MB free in "cvsvg" so we will add a new disk to it. First label the disk for LVM and get it under LVM control using pvcreate.

[root@cloudvedas CVFS1]# pvcreate /dev/sdb2
 Physical volume "/dev/sdb2" successfully created
[root@cloudvedas CVFS1]#

Add the new partition to our VG.

[root@cloudvedas CVFS1]# vgextend cvsvg /dev/sdb2
 Volume group "cvsvg" successfully extended
[root@cloudvedas CVFS1]#

Check the VG size again.

[root@cloudvedas CVFS1]# vgs
 VG    #PV   #LV    #SN    Attr    VSize    VFree
 cvsvg  2     1      0     wz--n-  444.00m  392.00m
 rhel   1     3      0     wz--n-  7.51g    36.00m
[root@cloudvedas CVFS1]#

Now we have the required space so, let's extend the volume first.

[root@cloudvedas CVFS1]# lvextend -L +200M /dev/cvsvg/cldvdsvol1
 Size of logical volume cvsvg/cldvdsvol1 changed from 52.00 MiB (13 extents) to 252.00 MiB (63 extents).
 Logical volume cldvdsvol1 successfully resized

On checking the LV we can see it's now extended as is now of 252MB.

[root@cloudvedas CVFS1]# lvs
 LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
 cldvdsvol1 cvsvg -wi-ao---- 252.00m
 root rhel -wi-ao---- 6.67g
 swap rhel -wi-ao---- 820.00m
 testvol1 rhel -wi-a----- 4.00m
[root@cloudvedas CVFS1]#

Let's increase the filesystem now using resize2fs.

[root@cloudvedas CVFS1]# resize2fs /dev/cvsvg/cldvdsvol1
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/cvsvg/cldvdsvol1 is mounted on /CVFS1; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/cvsvg/cldvdsvol1 is now 258048 blocks long.

Check the file system now.

[root@cloudvedas CVFS1]# df -h /CVFS1
Filesystem                   Size Used Avail Use% Mounted on
/dev/mapper/cvsvg-cldvdsvol1 241M  13M  217M  6%   /CVFS1
[root@cloudvedas CVFS1]#

Great so we have now extended the filesystem.

Solved: How to label a disk in Linux

In this post we will see how to label a new disk in Linux and create a new LVM partition.
Step 1 Scan the new LUNS.
Step 2 List the available disks and identify the one you want to use.

  fdisk -l |grep /dev/ |grep -v dm

Step 3 Use fdisk to label the disk. Here we are using disk sdb .

[root@cloudvedas scsi_host]# fdisk /dev/sdb
 Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
 Be careful before using the write command.

Device does not contain a recognized partition table
 Building a new DOS disklabel with disk identifier 0x909f2c7b.

Command (m for help): p

Disk /dev/sdb: 1073 MB, 1073741824 bytes, 2097152 sectors
 Units = sectors of 1 * 512 = 512 bytes
 Sector size (logical/physical): 512 bytes / 512 bytes
 I/O size (minimum/optimal): 512 bytes / 512 bytes
 Disk label type: dos
 Disk identifier: 0x909f2c7b

Device Boot Start End Blocks Id System

Command (m for help):

Step 4 Create Primary partition using option "n" of size 200MB.

Command (m for help): n
 Partition type:
 p primary (0 primary, 0 extended, 4 free)
 e extended
 Select (default p): p
 Partition number (1-4, default 1):
 First sector (2048-2097151, default 2048):
 Using default value 2048
 Last sector, +sectors or +size{K,M,G} (2048-2097151, default 2097151): +200M
 Partition 1 of type Linux and of size 200 MiB is set

(Don't miss the + used before 200M. It's very critical else it won't work as expected)
Step 4 Now let's check our new partition

Command (m for help): p

Disk /dev/sdb: 1073 MB, 1073741824 bytes, 2097152 sectors
 Units = sectors of 1 * 512 = 512 bytes
 Sector size (logical/physical): 512 bytes / 512 bytes
 I/O size (minimum/optimal): 512 bytes / 512 bytes
 Disk label type: dos
 Disk identifier: 0xc1c8c781

Device Boot Start End Blocks Id System
 /dev/sdb1 2048 411647 204800 83 Linux

Command (m for help):

Step 5 In the above output we can see that the new partition is a standard linux partition. Let's Change the partition type to Linux LVM. Here we will use "8e" which is a Hex code for LVM. You can type L to list all codes.

Command (m for help): t
 Selected partition 1
 Hex code (type L to list all codes): 8e

-Changed type of partition 'Linux' to 'Linux LVM'

Command (m for help): p

Disk /dev/sdb: 1073 MB, 1073741824 bytes, 2097152 sectors
 Units = sectors of 1 * 512 = 512 bytes
 Sector size (logical/physical): 512 bytes / 512 bytes
 I/O size (minimum/optimal): 512 bytes / 512 bytes
 Disk label type: dos
 Disk identifier: 0xc1c8c781

Device Boot Start End Blocks Id System
 /dev/sdb1 2048 411647 204800 8e Linux LVM

Command (m for help):

Step 6 Finally save the changes with option "w"

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

Step 7 Let's list the partition table to cross check that our partition table is saved correctly.

[root@cloudvedas /]# fdisk -l /dev/sdb

Disk /dev/sdb: 1073 MB, 1073741824 bytes, 2097152 sectors
 Units = sectors of 1 * 512 = 512 bytes
 Sector size (logical/physical): 512 bytes / 512 bytes
 I/O size (minimum/optimal): 512 bytes / 512 bytes
 Disk label type: dos
 Disk identifier: 0x0aa5ab95

Device Boot Start End Blocks Id System
 /dev/sdb1 2048 411647 204800 8e Linux LVM
 [root@cloudvedas /]#

Cool! So, we have now a LVM partition which we can bring under LVM control using pvcreate.