how to install and configure aws cli on linux ?

AWS Command Line Interface (CLI). Depending on your operating system ways are different for installation. I will show you installation of AWS CLI on Ubuntu and CentOS Linux OS.

Install AWS Command Line Interface ( CLI)

 Install AWS CLI in Ubuntu Linux

Pip is recommended method of installing AWS CLI on Linux which is python based tool helps in install, upgrade, and remove Python packages.

– Install python-pip package using apt-get

[root@linuxforfreshers~] apt-get install python-pip

Install AWS CLI using pip command

[root@linuxforfreshers~] pip install awscli

– Configure AWS CLI

You can configure it using “aws configure” command.

While configuring, it will ask you for the several information like AWS Access Key ID, AWS Secret Access Key, Default region name, Default output format. You need to provide that information. In my case below is the Access Key and Secret Access Key.

AWS Access Key = AKIAJRSF3SHFXWALVL2A

AWS Secret Access Key = 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

Let’s configure it using command.

[root@linuxforfreshers~] aws configure

AWS Access Key ID [None]: AKIAJRSF3SHFXWALVL2A

AWS Secret Access Key [None]: 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

Default region name [None]: us-east-1

Default output format [None]:

[root@linuxforfreshers~]

Once configuration complete, It will create .aws folder in user’s home directory. Below is the content of .aws directory.

[root@linuxforfreshers~] ls .aws/

Config Credentials

[root@linuxforfreshers~] cat .aws/config

[default]

region = us-east-1

[root@linuxforfreshers~] cat .aws/credentials

[default]

aws_access_key_id = AKIAJRSF3SHFXWALVL2A

aws_secret_access_key = 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

[root@linuxforfreshers~]

 – Now Test if AWS CLI is installed correctly or not.

[root@linuxforfreshers~] aws help

If you are given wrong access_key u will get following error.

An error occurred (InvalidAccessKeyId) when calling the ListBuckets operation: The AWS Access Key Id you provided does not exist in our records.

– Check Version of AWS CLI.

[root@linuxforfreshers]aws --version

aws-cli/1.11.129 Python/2.7.6 Linux/4.4.0-59-generic botocore/1.5.92

Install AWS CLI in CentOS Linux

– Check if python is installed in your system or not. If not install it using below command.

[root@linuxforfreshers~]# yum -y install python

– Install Pip on Linux.

Download the installation script.

[root@linuxforfreshers~]# curl -O https://bootstrap.pypa.io/get-pip.py

  % Total    % Received % Xferd  Average Speed   Time    Time        Time  Current

                                    Dload  Upload   Total   Spent    Left  Speed

100 1388k  100 1388k    0       0   205k      0  0:00:06  0:00:06 --:--:--  265k

[root@linuxforfreshers~]#

Run the script with Python.

[root@linuxforfreshers~]# python get-pip.py

  Downloading pip-7.0.3-py2.py3-none-any.whl (1.1MB)

    100% |████████████████████████████████| 1.1MB 155kB/s

Collecting wheel

  Downloading wheel-0.24.0-py2.py3-none-any.whl (63kB)

    100% |████████████████████████████████| 65kB 252kB/s

Collecting argparse (from wheel)

  Downloading argparse-1.3.0-py2.py3-none-any.whl

Installing collected packages: pip, argparse, wheel

Successfully installed argparse-1.3.0 pip-7.0.3 wheel-0.24.0

[root@linuxforfreshers~]#

– Now install AWS command line using pip.

[root@linuxforfreshers~]# pip install awscli

– Let’s configure AWS CLI.

[root@linuxforfreshers~] aws configure

AWS Access Key ID [None]: AKIAJRSF3SHFXWALVL2A

AWS Secret Access Key [None]: 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

Default region name [None]: us-east-1

Default output format [None]:

[root@linuxforfreshers~]

– Verify either file and folder is created.

[root@linuxforfreshers~] ls .aws/

Config Credentials

[root@linuxforfreshers~] cat .aws/config

[default]

region = us-east-1

[root@linuxforfreshers~] cat .aws/credentials

[default]

aws_access_key_id = AKIAJRSF3SHFXWALVL2A

aws_secret_access_key = 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

[root@linuxforfreshers~]

Installation is complete now and you can start using aws cli.

How to kill defunct or zombie process in linux?

 HOW TO KILL DEFUNCT OR ZOMBIE PROCESS

A "defunct" processes is also known as a "zombie" processes. A Zombie process is referred as dead process which is receding on your system though it’s completed executing. In one shot we can say it’s a dead processes which is still in RAM. This process will be in your process table and consuming your memory. Having more defunct process will consume your memory which intern slows your system. We have to kill the defunct process in order to free RAM and make system stable.

What is a zombie process?

When a process finishes execution, it will have an exit status to report to its parent process. Because of this last little bit of information, the process will remain in the operating system’s process table as a zombie process, indicating that it is not to be scheduled for further execution, but that it cannot be completely removed (and its process ID cannot be reused) until it has been determined that the exit status is no longer needed.

When a child exits, the parent process will receive a SIGCHLD signal to indicate that one of its children has finished executing; the parent process will typically call the wait() system call at this point. That call will provide the parent with the child’s exit status, and will cause the child to be reaped, or removed from the process table.

Why defunct process are created?

Ans : When ever a process ends all the memory used by that process are cleared and assigned to new process but due to programming errors/bugs some processes are still left in process table. These are created when there is no proper communication between parent process and child proces

How do I remove zombie processes from a system?

Well, first you can wait. It’s possible that the parent process is intentionally leaving the process in a zombie state to ensure that future children that it may create will not receive the same pid. Or perhaps the parent is occupied, and will reap the child process momentarily.

Secondly, you can send a SIGCHLD signal to the parent (“kill -s SIGCHLD <ppid>“). This will cause well-behaving parents to reap their zombie children.

Finally, you can kill the parent process of the zombie. At that point, all of the parent’s children will be adopted by the init process (pid 1), which periodically runs wait() to reap any zombie children. Then system need reboot to kill zombie process.

Interview questions & answers

1. How to find a defunct process?

Ans : Using ps command

#ps -ef | grep defunct

Or

Run “ps aux” and look for a Z in the STAT column.

Or

ps aux | awk '"[Zz]" ~ $8 { printf("%s, PID = %d\n", $8, $2); }'

2. How can I kill a defunct process?

Ans : Just use kill command

#kill defunct-pid

3. Still not able to kill?

Ans : Then use kill -9 to force kill that process

#kill -9 defunct-pid

4. Still have an issue in killing it?

Ans : Then try to kill it’s parent id and then defunct.

#kill parent-id-of-defunct-pid

Then

#kill -9 parent-id-of-defunct-pid

5. Still having defunct?

Ans : If you still find defunct process eating up RAM then last and final solution is to reboot your machine(This is not preferred on production boxes).

6.What is orphan process?

Ans : An orphan process is said to be a process which runs through parent process is terminated, these process do not know what to do and when to terminate.

7. What is difference between orphan and defunct processes?

Ans : A defunct process is a dead process where there is no execution happening whereas orphan process is a live process which is still in execution state but don't have parent process

How to check which libraries are used by a program or process on Linux ?

Check shared library dependencies of a program executable

To find out what libraries a particular executable depends on, you can use ldd command. This command invokes dynamic linker to find out library dependencies of an executable.

Syntax:

ldd /path/to/program

Example:

[ram@linuxforfreshers.com]$ldd /usr/bin/ssh

            linux-vdso.so.1 =>  (0x00007ffe099dc000)

            libselinux.so.1 => /lib/x86_64-linux-gnu/libselinux.so.1 (0x00007f578f64a000)

            libcrypto.so.1.0.0 => /lib/x86_64-linux-gnu/libcrypto.so.1.0.0 (0x00007f578f26e000)

            libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f578f069000)

            libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f578ee50000)

            libresolv.so.2 => /lib/x86_64-linux-gnu/libresolv.so.2 (0x00007f578ec35000)

            libgssapi_krb5.so.2 => /usr/lib/x86_64-linux-gnu/libgssapi_krb5.so.2 (0x00007f578e9ed000)

            libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f578e628000)

            libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f578e3ea000)

            /lib64/ld-linux-x86-64.so.2 (0x000055f5ccd53000)

            libkrb5.so.3 => /usr/lib/x86_64-linux-gnu/libkrb5.so.3 (0x00007f578e11e000)

            libk5crypto.so.3 => /usr/lib/x86_64-linux-gnu/libk5crypto.so.3 (0x00007f578deef000)

            libcom_err.so.2 => /lib/x86_64-linux-gnu/libcom_err.so.2 (0x00007f578dceb000)

            libkrb5support.so.0 => /usr/lib/x86_64-linux-gnu/libkrb5support.so.0 (0x00007f578dadf000)

            libkeyutils.so.1 => /lib/x86_64-linux-gnu/libkeyutils.so.1 (0x00007f578d8db000)

            libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f578d6bc000)

Note that it is NOT recommended to run ldd with any untrusted third-party executable because some versions of ldd may directly invoke the executable to identify its library dependencies, which can be security risk.

Instead, a safer way to show library dependencies of an unknown application binary is to use the following command.

Syntax:

objdump -p /path/to/program

Example:

[ram@linuxforfreshers.com]$objdump -p /usr/bin/ssh | grep NEEDED

  NEEDED               libselinux.so.1

  NEEDED               libcrypto.so.1.0.0

  NEEDED               libdl.so.2

  NEEDED               libz.so.1

  NEEDED               libresolv.so.2

  NEEDED               libgssapi_krb5.so.2

  NEEDED               libc.so.6

Check shared library dependencies of a running process

If you want to find out what shared libraries are loaded by a running process, you can use pldd command, which shows all shared objects loaded into a process at run-time.

Syntax:

sudo pmap <PID>

Method 2: Using lsof

Syntax:

 lsof -P -T -p Application_PID

How to install tcsh or csh shell on a Debian or Ubuntu Linux ?

Cshell is a shell (command interpreter) with C-like syntax.

csh is a command language interpreter incorporating a history mechanism , job control facilities , interactive file name and user name completion, and a C-like syntax. It is used both as an interactive login shell and a shell script command processor. tcsh is an enhanced but completely compatible version of the Berkeley UNIX C shell.

"tcsh" advantages

   - The ability to use multiline aliases and exec statements in a reliable and consistent way.                          (Hense "sh" scripts can be  re-written as tcsh scripts with aliases instead of functions.)

   - "tcsh" is the same on all machines.  For "csh" I typically  have to modify scripts for different machines.  [example: HP-UX  "set nonomatch" needs to be replaced by "set nonomatch = ()"] 

   - source code is freely available

   - PWD and other common environmental variables are always defined. With "csh" this depends on the machine.

In most cases csh / tcsh is installed by default. All you have to do is type shell name to start using it:

$ csh

OR

$ tcsh

Install csh / tcsh

In case csh is not installed, type the following command at shell prompt as per your Linux distro / version.

Install it on Debian/Ubuntu/Mint Linux

$ sudo apt-get install csh

Install it on CentOS/RHEL

# yum install tcsh

Install it on Fedora Linux

$ sudo dnf install tcsh

Set csh as default login shell

To make csh as default login shell, type the following command:

$ which tcsh

OR

$ which csh

Sample output:

/bin/csh

Note down the /bin/csh or /bin/tcsh path. To change the shell simply type

$ chsh

OR

$ chsh -s /bin/csh

How do I display the list of loaded Linux Kernel modules or device drivers on Linux ?

You need to use lsmod program which show the status of loaded modules in the Linux Kernel. Linux kernel use a term modules for all hardware device drivers.Please note that lsmod is a trivial program which nicely formats the contents of the /proc/modules, showing what kernel modules are currently loaded.

Module Commands

There are a few commands that allow you to maniuplate the kernel. Each is quickly described below, for more information say `man [command]`.

• depmod - handle dependency descriptions for loadable kernel modules.
• insmod - install loadable kernel module.
• lsmod - list loaded modules.
• modinfo - display information about a kernel module.
• modprobe - high level handling of loadable modules.
• rmmod - unload loadable modules.

List or display loaded modules

Method 1: less /proc/modules

EXAMPLE:

ram@linuxforfreshers.com#less /proc/modules

uas 24576 0 - Live 0x0000000000000000

usb_storage 69632 1 uas, Live 0x0000000000000000

bridge 126976 0 - Live 0x0000000000000000

stp 16384 1 bridge, Live 0x0000000000000000

llc 16384 2 bridge,stp, Live 0x0000000000000000

xt_CHECKSUM 16384 3 - Live 0x0000000000000000

ipt_MASQUERADE 16384 9 - Live 0x0000000000000000

nf_nat_masquerade_ipv4 16384 1 ipt_MASQUERADE, Live 0x0000000000000000

ebtable_nat 16384 0 - Live 0x0000000000000000

ebtables 36864 1 ebtable_nat, Live 0x0000000000000000

nf_log_ipv4 16384 0 - Live 0x0000000000000000

nf_log_common 16384 1 nf_log_ipv4, Live 0x0000000000000000

xt_tcpudp 16384 13 - Live 0x0000000000000000

ip6table_mangle 16384 0 - Live 0x0000000000000000

iptable_nat 16384 1 - Live 0x0000000000000000

nf_conntrack_ipv4 16384 3 - Live 0x0000000000000000

Method 2: lsmod

Example:

ram@linuxforfreshers.com# lsmod  | tail -10

hid_generic            16384  0

usbhid                 49152  0

psmouse               126976  0

hid                   118784  2 hid_generic,usbhid

pata_acpi              16384  0

floppy                 73728  0

fjes                   28672  0

e1000e                233472  0

ptp                    20480  1 e1000e

pps_core               20480  1 ptp

Finding more info about any module or driver

Using Modinfo

Syntax: modinfo driver-Name-Here

Example:

ram@linuxforfreshers.com#modinfo e1000e

filename:       /lib/modules/4.4.0-59-generic/kernel/drivers/net/ethernet/intel/e1000e/e1000e.ko

version:        3.2.6-k

license:        GPL

description:    Intel(R) PRO/1000 Network Driver

author:         Intel Corporation, <linux.nics@intel.com>

srcversion:     8D9E9AFD67E40CA48E61582

alias:          pci:v00008086d000015D6sv*sd*bc*sc*i*

alias:          pci:v00008086d000015E3sv*sd*bc*sc*i*

alias:          pci:v00008086d000015D8sv*sd*bc*sc*i*

alias:          pci:v00008086d000015D7sv*sd*bc*sc*i*

alias:          pci:v00008086d000015B9sv*sd*bc*sc*i*

alias:          pci:v00008086d000015B8sv*sd*bc*sc*i*

alias:          pci:v00008086d000015B7sv*sd*bc*sc*i*

alias:          pci:v00008086d00001570sv*sd*bc*sc*i*

alias:          pci:v00008086d0000156Fsv*sd*bc*sc*i*

alias:          pci:v00008086d000015A3sv*sd*bc*sc*i*

alias:          pci:v00008086d000015A2sv*sd*bc*sc*i*

alias:          pci:v00008086d000015A1sv*sd*bc*sc*i*

alias:          pci:v00008086d000015A0sv*sd*bc*sc*i*

alias:          pci:v00008086d00001559sv*sd*bc*sc*i*

alias:          pci:v00008086d0000155Asv*sd*bc*sc*i*

alias:          pci:v00008086d0000153Bsv*sd*bc*sc*i*

alias:          pci:v00008086d0000153Asv*sd*bc*sc*i*

alias:          pci:v00008086d00001503sv*sd*bc*sc*i*

alias:          pci:v00008086d00001502sv*sd*bc*sc*i*

alias:          pci:v00008086d000010F0sv*sd*bc*sc*i*

alias:          pci:v00008086d000010EFsv*sd*bc*sc*i*

alias:          pci:v00008086d000010EBsv*sd*bc*sc*i*

alias:          pci:v00008086d000010EAsv*sd*bc*sc*i*

alias:          pci:v00008086d00001525sv*sd*bc*sc*i*

alias:          pci:v00008086d000010DFsv*sd*bc*sc*i*

alias:          pci:v00008086d000010DEsv*sd*bc*sc*i*

alias:          pci:v00008086d000010CEsv*sd*bc*sc*i*

alias:          pci:v00008086d000010CDsv*sd*bc*sc*i*

alias:          pci:v00008086d000010CCsv*sd*bc*sc*i*

alias:          pci:v00008086d000010CBsv*sd*bc*sc*i*

alias:          pci:v00008086d000010F5sv*sd*bc*sc*i*

alias:          pci:v00008086d000010BFsv*sd*bc*sc*i*

alias:          pci:v00008086d000010E5sv*sd*bc*sc*i*

alias:          pci:v00008086d0000294Csv*sd*bc*sc*i*

alias:          pci:v00008086d000010BDsv*sd*bc*sc*i*

alias:          pci:v00008086d000010C3sv*sd*bc*sc*i*

alias:          pci:v00008086d000010C2sv*sd*bc*sc*i*

alias:          pci:v00008086d000010C0sv*sd*bc*sc*i*

alias:          pci:v00008086d00001501sv*sd*bc*sc*i*

alias:          pci:v00008086d00001049sv*sd*bc*sc*i*

alias:          pci:v00008086d0000104Dsv*sd*bc*sc*i*

alias:          pci:v00008086d0000104Bsv*sd*bc*sc*i*

alias:          pci:v00008086d0000104Asv*sd*bc*sc*i*

alias:          pci:v00008086d000010C4sv*sd*bc*sc*i*

alias:          pci:v00008086d000010C5sv*sd*bc*sc*i*

alias:          pci:v00008086d0000104Csv*sd*bc*sc*i*

alias:          pci:v00008086d000010BBsv*sd*bc*sc*i*

alias:          pci:v00008086d00001098sv*sd*bc*sc*i*

alias:          pci:v00008086d000010BAsv*sd*bc*sc*i*

alias:          pci:v00008086d00001096sv*sd*bc*sc*i*

alias:          pci:v00008086d0000150Csv*sd*bc*sc*i*

alias:          pci:v00008086d000010F6sv*sd*bc*sc*i*

alias:          pci:v00008086d000010D3sv*sd*bc*sc*i*

alias:          pci:v00008086d0000109Asv*sd*bc*sc*i*

alias:          pci:v00008086d0000108Csv*sd*bc*sc*i*

alias:          pci:v00008086d0000108Bsv*sd*bc*sc*i*

alias:          pci:v00008086d0000107Fsv*sd*bc*sc*i*

alias:          pci:v00008086d0000107Esv*sd*bc*sc*i*

alias:          pci:v00008086d0000107Dsv*sd*bc*sc*i*

alias:          pci:v00008086d000010B9sv*sd*bc*sc*i*

alias:          pci:v00008086d000010D5sv*sd*bc*sc*i*

alias:          pci:v00008086d000010DAsv*sd*bc*sc*i*

alias:          pci:v00008086d000010D9sv*sd*bc*sc*i*

alias:          pci:v00008086d00001060sv*sd*bc*sc*i*

alias:          pci:v00008086d000010A5sv*sd*bc*sc*i*

alias:          pci:v00008086d000010BCsv*sd*bc*sc*i*

alias:          pci:v00008086d000010A4sv*sd*bc*sc*i*

alias:          pci:v00008086d0000105Fsv*sd*bc*sc*i*

alias:          pci:v00008086d0000105Esv*sd*bc*sc*i*

depends:        ptp

intree:         Y

vermagic:       4.4.0-59-generic SMP mod_unload modversions

parm:           debug:Debug level (0=none,...,16=all) (int)

parm:           copybreak:Maximum size of packet that is copied to a new buffer on receive (uint)

parm:           TxIntDelay:Transmit Interrupt Delay (array of int)

parm:           TxAbsIntDelay:Transmit Absolute Interrupt Delay (array of int)

parm:           RxIntDelay:Receive Interrupt Delay (array of int)

parm:           RxAbsIntDelay:Receive Absolute Interrupt Delay (array of int)

parm:           InterruptThrottleRate:Interrupt Throttling Rate (array of int)

parm:           IntMode:Interrupt Mode (array of int)

parm:           SmartPowerDownEnable:Enable PHY smart power down (array of int)

parm:           KumeranLockLoss:Enable Kumeran lock loss workaround (array of int)

parm:           WriteProtectNVM:Write-protect NVM [WARNING: disabling this can lead to corrupted NVM] (array of int)

parm:           CrcStripping:Enable CRC Stripping, disable if your BMC needs the CRC (array of int)

Method 3:

Using following command to find list of installed drivers.

ls -l /lib/modules/$(uname -r)/kernel/drivers/

Example:

ram@linuxforfreshers.com#ls  /lib/modules/$(uname -r)/kernel/drivers/ | tail -10

usb

uwb

vfio

vhost

video

virtio

vme

w1

watchdog

xen

What is the standard directory for driver files are stored?

Using following command u can get standard Directory for Driver files are stored.

echo "Kernel drivers dir: \"/lib/modules/$(uname -r)/kernel/drivers/\" \ for Linux kernel version \"$(uname -r)\" "

Example:

ram@linuxforfreshers.com#echo "Kernel drivers dir: \"/lib/modules/$(uname -r)/kernel/drivers/\" \ for Linux kernel version \"$(uname -r)\" "

Kernel drivers dir: "/lib/modules/4.4.0-59-generic/kernel/drivers/" \ for Linux kernel version "4.4.0-59-generic"