WARNING: /bin/sh is not bash! - No tftp server found

I need to launch Petalinux but I get warning that /bin/sh is not bash !

Here is the terminal.

abc@alpha:/scratch2/abc/Xilinx$ source Petalinux/settings.sh
PetaLinux environment set to '/scratch2/abc/Xilinx/Petalinux'
WARNING: /bin/sh is not bash! 
bash is PetaLinux recommended shell. Please set your default shell to bash.
WARNING: This is not a supported OS
INFO: Checking free disk space
INFO: Checking installed tools
INFO: Checking installed development libraries
INFO: Checking network and other services
WARNING: No tftp server found - please refer to "UG1144 2021.1 PetaLinux Tools Documentation Reference Guide" for its impact and solution
abc@alpha:/scratch2/abc/Xilinx$ 

Then I tried to run chsh -s /bin/bash but it says that user 'abc' does not exist in etc/passwd

abc@alpha:/scratch2/abc/Xilinx/Petalinux$ chsh -s /bin/bash
Password: 
chsh: user 'abc' does not exist in /etc/passwd

Then I tried to add user with a command passwd abc. It ask me current and new password. Which current password should I use here ? I tried to use the password of user 'abc' as current and some other as new password but then it says Authentication token manipulation error and password unchanged.

abc@alpha:/scratch2/abc/Xilinx/Petalinux$ passwd abc
Current Password: 
New password: 
BAD PASSWORD: The password is shorter than 8 characters
New password: 
Retype new password: 
passwd: Authentication token manipulation error
passwd: password unchanged
abc@alpha:/scratch2/abc/Xilinx/Petalinux$ 

When you first open your terminal issue the command:

echo $SHELL

That will tell you what shell you are using. If it’s /bin/sh you can switch to bash by just typing :

bash

Then you can try the commands that gave you warnings. If you still don’t have a tftp server refer to the documentation as suggested by the warning message. You may need to install something or start a service