Having connected an external drive to my PC a Terminal window opened with the following text:
Last login: Thu Mar 3 14:29:13 on ttys000
The default interactive shell is now zsh.
To update your account to use zsh, please run `chsh -s /bin/zsh`.
For more details, please visit https://support.apple.com/kb/HT208050.
What does this mean?
MacBook Air 13″, macOS 11.6
The connection of an external drive to your Mac should not open a Terminal window without that being a deliberate act on your part.
Since 2007, Apple shipped the same Bash shell version that was the default for Terminal windows. Apple has switched to the MIT licensed, modern Zsh shell as its strategic supported SHELL product because the GPL3 licensing terms for newer Bash versions are unacceptable to Apple.
If you want to continue using the ancient default Bash shell in the Terminal, you can set the following in your Bash dot file in your home directory:
In /Users/yourname/.bash_profile, add the following:
export BASH_SILENCE_DEPRECATION_WARNING=1
and the next time the Terminal opens that changing your default shell message will not be present.
If you do decide to switch to the Zsh shell, run that indicated command in the Terminal, but you will need to set at minimum your PATH and terminal prompt in a new startup file (.zshrc) as the Zsh shell does not read the old Bash startup file contents. If you don't do any shell script programming, you probably won't notice a difference in using the Zsh shell, other than the default prompt is different.
The connection of an external drive to your Mac should not open a Terminal window without that being a deliberate act on your part.
Since 2007, Apple shipped the same Bash shell version that was the default for Terminal windows. Apple has switched to the MIT licensed, modern Zsh shell as its strategic supported SHELL product because the GPL3 licensing terms for newer Bash versions are unacceptable to Apple.
If you want to continue using the ancient default Bash shell in the Terminal, you can set the following in your Bash dot file in your home directory:
In /Users/yourname/.bash_profile, add the following:
export BASH_SILENCE_DEPRECATION_WARNING=1
and the next time the Terminal opens that changing your default shell message will not be present.
If you do decide to switch to the Zsh shell, run that indicated command in the Terminal, but you will need to set at minimum your PATH and terminal prompt in a new startup file (.zshrc) as the Zsh shell does not read the old Bash startup file contents. If you don't do any shell script programming, you probably won't notice a difference in using the Zsh shell, other than the default prompt is different.
If you do not normally use the Terminal, you can ignore the message.
Why am I asked about changing my default interactive shell?
