Can't use terminal in Cloud9 (tmux: invalid LC_ALL, LC_CTYPE or LANG)

Question

I recently resized my EBS for my EC2 instance, because I was running out of space. See https://docs.aws.amazon.com/cloud9/latest/user-guide/move-environment.html#move-environment-resize.  
  
My instance has been resized, but I am no longer able to use the terminal in Cloud9. When I open a terminal instance, the following message repeatedly posts in an infinite loop:  
  
tmux: invalid LC_ALL, LC_CTYPE or LANG  
  
I am unable to use the terminal to run any commands to try to trouble shoot or address the issue. Any thoughts on what I can do?

Answer

Not a solution, but I ended up just copying down all of the files from the server that I could access in Cloud9's environment pane, and then I restored my clean volume backup and copied the files back over.

Answer

Not sure how my instance ended in described situation.  I might have expanded the EBS but it was a long time 
previous to this issue occuring.

I ended up following the suggestions here
https://docs.aws.amazon.com/cloud9/latest/user-guide/troubleshooting.html#tmux-terminal-error

I was able to start a shell using systems manager config described above.

Check the locale
```
locale -a
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_COLLATE to default locale: No such file or directory
C
C.utf8
POSIX
```
Some how UTF8 is no longer there ?
Looked in /usr/share/i18n/locales  - the locales appear to be there.

```
localedef -i en_US -f UTF-8 en_US.UTF-8

locale -a
C
C.utf8
POSIX
en_US.utf8
```
Find tmux, in my instance
/opt/c9/local/bin/tmux

Verify tmux will start up without error.

Restarted the instance and was able to launch the Cloud9 GUI and terminals were working again.

This also resolved a few other issues on the instance.

Can't use terminal in Cloud9 (tmux: invalid LC_ALL, LC_CTYPE or LANG)

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