You can do this by setting a configuration variable for GNU readline, which is what handles the input in an interactive shell.
The variable needed is
completion-ignore-case, and can be set directly in your bash session with:
bind "set completion-ignore-case on"
It can be enabled for all future bash sessions by putting it in the users's
~/.inputrc file, or the system
/etc/inputrc, to enable it for all users. This is the initialisation file for readline.
But note that if you create
~/.inputrc, this will override the system copy. (For me this caused me to lose some key mappings, such as
Right. You can see which ones by perusing the
The way to fix this problem is to put the line
$include /etc/inputrc at the top of
set completion-ignore-case on
To apply the changes, restart bash or reload inputrc, e.g. with Ctrl+x,Ctrl+r.
More information about readline and inputrc can be found in
man bash and
man 3 readline.