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
set completion-ignore-case on into the users's
~/.inputrc file, or the system
/etc/inputrc, to enable it for all users. This is the initialisation file for readline.
~/.inputrc probably doesn't exist, and you will have to create it, this will override the system copy at
/etc/inputrc. This has lots of useful key mappings configured, such as
The way to fix this problem is to put the line
$include /etc/inputrc at the top of
set completion-ignore-case on
Then either restart bash or reload inputrc, e.g. with Ctrlx,Ctrlr.)
More information about readline and inputrc can be found in
man bash and
man 3 readline.