Mdthbs

I've run into a peculiar issue on a fresh gentoo install. Within the console, the Backspace key prints an adorable little question mark inscribed within a square instead of its intended function. Also, I've found that Tab behaves in exactly the same way, in addition to any Ctrl commands. The keys worked perfectly fine during the install, but after booting into the system proper and performing initial setup, they seem to have just given up.

localectl status outputs the following:

System Locale: LANG=en_US.utf8 

               LC_COLLATE=C 

    VC Keymap: us 

   X11 Layout: us 

    X11 Model: pc105+inet 

  X11 Options: terminate:ctrl_alt_bksp

Basically, I can't use the Backspace or Ctrl keys in console and haven't yet installed x11. I'm stuck. Any ideas?

Ran out of space as a comment..

For backspace, stty erase '^?' should get you what you want.

When you say CTRL commands aren't working, do you mean CTRL+C? If so, what about stty intr ^C? Can you still switch terminals with CTRL+ALT+F#? In any case, it may be helpful to paste the output of stty -a

The following link should be helpful when it comes to stty settings:
http://docstore.mik.ua/orelly/unix3/upt/ch05_08.htm

Also, another question: since you're using the localectl command, does that mean you're running systemd? Did the install disk use systemd or openRC? I'm pretty sure it's openRC and that might be why it worked in the installer and not in the OS.

The question-mark-in-a-box is the Unicode replacement character. The Linux console will print that in two cases:

• the character is not in the currently-loaded font (512 glyphs), or


• the display-controls feature has been enabled in the console.

The latter has been in the kernel quite a while, as seen in this link to console.c in 2.2.26, which has the relevant comment:

1869                 /* If the original code was a control character we

1870                  * only allow a glyph to be displayed if the code is

1871                  * not normally used (such as for cursor movement) or

1872                  * if the disp_ctrl mode has been explicitly enabled.

1873                  * Certain characters (as given by the CTRL_ALWAYS

1874                  * bitmap) are always displayed as control characters,

1875                  * as the console would be pretty useless without

1876                  * them; to display an arbitrary font position use the

1877                  * direct-to-font zone in UTF-8 mode.

1878                  */

and it is set by either of two escape sequences:

1051                         case 11: /* ANSI X3.64-1979 (SCO-ish?)

1052                                   * Select first alternate font, lets

1053                                   * chars < 32 be displayed as ROM chars.

1054                                   */

1055                                 translate = set_translate(IBMPC_MAP,currcons);

1056                                 disp_ctrl = 1;

1057                                 toggle_meta = 0;

1058                                 break;

1059                         case 12: /* ANSI X3.64-1979 (SCO-ish?)

1060                                   * Select second alternate font, toggle

1061                                   * high bit before displaying as ROM char.

1062                                   */

1063                                 translate = set_translate(IBMPC_MAP,currcons);

1064                                 disp_ctrl = 1;

1065                                 toggle_meta = 1;

1066                                 break;

and reset by a third:

1040                         case 10: /* ANSI X3.64-1979 (SCO-ish?)

1041                                   * Select primary font, don't display

1042                                   * control chars if defined, don't set

1043                                   * bit 8 on output.

1044                                   */

1045                                 translate = set_translate(charset == 0

1046                                                 ? G0_charset

1047                                                 : G1_charset,currcons);

1048                                 disp_ctrl = 0;

1049                                 toggle_meta = 0;

1050                                 break;

The last (if TERM is linux) can be scripted as

tput rmpch

using this feature:

   exit_pc_charset_mode      rmpch    S3   Exit PC character

                                           display mode

or

tput sgr0

but not the reset or stty commands.

Further reading:

• console_codes - Linux console escape and control sequences


• terminfo building block klone+sgr, containing rmpch
  


• terminfo - terminal capability data base