Disable colours on terminal and SSH

Question

My local Linux machine has coloured terminal output like this;

When I SSH to a pfSense/BSD box it changes the colours like this;

Even when I SSH from to a machine that doesn't have a coloured local terminal output, and SSH from there to this pfSense/FreeBSD box it enables coloured output, and starts producing unwanted coloured output/

Is there something I can change locally so that when I SSH to the pfSense box from either my local machine or via an intermediary machine, my client will ignore the remote colour settings. Ideally I want to stay in black and white, two tone standard background and text colour only?

Answer 1

Changing the TERM variable to some entry that is compatible but doesn't have colour support might work. Like:

TERM=xterm-old

Basically, you need a TERM known by the FreeBSD system termcap or terminfo database for which TERM=the-term tput colors doesn't return a positive number, and for GNU ls, one for which dircolors -p | grep -x 'TERM the-term' returns nothing. It may still not work for applications that output colour escape sequences regardless of whether the terminal claims to support it or not.

Alternatively, you could use GNU screen to disable colors, like (zsh syntax):

screen -c =(printf %s\\n "termcapinfo * 'AF=\E[1m:AB=\E[7m'") ssh ...

That would enable bold for every attempt to set the foreground colour and reverse for every attempt to set the background one.

I think it all boils down to the fact that FreeBSD assumes that the terminal background is black (or at least dark). Where you using xterm instead of xfce-terminal, you could dynamically change the background and foreground colour and/or the individual colours to set different colour profiles. That is done through escape sequences, but you can also use the xtermcontrol command that makes it easier.

Answer 2

Colours in your terminal appear because the tty sends ANSI-encoded control sequences to tell your terminal to change colours. Some, if not most terminal application can be configured to ignore this and just display all text in one colour.

In xterm, you can use the -cm option. For Konsole, one can change the mapping of all colours to the same. Your XFCE terminal application may have similar options.

Answer 3

In case you don't want to modify your ~/.bashrc which I'm sure contain something like export PS2=.....+colors...... :

On the linux Console, try either TERM=linux-m1b or TERM=linux-m2 to get monochrome as "Gray/White/Black and Dim" for linux-m1b or "Green/White/Black and Blue" (vintage!) for linux-m2 ...

With Putty (there is a port for Mac users), use TERM=putty-m1b and TERM=putty-m2 instead ...

This will do exactly what you need but: You'll need a recent terminfo database for that or get it from there if necessary: wget http://canal.chez.com/linux.ti ; tic -x linux.ti

Alex. PS: xterm-mono seems not to exist anymore.

Answer 4

Type the following command to remove it:

$ ls --color=none

or use unalias to remove it:

$ unalias ls

Answer 5

You should be able to convince your terminal emulator and environment that it cannot support colors in the first place, presuming your GNU/Linux system is not ignoring the rules:

unset LS_COLORS
TERM=xterm-mono
export TERM

Try using TERM=vt100 or TERM=xterm-mono in something like htop and you should immediately see the difference.

You could also quickly test by trying to toggle colors in top by pressing lowercase z.

---

Alternately, by combining some other contributors methods, you could get a list of "no-color" terminal definitions (-1) and pick one:

$ find /lib/terminfo -type f -exec sh -c 'for fx do T=`basename "$fx"` ;echo -n "$T ";TERM=$T tput colors ;done' find-sh {} + | sort -V | grep '\-1'

dumb -1
mach -1
mach-bold -1
mach-gnu -1
rxvt-basic -1
sun -1
vt52 -1
vt100 -1
vt102 -1
vt220 -1
xterm-mono -1
xterm-r5 -1
xterm-r6 -1

Answer 6

First, check your default alias:

alias

alias ls-'ls --color=auto

If the doesn't work and you need a quick workaround. Try this ls and awk pipe:

vi /usr/local/bin/list
#!/bin/bash
ls $1
exit

set the perms 744.
One safe place for this would be /usr/local/bin Make sure your PATH includes /usr/local/bin.

Again use discretion.

One thing… the colors are meant to flag directories… turning off the ls="ls --color=auto" leaves only names… ls -aF or ls -F will append the directory names with /. So I would suggest that you be aware. You could alias ls="ls -aF" or alias ls="ls -F".