"The Linux Gazette...making Linux just a little more fun!"

Files invisible via Telnet?

From Norris on Mon, 11 Oct 1999

First off, thank you for a good site, a real valuable source on all those little (and not so little) problems you run into

Second, im not sure if I should go and ask questions directly to you, but it seems others have done so, but if i am in error, please just ignore me

You did it right: mail to the [email protected]. It's a shame that so many people still send their questions to [email protected] (which is the same mailbox) because I can auto-sort LG mail from personal mail. However, that just comes with the territory.

The Problem:

I have allowed telnet acces to my server, and i can login fine, i can su and so forth, but a lot of files just dont show up via telnet? i have messed with many combinations of file permissions, but that doesnt seem to do it... any help would be appreciated, thank you

Linux and UNIX have no mechanism for selectively "hiding" files based on the protocol through which you've logged in. Unless you are running your telnet daemon or inetd in a "chroot jail" (a fairly obscure custom configuration) then you should be able to see everything.

Now, if you mean that some files don't appear to be readable through your terminal (you do an 'ls' and see "blanks" where there should be files) then that's another matter entirely. Trying using the command:

ls --color=never

... if your files are suddenly visible then you're just suffering from a bad terminal type (TERM environment variable) setting.

You could also try the commands:

export TERM=dumb find . | less

... (assuming you're using a Bourne compatible shell -- like the default 'bash'). This should show you all your files.

The 'ls --color' trick has to do with the ncurses color support in the GNU version of 'ls'. Some distributions set a system default alias like: alias ls='ls --color=auto' so that you'll see your files in pretty colors when using a color capable terminal (such as the console, or a color xterm). If your TERM environment variable is set correctly, and your terminfo libraries and data files are installed correctly then this alias should automatically disable the use of color when necessary.

Unfortunately the MS Windows version of TELNET.EXE is pretty wretched. It defaults to settings which do not implement enough VT100, VT220 or VT330 support to be usable for most Linux tasks. You're usually better off forcing that telnet client to use the older, less powerful VT52 mode. You'd be MUCH better off to replace it with a good telnet client, such at K'95 (The Win '95 port of Columbia University's Kermit package).

Of course I'm just guessing at what you mean by "invisible." It's possible that you are in a "chroot" jail (in which case you wouldn't see ANY files and directories "above" a certain point in the real directory tree. This would probably be quite confusing to you since you'd have to have duplicate /etc, /dev, and /usr/bin directory structures and filesets.

I've set up systems like that (in fact I've just configure my new personal workstation in this way this weekend). However it's a relatively obscure and advanced technique that almost no one uses. You couldn't have set that up "accidentally" or without knowing about it.

So I'm assuming the more likely interpretation of your question. (I usually have to do that in this business).

Copyright © 1999, James T. Dennis
Published in The Linux Gazette Issue 48 December 1999

HTML transformation by Heather Stern of Starshine Technical Services, http://www.starshine.org/

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