Try this in a console **as root**:
ln -f /dev/ttyS4 /dev/modem
If that doesn't work, try the same thing except use /dev/ttyS0, 1, 2, or 3.
Hi! Today I was instaled Knoppix 3.4 on my HDD.
I have intel 537 modem. Drivers are downloaded & unpacked.
I have log in as root and compiled drivers:
make clean
make all
make inastall
I have set up KPPP and IT IS WORKING!!!!!!!!!!!!
Avaj, then I have loged in as User, opened KPPP and dial.
Then it says: "Unable to open modem". All settings are same, modem is in /dev/ but I can dial only in root user. HELP!!!!!!!
Try this in a console **as root**:
ln -f /dev/ttyS4 /dev/modem
If that doesn't work, try the same thing except use /dev/ttyS0, 1, 2, or 3.
After installing to my hard drive, all was well. Then I uninstalled a few packages I didn't need. The next time I tried to dial out I got the message, "unable to open modem." I found that the mode for /dev/ttyS0,1,and 2 had been reset to c _ _ _ _ _ _ _ _ _. I changed the mode back to crw-rw-rw-, and all was well again.

KNOPPIX 9.1 Linux Install & Live DVD 32bit & 64bit
$19.99
Knoppix Live GNU Linux System 9.1 on Bootable CD / DVD / USB Flash Drive
$10.99
Windows XP, Vista, 8.1, Linux Knoppix, Office XP, (6 CDS)
$10.00
KNOPPIX USB DVD OS , BEST OF ALL HIGHLY RECOMENDED
$11.99
Knoppix Linux Bootable OS v8.6 "Original Live Operating System" 16G USB Stick
$20.85
VINTAGE SOFTWARE | KNOPPIX STD 0.1 (SECURITY TOOLS DISTRIBUTION)
$7.57
$8.00
Knoppix Linux Bootable OS v8.6 "Original Live Operating System" 32G USB Stick
$21.42
$7.00
Knoppix 5.0.1 ULTRA RARE Linux DVD - Linux Pro Extra August 2006
$33.75