Vodacom Modem Driver

Good Day, Sir: I'm very new to the Linux platform, coming from "Windoze," not realising really how unique a person can make his own Linux. Being new to the Linux platform gave me loads of entertainment so far, but now I've hit a brick wall.

At home, I'm running CentOS. On my work laptop I'm running it through Oracle and have been able to keep it fully updated, but at home I don't have ADSL or WiFi; I use a USB modem from Vodacom and a South African service provider that supplies me with Internet.

Now here is the issue: On my Windows PC it works perfectly, but when I plug it in to my spare Linux PC at home, my modem doesn't detect or allow me to install. The modem model is a K3772-Z. I have searched all over the Internet for drivers that will allow me to install it. Can you please assist in helping me with a solution?

Thanks a lot if you can help me.

Groete/Regards, Jaco

Answer: Many modems identify themselves to Linux as a "serial device" (or serial terminal); these can be used with desktop software like KPPP or the modem part of network manager using the standard "AT" protocol and PPP for dialup. However, some other modems require special drivers to even operate as modems, and in some cases, these drives are only provided for one or the other Windows version. Your modem seems to be one of those that incorrectly identify itself as a CD-ROM (allowing a Windows driver installation, then resetting itself to become a serial device) or (incorrectly) wired network device. The package and command usb_modeswitch, available for many Linux distributions can take care of switching the device back to serial mode: However, it does not work for every case.

I found a how-to for fixing the modem under Ubuntu [1], but it requires some administrative commands. The command reported as working for a Huawei E220 HSDPA Modem is:

sudo usb_modeswitch -v 0x12d1 -p 0x1003 -V 0x12d1 -P 1003 -R

The numbers 0x12d1 and 1003 are taken from the output of command lsusb, where your modem should be listed; they are the modem's vendor and device ID.

Another option could be:

sudo ifconfig usb0 -arp

which can change the mode of a USB modem+network device just by disabling the ARP protocol.

Sudo will ask for the root password on Ubuntu. If you add one or both of these lines to a startup file like /etc/rc.local, they will be called as root automatically, and the "sudo" can be left out.

Time Issues: Linux vs. Windows

I noticed that the time displayed on a dual-boot machine differs between Knoppix/Linux and Windows. Is there a way to synchronize both?

Answer: A Desktop PC or Notebook has two clocks: the built-in real-time (or "BIOS") clock, which is read during boot, and the system time, which is used during normal operation.

Although it is common under Unix/Linux always to leave the BIOS/real-time clock in Universal time (UTC) and let the system time be set by time zone settings automatically during boot, under Windows, it seems to be common instead to have the real-time clock in "local time" and even rewrite the real-time clocks time during the daylight savings time switch. It is possible for both operating systems to change the default "BIOS" time interpretation to either "localtime" or UTC; however, it's probably easier to do this under Linux than search for an appropriate setting or registry patch in Windows.

When Knoppix reads the time from the real-time clock, it honors the file /etc/adjtime, which contains UTC in the last line, if the BIOS time is expected in universal time, or LOCAL, if the BIOS time is "local time" (or rather "local time difference from UTC").

Changing this file will change Linux behavior when reading the real-time clock with hwclock -s during system start.

However, a GNU/Linux system will not write back its own system time to the BIOS automatically unless instructed to do so during system shutdown, whereas Windows will do this frequently, so you might still experience differences when switching to and from daylight savings time.