Our experts answer your technical questions.
Doubling Connection Speed
I have heard that it’s possible to set up Linux to combine two analog modems into one so as to double the speed of a connection. Is this true? If so, how does this work and where can I get more information on how to do this? I have Slackware 96. —Keith Bell
What you want to do is called load balancing. There is a feature you must compile into your kernel for load balancing to work and it is designed to work only with SLIP or PPP. The feature you must compile is EQL, or “Serial Line Load Balancing”. As you configure your kernel there is a small amount of help available on the option. If you look at the file /linux-source-directory/drivers/net/README.eql, you can get more information on how this works and what you need to do. Be aware that this must be supported by the other end of the connection—either another Linux box compiled with this feature or a Livingston Portmaster 2e. —Chad Robinson, BRT Technical Services Corporation firstname.lastname@example.org
I am running named as a primary DNS server. It appears to be working fine, but my /var/adm/messages file is full of lines like the following:
Dec 5 09:34:14 lancomm named: NSTATS 849796454 849648847 A=528 PTR=76 MX=96 ANY=202 Dec 5 09:34:14 lancomm named: XSTATS 849796454 849648847 RQ=902 RR=634 RIQ=0 RNXD=49 RFwdQ=393 RFwdR=562 RDupQ=5 RDupR=6 RFail=1 RFErr=0 RErr=0 RTCP=0 RAXFR=0 RLame=15 ROpts=0 SSysQ=53 SAns=509 SFwdQ=393 SFwdR=562 SDupQ=426 SFail=19 SFErr=12 SErr=1 RNotNsQ=886 SNaAns=339 SNXD=49
These messages are logged every few minutes. Are these merely extraneous debug messages, or is named misconfigured? —Bill Cunningham
They are debug messages, and don’t mean there is a configuration error. Those messages are the “extended statistics”, a compile-time option for named. If you’d like to disable this logging, simply recompile named with the XSTATS option commented out in the file:
—Bob Hauck, Wasatch Communications Group email@example.com
More Colors in X-Windows
When I run X-Windows the desktop resolution is 340X400 with 16 colors. I am wondering how to get my X server to run with a resolution of 800X600 with 256 or higher colors. I am having a hard time finding documentation or manual pages on how make this change. I am running Slackware 1.2.1 and using a Cirrus controller. —Matt Linak
Your distribution is very old. You should switch to XFree86-3.2, which includes many more supported cards. Most Cirrus controllers are supported now. Take a look at the README.Cirrus file in the XFree86 web site: www.xfree86.org . —Pierre Ficheux, Lectra Systemes firstname.lastname@example.org
Setting Up An X Terminal
I am running Linux 2.0.0 and have a second PC that I use a a terminal (serial) using a DOS term program. It’s a 486 that used to be my main machine until I upgraded. I have been trying to find information on setting it up as an X terminal, but all the HOWTO and /usr/doc files seem to focus on other things. It’s my understanding that if I put a small Linux kernel on it and use NFS for root that I should be able to do this as the machine has very limited resources these days. I know I can switch to PLIP for reasonable speed, and I have good documentation on using NFS as root, but I have not uncovered the missing information on setting it up as an X terminal. Can you direct me to a source? —Josh
Inexpensive Hardware and xdm
You do need at least some disk resources to be able to set your H86 up as an X-terminal. There are ways to do a complete net-boot on a PC, but those include obtaining a 3C509 or NE2000 Ethernet card and a boot ROM. I haven’t dealt with this method, though, because hard disks are becoming very cheap.
I recommend getting a 120MB IDE drive (you should be able to find a used one for around $25), and installing that. Then install a minimal Linux system including X, and you are set. You will need networking of some type since most Linux distributions require Ethernet for a network install. If you don’t have a CD-ROM on that box, you’ll probably want to do a network install, so pick up a cheap networking card (new NE2000 clones run about $25).
Now, for using the 486 as an X terminal, the easiest way is with xdm. You run it on your main machine, configure X on your 486, and you can then run X -query hostname on your other machine. That solution will run an X server locally, but will run all binaries off your main machine. —Donnie Barnes, Red Hat Software email@example.com
When I build a kernel (2.0.26 is the latest) with loadable module support enabled, I have troubles with the old modules compiled for 2.0.0. When I make the modules for 2.0.26, only one module is built and put under /lib/modules/2.0.26. How do I manage the other modules? When I put the 2.0.0 modules under 2.0.26, the system complains you must recompile. How do I recompile them? —Ivo Naninck
Patch or Scratch?
You did not mention whether you have applied a patch or installed a linux-2.0.26.tar.gz. If you have installed from scratch, don’t forget to run make menuconfig, in order to select which features you want as modules. If you have applied a patch, use:
make dep make clean make zImage<\n> make modules make modules_install
I would prefer using make zlilo rather than make zImage, but the latter would work. This should compile your kernel and all the modules you have specified. Once the kernel is installed, you should be able to take care of dependencies with the command depmod -a the next time you boot. —Mario de Mello Bittencourt NetoWebSlave System Administrator
Making Rescue Disks
I am wondering if there is a guide on how to make a rescue disk that includes my choice of kernel and root, including some basic tools to help me restore my box in case of an accident. —Eskinder Mesfin
The Linux Bootdisk HOWTO by Graham Chapman (firstname.lastname@example.org) describes how to create maintenance disks. The text is available at http://sunsite.unc.edu/LDP/HOWTO and ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO. —Martin Michlmayer email@example.com
Linux Won’t Accept Mask
We have a complex 10B2 network with 4 subnets. We recently got connected to the Internet with ISDN and a Pipeline 50 and were given a single class C address. We have created a subnet scheme for assigning IPs to all of our WFW3.11, Win95, and WinNT computers. When we tried to set up the Linux box as an HTTP and ftp server, we were unable to get the Linux software to accept 255.255.255.224 as the subnet mask. Will Linux do subnets this way? —Richard C. Guglomo
Linux And Subnets
Linux does do subnets, and 224 is a valid mask. Valid masks must have contiguous high bits set and 224 is 1110 0000 in binary. In theory this should work, but there are some pitfalls.
It could be that the IP you are assigning to the interface isn’t on a valid 224 subnet. With that mask your network addresses will be 5 bits. In other words, subnets will fall on multiples of 32 (decimal)—0, 32, 64. Those IP addresses are “network addresses” and can’t be used for an interface. Similarly, the “all ones” addresses are reserved for broadcast—that would be 31, 63, and so on in this case.
You cannot assign a network address as the IP for a specific interface. So, you can’t use something like 192.168.1.32 as the interface address. Instead you should use 33-62 for the devices on the 32 subnet (63 would be the broadcast address and is also reserved), 65-95 for the 62 subnet, and so on. —Bob Hauck, Wasatch Communications Group firstname.lastname@example.org
Can’t Disable LILO
I have installed Red Hat, and I now want the option of running another OS on my machine, but I have not been able to disable LILO. I have installed DOS, but when the machine re-boots, I get LILO, and when I press TAB, I have no other options. I have fdisked the hard drive through both the Red Hat install program and DOS without any luck. I wanted to move the LILO from the mbr but have not been able to do this. —Josef Davis
Adding DOS option to LILO
You can replace LILO with the DOS boot loader by issuing the DOS command fdisk /mbr. In your case, however, the solution is to add DOS as an option to LILO. You can do this by adding the following directive at the end of the LILO configuration file, /etc/lilo.conf:
other = /dev/sda4 label = DOS table = /dev/sda
You have to replace the value of other with the device of your DOS partition; the same applies to table where you have to insert the device of your hard disk (/dev/hda in the case of the first IDE hard disk).
After inserting these lines you have to refresh the boot record by issuing /sbin/lilo as root. When booting your machine the next time, you will have the option DOS within LILO. —Martin Michlmayer email@example.com