Best of Technical Support

Our experts answer your technical questions.
Multithread Applications

Which library do I need to use for multithread applications? I found pthread.h in /usr/include/, but I didn't find libthread.a in /usr/lib/ as I can in AIX. —Ju Rao Slackware

There is an excellent threads library available called LinuxThreads. You can download the latest version from [For more information on LinuxThreads, see] —Chad Robinson

Missing svgalib

Hi, I am a new user, and I have what I am sure is a simple question. I upgraded the kernel from version 1.2. Now when I run games, I get an error about a missing svgalib. Consequently, I cannot get any picture. I am using an ATI 3D Expression with 2MB. How do I edit the config or lib file in order to indicate which libraries I have? —Jonathan Barrie Slackware

I'll bet you upgraded the libraries as well as the kernel. Nowadays, everything uses shared libraries, and programs can't run unless the right shared libraries are installed.

I'd try ldd <program> to check which libraries it finds and which it doesn't. Once you know which libraries are missing, you can then install the Slackware packages that provide them.

You can also run ldconfig -v to see which libraries are installed; if your program looks for a different version of a library already installed, look for “backward compatibility” packages.

Note that newer distributions trace dependencies between packets, so you are unlikely to experience this error when using them. —Alessandro Rubini

Customizing Login Screens

How do I customize the “Login” screens for TELNET and FTP logins? —Robert Farrell

For TELNET, create and edit the /etc/ file with whatever you wish to be displayed for the login screen. You can also edit the /etc/motd file to display the message of the day after someone logs in.

For FTP, go to the root directory of the FTP space (usually /home/ftp/). You can verify the location and file names by looking in /etc/ftpaccess. Edit the welcome.msg file to whatever you wish to be displayed. If you want specific messages to be displayed when users enter into a particular directory, edit the .message file in that directory. —Mark Bishop

Backup Scheme

In a 50/50-mixed NT/Linux LAN of four to six servers, what is the best tape backup scheme you recommend? Where should I install the backup units—on the NT or Linux or both? What tape backup utilities should I use? What if Solaris 2.5 servers are added? —Jon ChunRed Hat

tar has always been the standard backup tool in the UNIX environment. If you want something more powerful, you should investigate cpio or afio, both of which are standard, command-line tools. BRU and other commercial backup facilities exist as well.

If you want to back up mixed NT and UNIX systems, you will most likely need to use a dedicated backup facility for the NT servers. A backup of NT is nice but backing up your domain server won't be very useful unless you include the registry settings, which only an NT backup tool can do.

The best possible solution is to install a tape drive in each server and use that server's own tools (NTBackup on NT, tar on UNIX) to back it up. That method will provide you with the fastest recovery times as you won't be restoring across the LAN.

If you don't need to cut costs, you can investigate ARCServe or another commercial backup utility. These tools include clients for many platforms, and you can probably get the SCO client working under Linux using iBCS2. That would allow you to use a Windows NT machine to back up your UNIX servers. —Chad Robinson

You can use the SMBFS functionality of the Linux kernel in order to mount remote NT servers on your Linux system:

smbmount //NT_SERVER//FOO /nt_server

Then you can save these directories with tar or any other backup utility.

A more efficient solution (but not free) is to use commercial software such as ARKEIA or BRU which support remote NT/95 system backups. —Pierre Ficheux, Lectra Systèmes

Using a Teles Card

I have a Teles ISDN card, which I would like to use under Linux. After looking around a bit I found a driver in the Red Hat distribution. So, I compiled a new kernel with support for the Teles card. However, I have no idea how to use it. With a standard modem I can talk with at commands to /dev/modem/, but how does it work with the ISDN card? —Rien Broekstra Red Hat

You need the isdn4k-utils. There are other packages, e.g., vbox for building an answering machine, but this is basic. Check or read /usr/src/linux/Documentation/isdn/* for locations of additional packages. —Ralf W. Stephan

I'm fairly certain that you didn't need to recompile your kernel. The Red Hat kernel packages build ISDN support as modules. (I'm sure they do as of 5.0, and I think we did in 4.2 as well.)

Anyway, the best place to find this type of information is in /usr/src/linux/Documentation/isdn/README.HiSax/. Everything you need should be covered there. —Donnie Barnes


Geek Guide
The DevOps Toolbox

Tools and Technologies for Scale and Reliability
by Linux Journal Editor Bill Childers

Get your free copy today

Sponsored by IBM

Upcoming Webinar
8 Signs You're Beyond Cron

Scheduling Crontabs With an Enterprise Scheduler
11am CDT, April 29th
Moderated by Linux Journal Contributor Mike Diehl

Sign up now

Sponsored by Skybot