0.0 Edit History.

5 September 1998: Begin FAQ. This FAQ will be sparse for several months.
4 October 1998: Document various problems.

1.0 What is the DCOM for Linux FAQ?

The DCOM for Linux FAQ is a list of frequently asked questions about installing, developing and administering DCOM on Linux computers. Software AG's EntireX DCOM FAQ is a prerequsite to this document.

1.1 Where is the home site for the DCOM for Linux FAQ?

The home site for the DCOM for Linux FAQ is http://SoftworksLtd.com/dcomlinuxfaq.html. The maintainer is Bob Salita of Softworks Limited, a software developer heavily entangled in DCOM for UNIX projects.

1.2 What is DCOM?

DCOM is a distributed object technology developed by Microsoft. In simple programmer terms, DCOM provides a mechanism for transparently executing function calls across computer systems. DCOM is a complex body of software that incorporates technologies such as distributed objects programming, object life cycle management, communications protocols, security, cross-platform interoperability. DCOM is in the same solution space as CORBA. DCOM is fully implemented on Windows NT and almost fully featured on Windows 95 and Windows 98.

For an example of what DCOM for UNIX can make possible, check out this Visual Basic source code that wraps the Linux  libc shared object into a class library. It is running on Linux using DCOM and an unreleased beta of software from the VBVM project.

1.3 Who are the players in DCOM?

Microsoft developed DCOM for use on Windows. About 1996, Microsoft licensed DCOM technology to other organizations including Compaq (Digitial Equipment), HP, Mainsoft, Open Group, and Software AG. Software AG deserves credit for performing the majority of DCOM porting to UNIX and OS/390 mainframes. Software AG maintains the largest staff of DCOM for UNIX personel. Microsoft has released ports for Sun, HP/UX and is working on a 64-bit port to the Dec Alpha.

1.4 What ports of DCOM are available and who is the vendor?

• *BSD - nobody
• DEC (Compaq) Alpha 64-bit - Software AG (Microsoft is working on a port).
• HP - Mainsoft, HP, Microsoft, Software AG
• IBM AIX - Software AG
• IBM OS/390 - Software AG
• Linux - Software AG
• SCO - nobody
• SGI - Mainsoft
• Sun Solaris - Microsoft, Software AG

No. I don't think there is a need at present. Some proposed names are [alt|comp].os.unix.programmer.com or if Microsoft supported a group - microsoft.public.unix.dcom?

1.6 Is there an email discussion list for DCOM for Linux/UNIX?

There is an email discussion list for DCOM for UNIX called dcomunix.

1.7 Should I get involved in DCOM for Linux/UNIX?

DCOM for Linux has been released by Software AG but without support. So production use is out of the question. However, it works pretty well for purposes of evaluating the technology and developing proof of concept programs. DCOM for UNIX won't hit full stride for several years but its feasible to start the evaluation process now. More maturity and a killer app is needed for widespread acceptance. My guess is that distributed computing will get a kick start when Netscape releases a CORBA enabled version of Navigator. That will peak interest.

2.0 Where can I get DCOM for Linux?

DCOM for Linux runtime, SDK, examples and documentation are available for free from Software AG. However, Software AG doesn't provide any support for DCOM for Linux, neither for free nor for pay. Your best chance for support is from the dcomunix email discussion list mentioned above.

2.1 What are DCOM for Linux runtime software requirements?

From Software AG's Linux runtime documentation:

• Linux kernel 2.0.30+ (available from ftp.funet.fi and mirror sites)
• GNU libc 5.4.38+ (available from tsx-11.mit.edu and mirror sites)
• GNU ld.so 1.9.5+ (same as above)
• linuxthreads 0.5 exactly (but my experience shows 0.71+ is best) (http://pauillac.inria.fr/~xleroy/linuxthreads)

From Software AG's Linux SDK documentation:

• GNU gcc compiler 2.7.2.3+ (available from tsx-11.mit.edu and mirrors)
• GNU C++ library 2.7.2.8 (same location)
• GNU binary utilities 2.8.1.0.15 (same location)

No distribution contains all of the required software packages. However, SuSE Linux 5.2 almost meets the minimum requirements. DCOM for Linux on SuSE Linux 5.3 seems to have worked on one in-house system but not on another. You only need to install an update of the linuxthreads package. Although 5.2 and 5.3 contain GNU software that's slightly older than SDK requirements, I haven't experienced any problems with GNU stuff, but I program in C, not C++. Your mileage may vary.

Alas, DCOM for Linux does not work with distributions based on glibc 2.x such as RedHat. According to Software AG, this is because of bugs in glibc 2.x.

3.0 Installing DCOM for Linux

Installing DCOM for Linux is somewhat difficult for newbies. Generally the documentation is pretty good. For me, the most difficult part was understanding how to modify the dcomconfig file. So here's a diff that might help. Two lines were edited. In place of "yournode.yourdomain.com" use the ip address of your primary NT server. My NT server has an IP number of "207.227.199.79". Modify the other line as follows, replace "yourdomain" with the name or your NT server domain. If your NT system is a standalone server, then use the first name that shows up when you do a "net name" command on the primary NT server.

113c113
< +COOL_PAULA_DC_ADDRESS=yournode.yourdomain.com
---
> +COOL_PAULA_DC_ADDRESS=207.227.199.94
126c126
< +COOL_PRIMARY_DOMAIN=yourdomain
---
> +COOL_PRIMARY_DOMAIN=NT_SERVER

4.0 Bugs in DCOM for Linux

Before assuming there is a bug in DCOM for Linux, double check conformance with all of the software requirements mentioned above. Here are some reported bugs:

• midl terminates with a signal 11 but seems to complete its work.
• problem with vtable for class that contains a property get???
• "ntwopper ntd" occasionally fails after reboot. Executing a second time usually succeeds.
• sserver demo program located in $DCOBIN/DCOverify fails after 4 invocations on Linux.
• Occasional error: "ntd: queue.h:29: enqueue: Assertion `th->p_nextwaiting == ((void *)0)0)
• When DCOM hangs, a "ps x" command shows too many DCOM related processes. Some processes are marked as zombied. "sermon shutdown" hangs too.

• Many error numbers are undocumented. This is a major weakness in DCOM for UNIX packages.
• 800706B?: Errors are security releated. Check that paulad is running on Linux. Check that paulas.exe is running on NT. Does dcomconfig have the correct IP address and domain name? Does your Linux system support DCOM for Linux? Is your system IP address and hostname correct? I had to use the system admin tool (YaST for SuSE distributions) to make IP address and hostname changes because manual changes to /etc/rc.config caused this kind of error.
• ServiceMain failed 00000014: Registry related error. When I get this message, only a reboot seems to fix it. If it persists, your registry may be corrupt. Restore a backup. The registry files are located in $DCODIR/$DCOVERS/reg.

There aren't any published benchmarks. DCOM performance under Linux seems to be pretty good considering the added overhead of remoting objects. Certainly fast enough to solve a wide range of problems suited to distributed objects technology. I hope to post benchmarks by the end of October.