Introduction to Ext-OS/2

# Read-Write Access to Linux Partitions Under OS/2

by Larry Ayers <layers@vax2.rain.gen.mo.us>
Copyright (c) 1996

##### Published in Issue of the Linux Gazette

## Introduction

Matthieu Willm, a German IBM employee, has been creating (in his spare time) an ext2 filesystem driver for OS/2. It has been through several beta levels now and seems stable and usable. Of course it would be wise to have your backups all up-to-date before installing a package which modifies the way your OS interprets the disk partition table!

### Contents

The ext-os2 software is distributed as a zipped archive which contains ample documentation, both in HTML format and in IBM's .inf format.

An integral part of the package is a partition filter written by Deon van der Westhuysen. This filter is loaded at bootup (via a config.sys entry) and lets OS/2 assign drive letters to ext2 partitions. A switch can follow the config.sys entry which will enable read-write access; the default is read-only.

Willm's filesystem driver is also loaded at boot-up. It's a strange sensation to start up a filemanager under OS/2 and see several new drive-letters included. Each Linux type 83 partition is assigned a drive-letter beyond your present OS/2 and DOS partitions.

As an example, my system's main linux partition becomes H:, and /usr/X11R6 becomes G:, and is not accessible from H:/X11R6. Symbolic links and directory mountings are ignored.

### Installation

The docs say you can install the package using the "Device Driver Install" program, but for some reason this hasn't worked for me. The alternate manual installation method, which consists of editing the config.sys file, worked well, though.

Since I don't always need to access Linux partitions, I did my config.sys modifications to a copy named "config.l", in the \os2\boot directory, and added a line (L: Linux access) to the altf1.bot file in the same directory. This presents me with the choice of booting either with ext2 enabled or with it disabled.

### The Monitor Utility

A PM notebook-style program is included which allows you to see how large the dynamic cache has become, as well as a view of messages from the ifs itself.

Click on these links to see screen shots of the monitor.

Page One: Ext-OS/2 Monitor
Page Two: Ext-OS/2 Monitor
Page Three: Ext-OS/2 Monitor

### Caveats

Installation of Ext-OS/2 does increase OS/2's memory usage, depending on how much memory you allocate in config.sys for the dynamic cache (the default and minimum is 245 kb.). All in all you can expect about a 300-400 kb. memory hit. A small, invisible program called ext_lw.exe is started from the config.sys; its purpose is to continually attempt to shrink the amount of memory used for dynamic cache. Its efforts are visible in the monitor notebook.

One thing to watch for, say if you should have an irrestible urge to edit your .fvwmrc file while in an OS/2 session, is that your file will be saved with the extra carriage-return (^M) at the end of every line, and your file probably won't work! Either use one of those ubiquitous dos-to-unix utilities on the file after editing it, or use an OS/2 editor that knows how to write a unix text file (like FTE).

By default, every time you boot back to Linux a filesystem check is forced, which increases boot time by a few seconds. This can be disabled, but I wouldn't recommend it.

Remember to back everything up first! This program has worked remarkably well for me, but YMMV!

### Where To Get It

The current (as of 28 Jan 1996) Ext-OS/2 package is available via ftp from:

hobbes.nmsu.edu

ftp.cc.gatech.edu

ftp.leo.org

Back up to the Linux Gazette!