UMSDOS HOW-TO: Installation/UN-installation and some tricks

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## 7. Installation/UN-installation and some tricks

The installation of a Umsdos is not much different from the installation of an ordinary (Ext2 based) Linux system.

There are two main differences.

## 7.1 The pseudo-root `/mnt/linux`

The normal steps for an installation are

1. Setting a partition with fdisk and formatting it.
2. Mounting it as /mnt relative to our installation root disk.
3. Copy all packages into `/mnt`.

With Umsdos, the step 1 is not required (wasn't it the goal of Umsdos not to reformat ?).

It is possible to install a Umsdos system just by copying all packages into `/mnt`. This will certainly work. But it will create a bunch of subdirectories into your DOS root directory (C:) and you won't like it. This is the reason all Umsdos installation use the pseudo-root. And this is the major difference between a normal Ext2 installation and a Umsdos one: All files are copied into `/mnt/linux`.

## 7.2 Preparing `/mnt/linux`

`/mnt/linux` is not an ordinary directory. It has to be promoted so it will correctly handle Linux long file name and special files (links, device). The step required to setup `/mnt/linux` are:

1. `mkdir /mnt/linux`
2. `umssync /mnt/linux`

That's it!

## 7.3 Making sure `/mnt/linux` is correctly setup

Even if the setup of `/mnt/linux` is pretty simple, there are many installation package out there who get it wrong. How can ?

The biggest installation problem come from an incompatible `umssync` program. Umsdos has been update in linux 1.1.88 (Can't remember exactly) and a flaw was uncovered in `umssync`. To avoid confusion in the Linux community, it was decided to raise the compatibility level required for all Umsdos tools. Old version of the tools were simply rejected.

It sounds like many distribution did not update their `umssync` utility on the installation disk.

There are still many distribution like this out there. The net result is that the directory `/mnt/linux` is not promoted at all and will truncate all long file name and will reject all special file.

It is possible to do a test very early during the installation to find out if something went wrong. Thanks to the pseudo console mechanism of Linux, you can do that without leaving the installation program. Do the following steps:

1. Press `Alt-F2` (`Alt` key at the same time as the `F2` key).
2. login as root.
3. `cd /mnt/linux` If this fail, you are trying this too early. A good time to do this is at the end of the packages selection.
4. `>TOTO`
5. `ls -l` You should see an empty file `TOTO` in uppercase. If you see it in lowercase, something went wrong. Try to do the `umssync` step again. `umssync` can be use over and over without problem. `umssync .` If there is no error message, try the `TOTO` test again. If `TOTO` appears fine, then all is OK. Something is strange in this installation, but you just save it. Continue
6. Press `Alt-F1` to get back to the installation screen.

If the test fail, the best fix is to get a newer installation root disk. You can generally fix this root disk by installing a newer version of `umssync`. This is not difficult but required a working Linux system. You simply have to mount the root disk floppy and replace the offending `umssync` with a new one.

## 7.4 Oops releasing pseudo root ...

Most Umsdos installation which fail, do this by printing this strange message. This is not a bug in Umsdos although the message looks strange. Here are the known causes.

- The most common one

  The Slackware installation try to setup a swap file very early during the installation. To do so, it asks you to select a partition (dos drive), then mount it and set the swap file.

  When installing a Slackware system, you must setup the target partition prior to install. This normally mounts the DOS partition on `/mnt`, creates the `/mnt/linux` directory and applies `umssync` on it.

  This is where most problems come from. Most user just forget the "setup target partition" step and go directly to the rest of the installation. Since `/mnt` is already mounted, this mistake goes unnotice. This means that `/mnt/linux` was not created properly (Not promoted). All special files and links and long names can't be created properly.

- Invalid umssync utility

  `/mnt/linux` was improperly setup-ed. Generally caused by an improper `umssync` utility on the installation root disk.

- Old bug in umsdos

  There was a bug in Umsdos prior to Linux 1.2.2. The pseudo-root mode would not activate properly if the file `/etc/init` was missing. `init` is now located in `/sbin`. You can fix it by getting a newer kernel. This is recommended because another bug was uncover and fixed in 1.2.2.

  If you can't upgrade, do this

  1. Boot from you installation disk.
  2. Login as root.
  3. `mount -t umsdos /dev/hdXX /mnt` where `/dev/hdXX` is your DOS partition.
  4. `cd /mnt/linux/etc`
  5. `ln -s ../sbin/init init`
  6. `cd /`
  7. `Ctrl-Alt-Del`
  8. Boot your Umsdos normally.

Unfortunatly, the first two (Installation problems) produce a completly unusable installation. Uninstall it (See next section) and install again.

## 7.5 How to UN-install a Umsdos system

One neat thing about Umsdos and its pseudo-root mechanism, is that you can UN-install it without pain. You just boot DOS and recursively delete the `linux` directory. That's all. Umsdos requires no special drivers in the config.sys, nor it creates anything special outside of the `linux` directory.

## 7.6 Moving a Umsdos system to another DOS drive

This can be done from Linux or from DOS. You just have to copy recursively the `linux` directory from one drive to the other. After that you will have to adjust you boot mechanism (generally loadlin command) and the `/etc/fstab` file.

Umsdos can live on any DOS drive. There is no need to install it on the `C:` drive, nor it is important to have it on the first hard drive. It does not matter at all.

In fact, one may decide to have several Umsdos installations on different drive just to do experiments.

## 7.7 About installing 50 Umsdos systems.

How about installing a bunch of Linux systems in no time ?

Umsdos systems are living in a DOS world. You can take advantage of this if you wish to install Linux easily.

You can install and configure a Umsdos system at your site. When you are satisfied with the configuration and the different packages you have selected, you can boot DOS and copy the complete `linux` directory to your DOS file server. Then you go to other DOS station and simply copy the files on the network drive to the local drive. That's it. Only adjust the boot script (Loadlinx) and go.

With minimal adjustment (Host name, IP number), anyone will be able to install a Linux system in a matter of minute.

Interest readers may note that installing Linux systems by copying running system also works for any other Linux systems, including Ext2 based one.

One beauty of Linux is that there is no hidden files which have to be install by magic installation program.

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