If you should be so unfortunate as to lose or corrupt the OS2.INI file, you will want to restore it from the most recent, clean, backup copy you have. This will normally be the one that was copied when you last booted the system.
Since OS2.INI is kept open at all times by the Workplace Shell, you cannot simply copy the backup over the current file. The two approaches to resolving this are outlined below.
Reboot from Diskette
This procedure will only recover your system to the point at which it was previously saved. Any objects and folders that you added since that point will be lost, as will any colors and desktop settings which you altered.
Booting from diskette to restore the OS2.INI file requires the following steps:
COPY A:\*.INI C:\OS2
System Install from Alt-F1
The Alt-F1 keystroke combination, described in Critical System Files will copy the CONFIG.SYS, OS2.INI and OS2SYS.INI files from the OS2\INSTALL directory into the appropriate directories before reading those files. A fuller discussion of this technique may be found in OS/2 Version 2.0 - Volume 1: Control Program.
What is the Effect of Restoring a Back-level OS2.INI?
If you have to restore an old OS2.INI to an otherwise intact system, there may be conflicts between the contents of OS2.INI and the files, directories and EAs on the disks. The relationships between these are discussed more fully in Workplace Shell Implementation.
The degree of problems caused will depend on how many program files have been copied and how many shadow copies have been made since the date that the OS2.INI file was copied. This is because these objects are stored in the OS2.INI file and so will be lost when it is replaced.
The usual problem that ensues is that a folder will have a pointer to that program or copy in its directory EA, but now the pointer no longer exists. The solution is easy; perform a refresh on the folder, then copy the program or file shadow again.