Jerome Fine replies: You forgot to say how big your ESDI drive is and which version of RT-11 you are using. If your ESDI drive is 256 MBytes or less (even up to 300 MBytes is not unreasonable) and you are using either the WQESD or at least V5.3 of RT-11, then as you note, sufficient partitions are available (maximum of 8 partitions up to V5.4G or RT-11). Note that with the standard RT-11 distribution up to V5.4G, ONLY partition ZERO is bootable since the boot code in the device driver of an RT-11 MSCP device is missing one instruction (naturally the one which takes care of the partition number - this can easily be modified in V5.4G - I have seen it in actual operation). And in general (you would need 2 active devices otherwise) the hardware boot code can do a HARDWARE BOOT of an RT-11 partition (ALWAYS partition ZERO) ONLY (there was a discussion a while back in which it was shown that with 2 active devices this can be somewhat modified) if the logical and physical UNIT numbers match. If you are using V5.5 or later, then extended device driver support is available and 64 partitions are available. In addition, starting at least with V5.6 of RT-11, NON-ZERO partitions are software bootable. Which means that you can support an 8 GBytes disk drive and simultaneously use up to 64 partitions (out of 256 on that 8 GByte drive) at one time using the partitions D00: to D77: (64 total since numbers are actually - sort of - in octal). NOTE that the standard DEC distribution allows only the first 8 partitions in the table to be bootable although it is quite possible (I have seen one version that allows ALL 64 partitions to be software bootable - actually watched D64: being booted) to re-write the boot code and have all 64 partitions bootable. Since I have probably given you too much to chew on, please respond with any questions. We all do that on occasion - in my case, more often than not. The only real difference is that with COPY/SYS you don't get a "SQUEEZEd" directory the first time through. If you have more than about 1500 files, that could be a problem. You would have to do a multiple pass since the directory would become "full". Otherwise, you can do the SQUEEZE afterwards and only the directory would be modified if there were no empty spaces. Just to be sure, I always recommend that the DU(X).SYS file being written to the device which will be booted is the device driver which is being used to perform the COPY operation. Sometimes that is not possible, but try to do so whenever you can. However, if you are using a version of RT-11 on the target bootable partition which is not compatible with the version of RT-11 that is doing the copy, that will not be possible.