Important Information Regarding Digital UNIX
Update Installation Disk Space Problems
A number of users have experienced problems recovering ample disk
space after an update installation has aborted due to insufficient
space. The following is an example of a typical problem encountered
during an update:
1) The update installation exits and indicates that additional space is
needed in a particular file system (root, /usr, and/or /var) to perform
the update.
2) The user deletes or moves files from the affected file system
and/or removes subsets.
3) The user initiates another update attempt.
4) The update installation aborts again because of lack of space, even
though the user believes that the space requested during the first
attempt has been recovered.
There may be several reasons for this problem:
o Some users are not following the proper method for removing
system files to recover disk space, as described below.
o A bug has been identified in the update installation disk
space calculation for AdvFS file systems. See "AdvFS Disk Space
Calculation Bug" below.
o Deletion of small files from an AdvFS file system may not
immediately free additional space. See "Additional AdvFS
Considerations" below.
How to Properly Free Disk Space for an Update Installation
----------------------------------------------------------
The proper methods for freeing disk space are as follows:
1) Remove any non-critical optional subsets using 'setld -d'.
Deleting or moving individual system files without using the
'setld' command will not yield the additional space needed to
continue.
Refer to the appropriate appendix of the Installation Guide
containing the subset size information that corresponds to the
version of Digital UNIX that you have currently installed to
help you decide which subsets to remove.
2) Remove any non-critical user-added files which are not part of
the base or layered product inventory. Typical large space
consumers are left over core files and kernels that are no
longer required.
3) For those who have previously performed Digital UNIX update
installations, left over obsolete system files, .PreUPD files,
and .PreMRG files can use significant amounts of file system
space.
Use the 'updadmin' utility to first back-up then delete these
files.
4) For AdvFS filesystems, it is possible to save approximately
3MB in root by building a mandatory only kernel (the default)
rather than an interactive kernel (i.e. do not specify the "-i"
flag to installupdate). Note that you must specify the "-i"
flag if there are optional kernel selections that your system
depends upon that cannot be satisfied by a mandatory kernel.
Why doesn't deleting individual system files free space for the update? -----------------------------------------------------------------------
Deleting files which are part of installed base or layered
product subsets will not produce additional free space because the
update installation takes into account that these old files will be
replaced by new versions. The disk space calculation determines how
much additional space is needed to replace an old version of a file
with its new version.
If the old version of a file is removed without removing the
entire subset in which it resides, the update installation will still
put the new version on the system. In this situation the full size
of the new file will be allocated instead of the difference between the
size of the original and new versions.
For example, if /genvmunix was 7MB and a new version of
/genvmunix was 8MB, update would need to reserve 1MB of free space
for the new version. If /genvmunix was deleted before the update,
the disk space calculation would then reserve the full 8MB for the
new file. So although 7MB was freed before the update, 7MB more
would be reserved during the update, which would result in no
difference in the amount of additional space needed to continue the
update.
AdvFS Disk Space Calculation Bug
--------------------------------
There is currently a known problem with the update space
calculation procedure for AdvFS file systems. The bug may cause the
update installation to report an amount of 'additional space needed'
that is smaller than what is actually necessary. Therefore subsequent
update attempts may still request additional space even after the amount
originally requested has been freed. This bug has been fixed for future
releases.
Additional AdvFS File System Considerations
-------------------------------------------
When removing small files (less than 8K) from an AdvFS file
system, additional free space may not be made available to the file
system immediately. After the total amount of space consumed by these
deleted files reaches a threshold value, all of the space is made
available in one large block. This explains why deletion of several
small files may not increase the available block count (as shown by
"df", for example). In this case the user must continue to delete
non-system user-added files until there is an adequate increase in the
available block count to allow the update installation to continue.
-----------------------------------------------------------------------
Brad Musolff bdm_at_unx.dec.com
Digital Equipment Corporation
200 Route 9 North
Manalapan, NJ 07726-9455
Received on Fri Sep 06 1996 - 22:27:57 NZST