How do I free disk space for an update installation?

Some 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

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.

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. Refer to the installation guide for more information on using

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. Section 5.20 of the Digital
UNIX 4.0 installation guide gives descriptions of each kernel option.

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 will not corrupt your
existing system or prevent you from performing an update, but it may
cause you to have to free space and restart the update more than once.

This bug has been fixed for Digital UNIX 4.0B.

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.
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