I'm not sure if this is a support or feature request. I have a very small test site with just a few modules installed. One of the modules (l10n_update) is installed with the very latest dev version to fix a bug in the approved version.
I wanted to run pm-update to upgrade from D7.19 to D7.20. However, I didn't particularly want to upgrade the installed modules and especially I didn't want to change the version of l10n_update.
Although I have found a --no-core parameter which allows you to upgrade only the modules, I have not found the reverse (a --core command for example). Nor does there appear to be a parameter to exclude modules (or a dialogue to update modules selectively), which I think would surely be useful.

Comments

Status:Active» Fixed

Please see --lock, described in drush help pm-update:

--lock                                 Add a persistent lock to remove the
                                           specified projects from
                                           consideration during updates.  Locks
                                           may be removed with the --unlock
                                           parameter, or overridden by
                                           specifically naming the project as a
                                           parameter to pm-update or
                                           pm-updatecode.  The lock does not
                                           affect pm-download.  See also the
                                           update-advanced project for similar
                                           and improved functionality.

Many thanks... I should have seen and understood that. I take it that "update-advanced" is now Drush Site Upgrade?

No; it is http://drupal.org/project/update_advanced. I don't know why the help says "update-advanced" instead of "update_advanced". Changed in 8.x-6.x and 7.x-5.x. Sorry for the confusion.

Status:Fixed» Closed (fixed)

Automatically closed -- issue fixed for 2 weeks with no activity.