Overall impressions of this week’s macOS 10.15.3 update seem good, with relatively few problems reported, most Macs undergoing firmware update as intended, and most important of all it looks like the new build of the Mail app fixes problems with data loss, at last. Another problem which is reported to have been fixed is an issue with HP Easy Scan.

Your mileage may vary, of course, and there are some irritating effects which can mar this update for some.

If you have customised any settings which are stored in the /etc folder, which is symlinked to your Data volume, then you’ll need to check those, and possibly restore your customisations. Among those items which are likely to have been reverted to factory defaults are:

• /etc/ssh/ssh_config (if not more of the contents of that directory) is replaced in the update, so if you have customised this to provide your own defaults for ssh users, you’ll need to restore those;
• any customised /etc/sudoers file may also have been replaced;
• any modifications saved in /etc/pam.d may also have been wiped.

Although restoring previous customisations shouldn’t prove difficult, Apple failed to warn users of this behaviour. This is exactly the sort of information that an operating system vendor should declare in the release notes accompanying any update, and which Apple did in the past.

Mr. Macintosh draws attention to problems with the domain admins group in networks which bind to Active Directory: sysadmins need to verify that this group is still set for users, or those users may lose access to sudo and other admin privileges, in this article. Thankfully, this problem goes away after time, when the configuration is next refreshed.

The only odd thing which I noticed here is that Xcode’s command tools had to be reinstalled when I next opened Xcode, although no update to Xcode had been installed.

I know of one user who has attempted several full restores from Time Machine backups under 10.15.3 and has encountered many problems, including the appearance of the /AppleInternal folder which I detailed yesterday. I checked that single-item restores were working from my Time Machine backups here, and encountered no problems in restoring items from backups made before or after the 10.15.3 update was installed. I therefore don’t know whether this is confined to full restores, or whether there are other factors involved.

Thanks to Martin @martinsteiger, James and Mr. Macintosh for providing information as ever.