"The connection to service named com.apple.lsd.modifydb was invalidated"

Back to the etrecheck report:

Configuration Files:

File /etc/sysctl.conf exists but not expected

  /etc/hosts - Count: 40

The hosts file has been modified. This "may" be the result of some malware modifying it in order to prevent security updates, or redirecting you to some advertiser's web page instead of where you wanted to go.

The added sysctl.conf may be from malware, too.

Thanks for helping out Greg! I checked out the /etc/sysctl.conf file and it belongs to the TunnelBlick app which is a free VPN creator app. When I double clicked it, it comes up with a warning message from the app basically saying that the VPN configuration you are trying to install may take control of your computer and do you still wish to install it. So I think it’s a safe file. Just in case, I removed it and the app still worked okay so I put it back since I think it’s an important warning mechanism. As far as the hosts file goes, everything in there all seems to check out as i recognize them all, except for the last entry:

# 74.208.10.249 gs.apple.com

Not sure where it came from or what I should do with it....

but as I mentioned before, when I try the 10.13.6 update, it downloads the entire thing through the software updater, asks to do the reboot, does the reboot, comes back up fine, but when I check, it still says the 10.13.6 update is available! I tried it again tonight and still no go...

Ok I think I understand now! I clicked on the box to uncheck the Keychain, then told it to Keep on the Mac, then rebooted, but the ‘secd’ was still there for about five minutes again when it came back up. So turning off iCloud altogether solved the Safaribookmarkssyncagent issue, but turning off Keychain didn’t help with ‘secd’. :/

Oh and when I rebooted, my Time Machine disappeared from my desktop again!

"checked out as I recognize them all"....

The hosts file has priority over normal DNS server access to web addresses. Having it listed in the hosts file to me means:

1) you put the entry in there because you want to refer to some site that isn't normally found in a DNS server. or 2) some malware is actually directing your browser to the wrong sites.

Example - I have in the past put entries in the host file because I wanted to connect to computers in my own network by name instead of IP address.

Most of us don't need more than the standard 10 lines in the hosts file. I don't use a VPN, so that may be the difference -- I'm just checking.

I see that link refers to Cydia, but no my iPhone is not jailbroken. Lol

Ive noticed other posts with references to it, some people seem to have it, some don’t, others with a slightly different IP address in front of it. Do you guys have it in your hosts file? It shouldn’t actually be doing anything anyways in mine since it has the # in front of it, correct?

Ill delete it anyways and reboot and see if it makes any difference...

My hosts file is 1,234 lines long, 34.2K, & does not Have it.

I believe the original one was...

##

# Host Database

#

# localhost is used to configure the loopback interface

# when the system is booting. Do not change this entry.

##

127.0.0.1 localhost

255.255.255.255 broadcasthost

::1 localhost

fe80::1%lo0 localhost

Correct, the # in front should make it a comment.

How hot is it where you are... yesterday my iMac froze & couldn't restart, external drives were like frying hot, let everything cool with extra box fan going, triedc starting & had symptoms much the same as yours, I suspected Video card went out due to heat.. it's a weak point with Apple's Laptops & iMacs.

After more cooling the iMac started in Safe Mode but with video anomalies, got MacFansControl running, yikes... Ambient temp was 108° F., CPU & GPU were in high 160° F., was only 86° F. outside?

It's cooler today & repair drives right now.

Safe Boot from the HD, (holding Shift key down at bootup), does the problem occur in Safe Mode?

Yes, likely in Login Items, Launch Daemons, or Launch Agents.

Well, with a TM backup I'd think you could restore Keychains if it did trash them, updating my TM backup to give a try to turning it on then off.

Why not hit the "Keep on This Mac" button?

No, sorry for any confusion, we just want to stop iCloud from doing whatever with secd... I believe that might be the problem, restart after hitting the ‘Keep on this Mac’ & pausing a minute.