Harden system configurations

Apply the approved CIS kernel and SSH hardening settings to the staging fleet: disable root login over SSH, set PermitRootLogin no, enforce SSH protocol 2, and apply the kernel sysctl values from the hardening spec; reboot two test nodes, verify services start, then roll to the rest tomorrow morning.

Before I push the hardening baseline, make it easy for reviewers: list the exact SSH and kernel settings that change, show which services might be affected, provide a rollback command for each change, and call out any compatibility risks for the Java app team so a reviewer can sign off quickly.

I set PermitRootLogin no on a test host and immediately lost automated connections from the backup agent, which uses a key tied to root. I don't know if changing the key or modifying the agent is safer for production. What is the likely safer path and the minimal immediate fix to restore backups while keeping hardening progress?

Every time we try to enforce baseline hardening, an application breaks and the change is rolled back, so we never make progress. Where are we most likely losing momentum: lack of a compatibility test harness, absence of owner sign-off per app, or rushing config changes without a canary? Recommend one habit to introduce that will let us harden steadily and one quick way to enforce it for the next three changes.