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Home is not etcetera
OR
Configs in $HOME don’t necessarily have the same names as those in /etc.

Goal: SSH into remote using alias hks.

Problem:

• ssh hks returned "ssh: Could not resolve hostname hks: Name or service not known".
• At another point, the connection attempt returned "No route to host.".

Tests:

• ssh -G hks showed which settings SSH was applying to the alias.
• ssh -G hks -F /etc/ssh/ssh_config tested that specific config file.
• ls -l and namei -l checked the config file’s ownership, permissions, and directory access.

Solution and reason: The alias was in ~/.ssh/ssh_config, but the standard per-user config is ~/.ssh/config.
Permissions set to 600 avoided SSH errors after the file was copied from backup. The system-wide /etc/ssh/ssh_config should be root:root but readable by all (so 644).
“No route to host” is o.c. a network-reachability issue, eg. when a damn laptop goes sleepin' even when plugged :-o

SSH needs a proper ssh_config - even empty values in a non affected host block access to target

Goal: Find missconfigurations and check perms on /etc/ssh/ssh_config.

Problem: ls -l /etc/ssh/ssh_config showed:

-rw------- 1 644 root 8307 Oct 13 03:04 /etc/ssh/ssh_config

We mistook 644 for the file’s permissions, but 644 was actually the file’s owner :-o

Test: stat /etc/ssh/ssh_config made the permissions easier to differentiate from owner:group next to it: Access: (0600/-rw-------).

Solution and reason:
A) We had run chown 644 instead of chmod 644 :-o
B) Despite NOT loggin in to "OtherHost" its empty values blocked ANY target access:

Host            OtherHost
  User              
  HostName         

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