Required allow rules are already in /etc/hosts.allow.
Deny all other clients for TCP Wrappers-aware daemons in /etc/hosts.deny.
Which line is appropriate?
ALL : ALL in hosts.deny provides a default deny for requests not already permitted by hosts.allow.
Detailed explanation
ALL : ALLCorrect. It matches every daemon and client as the fallback deny rule.
Correct. It matches every daemon and client as the fallback deny rule.
ALLOW : ALLIncorrect. ALLOW is not the token for all daemons.
Incorrect. ALLOW is not the token for all daemons.
ALL = DENYIncorrect. It does not use daemon:client syntax.
Incorrect. It does not use daemon:client syntax.
DENY ALL FROM ALLIncorrect. This is not the standard hosts.deny rule format.
Incorrect. This is not the standard hosts.deny rule format.
Try it yourself
An example you can run in a temporary verification environment.
printf '%s
' 'ALL : ALL'Expected result
ALL : ALLKey points
- ALL daemons
- ALL clients
- Design allow rules first
Notes
- Environment: hosts_access rule構文の表示のみ
- Command output formatting can vary slightly by distribution or tool version.
- Run the example in a temporary directory or process when possible.
Foundation review
Read the scope first
Check whether the command acts on the current shell, a new process, an existing process, or a file.
Verify the observable result
Use the supplied command and compare the output with the expected result.