Linux Server
Find a Linux daemon listening only on loopback
A service can work from localhost while every remote client fails because its listener binds to the wrong address.
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Matching articles (100)
Clear filtersLinux Server
Validate NGINX configuration before a planned reload
An NGINX reload can fail because a referenced file, certificate or directive is invalid. Test the same installed configuration first.
Read article : Validate NGINX configuration before a planned reloadLinux Server
Check Apache configuration with the correct distribution wrapper
An Apache deployment can fail before it serves traffic because of configuration or module errors. Use the installed distro's supported wrapper.
Read article : Check Apache configuration with the correct distribution wrapperLinux Server
Separate an NGINX 502 from a failing backend
A proxy can be healthy while its upstream is down, misaddressed or using a different protocol. Test the intended local backend without client credentials.
Read article : Separate an NGINX 502 from a failing backendLinux Server
Inspect the certificate file a Linux service is configured to load
A renewed certificate on disk may not be the one a daemon serves, or the file may have the wrong name or validity window.
Read article : Inspect the certificate file a Linux service is configured to loadLinux Server
Investigate an HTTP redirect loop through proxy and origin evidence
A site can loop when the application misinterprets forwarded scheme or hostname information. Inspect one response before following an unlimited chain.
Read article : Investigate an HTTP redirect loop through proxy and origin evidenceLinux Server
Inspect nftables rules before assuming the Linux firewall is open
A service can listen correctly while an effective ruleset drops its traffic. Read the actual rules and counters in the right namespace.
Read article : Inspect nftables rules before assuming the Linux firewall is openLinux Server
Find the firewalld zone actually assigned to a server interface
Opening a port in the wrong zone can leave the intended service blocked. Inspect active zone assignments first.
Read article : Find the firewalld zone actually assigned to a server interfaceLinux Server
Read Ubuntu UFW policy before adding another server rule
An application can remain blocked because a rule's direction, source or order differs from the intended access path.
Read article : Read Ubuntu UFW policy before adding another server ruleLinux Server
Validate OpenSSH server configuration before a remote-access change
A syntax or key-path error can prevent the next SSH restart and lock out administrators. Test configuration before touching the running service.
Read article : Validate OpenSSH server configuration before a remote-access changeLinux Server
Check path traversal and ownership during SSH public-key rejection
A valid public key can be ignored when ownership or permissions along the account's path violate the server's access rules.
Read article : Check path traversal and ownership during SSH public-key rejectionLinux Server
Check interface MTU when a server works for small requests only
A tunnel or overlay path can fail for larger packets while basic reachability works. Record the interface's actual MTU and path context.
Read article : Check interface MTU when a server works for small requests onlyStart with the foundations
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