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That option would inspect `systemctl list-sockets`, service and socket unit states, live listeners and a controlled remote connection attempt, but it addresses a different concern. SSH server host keys identify the remote server and protect against impersonation; host keys are different from user public-key authentication keys.

This alternative addresses Sudoers least privilege and safe editing, not the specific issue of SSH server host keys and client trust decisions: Grant narrowly scoped sudo privileges using visudo or a validated sudoers.d fragment, then test as the intended identity.

This shortcut is unsafe for the present Linux issue: Disable strict host-key checking permanently and copy one VM image's SSH host private keys unchanged to every clone. SSH server host keys identify the remote server and protect against impersonation; host keys are different from user public-key authentication keys.

This alternative addresses Shadow password file permissions and hash protection, not the specific issue of SSH user keys, authorized_keys and agent handling: Restore restricted shadow database ownership and permissions using distribution-supported account tools and protect password hashes from general reads. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

That option would verify host-key fingerprints through a trusted channel and provision distinct server host keys for each machine, updating client trust only after authorized verification, but it addresses a different concern. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. It cannot establish a safe correction. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This alternative addresses Sudoers least privilege and safe editing, not the specific issue of SSH user keys, authorized_keys and agent handling: sudo applies policy to which user may execute particular commands as another identity; unrestricted root privileges and unvalidated configuration edits are avoidable risks. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This alternative addresses SSH server host keys and client trust decisions, not the specific issue of SSH user keys, authorized_keys and agent handling: SSH server host keys identify the remote server and protect against impersonation; host keys are different from user public-key authentication keys. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

That option would compare server host key fingerprint to an approved inventory, inspect /etc/ssh/ssh_host_* files and examine the user's known_hosts entry, but it addresses a different concern. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

That option would inspect `systemctl list-sockets`, service and socket unit states, live listeners and a controlled remote connection attempt, but it addresses a different concern. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. It cannot establish a safe correction. ssh/authorized_keys file instead of the public key.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. It cannot establish a safe correction. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This alternative addresses SSH server host keys and client trust decisions, not the specific issue of SSH user keys, authorized_keys and agent handling: Clients recognize the correct unique server identity and unexpected key changes trigger investigation rather than silent acceptance. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This alternative addresses Discovering exposed sockets and services, not the specific issue of SSH user keys, authorized_keys and agent handling: Only approved interfaces and ports remain reachable, with a recorded accountable owner for each listening network service. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This alternative addresses SSH port forwarding and X11 tunnel purpose, not the specific issue of SSH user keys, authorized_keys and agent handling: Expose the internal service to every interface as a substitute for an SSH tunnel and assume -X forwards arbitrary TCP services exactly like -L. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This alternative addresses Shadow password file permissions and hash protection, not the specific issue of SSH user keys, authorized_keys and agent handling: Make `/etc/shadow` readable by all users and place password hashes into `/etc/passwd` because hashed values are harmless to disclose. ssh/authorized_keys file instead of the public key. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

That option would disable strict host-key checking permanently and copy one VM image's SSH host private keys unchanged to every clone, but it addresses a different concern. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This alternative addresses Shadow password file permissions and hash protection, not the specific issue of SSH user keys, authorized_keys and agent handling: Restore restricted shadow database ownership and permissions using distribution-supported account tools and protect password hashes from general reads. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

That option would use `who`, `w` and `last` to distinguish active from historical logins and apply appropriate shell or PAM resource limits with ulimit and policy, but it addresses a different concern. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. It cannot establish a safe correction. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This alternative addresses GnuPG signing versus encryption and key revocation, not the specific issue of SSH user keys, authorized_keys and agent handling: Encryption protects content for holders of the corresponding decryption key, whereas a digital signature demonstrates origin and integrity without concealing the data. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This alternative addresses Login history, active sessions and process limits, not the specific issue of SSH user keys, authorized_keys and agent handling: Current sessions and login history answer different operational questions; per-process shell resource limits can constrain activity but are not equivalent to user authentication policies. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

That option would run carefully scoped `find` checks for -perm -4000 and -perm -2000, review file ownership, ACLs, package provenance and intended use, but it addresses a different concern. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This alternative addresses Disabling unnecessary systemd and socket-activated services, not the specific issue of SSH user keys, authorized_keys and agent handling: Inspect `systemctl list-sockets`, service and socket unit states, live listeners and a controlled remote connection attempt.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. It cannot establish a safe correction. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This alternative addresses TCP wrappers legacy access control and modern alternatives, not the specific issue of SSH user keys, authorized_keys and agent handling: The intended client restrictions are enforced by a mechanism the actual running service honors rather than by unused legacy files. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This alternative addresses SSH port forwarding and X11 tunnel purpose, not the specific issue of SSH user keys, authorized_keys and agent handling: The authorized client reaches only the intended remote service or graphical display without exposing the server's internal listening port publicly. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This alternative addresses Discovering exposed sockets and services, not the specific issue of SSH user keys, authorized_keys and agent handling: Combine local `ss` or `lsof` socket ownership checks with authorized nmap testing to identify exposed services and unnecessary listeners. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts. Appropriate response: Install only the user's public key in the authorized_keys file, protect the private key and use ssh-agent or ssh-add when appropriate for approved key handling. Root-cause evidence: Inspect key file permissions, the authorized_keys contents, ssh -v authentication trace and `ssh-add -l` for an intended agent. Independent acceptance: Authorized users authenticate with their own protected private keys and the remote host contains no copied private credential.

This shortcut is unsafe for the present Linux issue: Copy the private SSH key to authorized_keys on the server and make both key files world-readable to reduce login errors. Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.

This alternative addresses Disabling unnecessary systemd and socket-activated services, not the specific issue of SSH user keys, authorized_keys and agent handling: Inspect `systemctl list-sockets`, service and socket unit states, live listeners and a controlled remote connection attempt. Linux principle: Public keys can authorize remote login while the private key remains secret; agent software can hold usable key identities without copying secrets to remote hosts.