To enable SSH key login, create or locate a key pair on your computer, copy the public key to the server account you will use, and save it in that account’s accepted-key file. Keep the private key on your computer. For a typical OpenSSH account, the destination is ~/.ssh/authorized_keys; Windows OpenSSH servers use a different path for administrator accounts.
Know which key goes where
An SSH key pair has a public half and a private half. The public key is usually the file ending in .pub; it is the part you install on the server. Keep the matching private key on your client and do not copy it to the server. The public-key file’s contents are added to authorized_keys on each account where that key should permit login. See the OpenSSH ssh-keygen manual.
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This is your user-authentication key, not the server’s host key. Host keys identify the server to clients; your public key lets the server authorize your account.
Generate a key or find one you already have
On Linux, macOS, or Windows with OpenSSH installed, run ssh-keygen and follow the prompts to select a save path and passphrase. If you already have a key pair, locate its matching public-key file rather than generating another unnecessarily. Keep the private key protected on the client; a passphrase can add protection if the private-key file is exposed.
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Key algorithms and accepted policies depend on the installed OpenSSH version and the server’s configuration, so follow your organization’s requirements rather than assuming one algorithm works everywhere. Microsoft’s Windows guidance documents ssh-keygen and lists DSA, RSA, ECDSA, and Ed25519 support; it identifies Ed25519 as the default when no algorithm is specified. See Microsoft’s OpenSSH key management guide.
Install the key on a standard OpenSSH account
For a typical OpenSSH account, add the complete public-key line to ~/.ssh/authorized_keys in the target user’s home directory. The file is plain text with one key per line. Preserve the full line; its key type and encoded key are essential, while any trailing comment is just an identifier.
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- Connect to the server using a password or another authorized method, or have an administrator do this for you.
- Create the directory if needed:
mkdir -p ~/.ssh. - Append the public key: use a trusted transfer method such as
scpor paste the public-key line into~/.ssh/authorized_keysin an authorized server session. Append it rather than overwriting existing keys. - Restrict access: OpenSSH recommends that the
.sshdirectory andauthorized_keysfile not be accessible by other users. On a Unix-like OpenSSH server, a common setup ischmod 700 ~/.sshandchmod 600 ~/.ssh/authorized_keys. The server’s policy and configuration are authoritative.
If your client has ssh-copy-id, it can copy a public key to an OpenSSH account when you have an initial login method. It is a convenience, not a requirement. The server may use another location through its AuthorizedKeysFile setting, or the account’s home directory may differ from the usual layout. Check the server configuration or ask its administrator if the default path does not work. OpenSSH documents the file format and permission checks in its sshd manual.
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First ensure that OpenSSH Server is installed, the sshd service is running, and the inbound firewall rule permits SSH connections. Windows installation state and setup steps depend on the Windows release; Microsoft documents these in its OpenSSH installation and first-use guide.
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The accepted-key file depends on the Windows account type:
| Windows account | Public-key file | Access rule |
|---|---|---|
| Standard user | C:Usersusername.sshauthorized_keys |
Use permissions that prevent other users from accessing the key file. |
| Member of the local Administrators group | C:ProgramDatasshadministrators_authorized_keys |
Allow only NT AuthoritySYSTEM and BUILTINAdministrators. |
For an administrator account, do not put the key only in the user profile’s .sshauthorized_keys; Windows OpenSSH uses the shared administrator key file instead. Microsoft provides the icacls command for setting that file’s required ACLs. Follow the account-specific instructions in Microsoft’s key management guide; Unix chmod permissions do not replace Windows ACLs.
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Microsoft documents this key-based flow for local and Active Directory accounts, but not Microsoft Entra ID accounts. Windows OpenSSH also does not support AuthorizedKeysCommand or AuthorizedKeysCommandUser; these are Windows-specific limitations, not general OpenSSH rules.
Test the connection
From the client, connect with the account name and server address:
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ssh username@serverIf the private key is not in a default location or loaded into an agent, specify its path with -i:
ssh -i path/to/private_key username@serverReplace the example username, server, and key path with your actual values. If the connection is rejected, client-side verbose output can help reveal what is happening:
ssh -v username@serverFix “Permission denied (publickey)”
Check the cause on the server side first, then confirm you are connecting as the intended account:
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- Wrong key-file path: confirm the account’s actual home directory and the server’s
AuthorizedKeysFilesetting. On Windows, check whether the target is a standard user or a local administrator. - Incomplete public-key line: make sure the full line from the client’s
.pubfile appears in the accepted-key file as a single line, without wrapping, truncation, or accidental edits. - Permissions or ACLs: ensure the server accepts the ownership and access settings on the key file and its containing directory. For a Windows administrator key file, check the specified SYSTEM and Administrators ACLs.
- Wrong private key offered: if you have several keys, try the matching private key explicitly with
-i.
Microsoft’s OpenSSH connection troubleshooting guide lists missing or incorrect authorized_keys files and improper permissions among causes of public-key authentication failures.
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