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On macOS, Linux, and other Unix-like systems that use POSIX permissions, restrict the private key so only its owner can read and write it: chmod 600 /path/to/private_key. Replace the example path with the actual identity file SSH is using. OpenSSH ignores a private key file that is accessible by others, so making it more permissive is not a fix.
What the “permissions too open” warning means
OpenSSH checks that a private identity file is protected from access by other users. Its ssh(1) manual says it “will simply ignore a private key file if it is accessible by others.” The warning is therefore a security check: the client may refuse to use that identity, rather than authenticate with it.
The remedy is usually to restrict access to the existing private key. This warning alone does not mean the key must be replaced or regenerated.
Fix the private key on macOS, Linux, or another Unix-like system
1. Identify the exact private-key file
Common filenames include ~/.ssh/id_ed25519 and ~/.ssh/id_rsa, but SSH can use a custom path. Check the command’s -i option or the relevant IdentityFile setting, and make sure you are changing the identity file actually being offered. Do not assume a similarly named file is the one causing the warning.
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A matching filename ending in .pub is generally the public key, which is shared with the server. The private key is the credential you must protect; see the OpenSSH manual’s description of identity files and public-key authentication.
2. Inspect and restrict its permissions
Use ls -l to inspect the file, then set the private key to owner read/write only:
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ls -l /path/to/private_key
chmod 600 /path/to/private_keyIn POSIX mode 600, the owner can read and write the file; group and other users have no access. This matches the OpenSSH requirement that the key be readable by its owner but inaccessible to others. Use the same actual path in both commands.
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3. Check the parent directory and ownership if the warning remains
If the private key is restricted but SSH still complains, inspect the containing .ssh directory and confirm the key belongs to the account that is using it. OpenBSD’s ssh(1) manual recommends that the .ssh directory be accessible to its owner and inaccessible to others. It also says the SSH configuration file must not be writable by others; that is a related check, not a reason to change unrelated files blindly.
If you use ssh-agent
ssh-add loads private-key identities into ssh-agent, and it has its own access check: its manual says identity files should not be readable by anyone but the user and that it ignores files accessible by others. See OpenBSD’s ssh-add(1) manual.
If direct SSH login works but adding a key to the agent fails, verify that ssh-add is receiving the same private-key path you corrected. A different identity file can have different permissions.
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Windows permissions are a separate case
The chmod 600 instructions apply to Unix-style POSIX file permissions. Windows OpenSSH may rely on access-control lists (ACLs), and the exact correction can depend on the Windows release, filesystem, and account setup. Do not treat the Unix command as a universal Windows fix; use instructions verified for the specific Windows environment and SSH client involved.
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Keep the private and public keys distinct
The public key is provided to the server for authentication; the private key remains with the user and must be protected. The “private key accessible by others” warning concerns the private identity file, not the public key. That distinction does not mean public-key files or their directories should be made writable by everyone.
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