sshadd

sshadd is commonly a misspelling of ssh-add, an OpenSSH utility that loads private keys into the SSH authentication agent (ssh-agent). The agent holds unlocked keys in memory for the duration of a session, enabling passwordless authentication to multiple remote systems without retyping passphrases.

How it works: ssh-add communicates with the running ssh-agent to add identities. Keys remain available to ssh, scp, and sftp as long as the agent is running and the key is not removed. If the key is encrypted with a passphrase, ssh-add will prompt for it the first time the key is added or when the agent restarts.

Basic usage: The syntax is ssh-add [options] [file ...]. If no file is given, ssh-add attempts to load default identities from the user's ~/.ssh directory (for example id_rsa, id_ecdsa).

Common options include -l to list loaded identities and -L to print their public keys, -D to delete all identities, -d to delete a specific identity, and -t to set a maximum lifetime for a loaded key (in seconds).

Examples: ssh-add to prompt for all private keys in default locations; ssh-add ~/.ssh/id_rsa to load a specific key; ssh-add -D to remove all keys; ssh-add -t 3600 ~/.ssh/id_rsa to load a key with a one-hour lifetime.

Security considerations: The agent detaches from the terminal; ensure the host is trusted. When using agent forwarding, keys loaded into the agent may be used on remote systems; disable forwarding on untrusted hosts if possible. Protect the local agent by locking the keyring when not in use and by using a passphrase on private keys.

Note: There is no separate tool named sshadd; the standard utility is ssh-add, part of OpenSSH; some users refer to it informally as sshadd.