Generate key

SSH keys can be generated using the ssh-keygen utility. The following table shows utility’s most useful parameters.

Option	Description
-t type	Key type to create (rsa, ed25519, ecdsa). ed25519 is recommended.
-b bits	Number of bits in the key (e.g. 4096 for RSA). Ignored for ed25519.
-C comment	Comment to add to the key (e.g. your email for GitHub).
-f filename	File in which to save the key (default: ~/.ssh/id_<type>).
-N passphrase	New passphrase for the key (empty string for no passphrase).
-y	Read a private key and print the corresponding public key.
-l -f keyfile	Show fingerprint of the given public/private key file.
-E hash_alg	Fingerprint hash algorithm (md5, sha256). Default is sha256.
-p	Change the passphrase of a private key.
-R hostname	Remove all keys belonging to a hostname from ~/.ssh/known_hosts.
-F hostname	Search ~/.ssh/known_hosts for entries matching a hostname.
-A	Generate host keys of all types (used for SSH servers).
-q	Quiet mode – suppress most messages.

Comment (-C)

The -C parameter allow you to set a comment that will be written to the public key file and can be used by third-party services.

Note: Some guides recommend using your exact email address here, but you can use whatever you like.

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The following cell generates the ssh key and adds “some arbitrary comment” to it.

rm -rf /tmp/ssh_experiments
mkdir /tmp/ssh_experiments
ssh-keygen -C "some arbitrary comment" -f /tmp/ssh_experiments/my_super_key -N ""

Generating public/private ed25519 key pair.
Your identification has been saved in /tmp/ssh_experiments/my_super_key
Your public key has been saved in /tmp/ssh_experiments/my_super_key.pub
The key fingerprint is:
SHA256:C5HQJWqgLyHXGszLLtZTRHUfQHcmNWKmSfBwfiNHmQU some arbitrary comment
The key's randomart image is:
+--[ED25519 256]--+
|  . .oo=+*.E**   |
| + o.o.oB Oo* .  |
|+ = +.o  * =     |
|.= =.  .  + .    |
|. =  .. S        |
| o. .  . .       |
|...o    .        |
|..  .            |
|                 |
+----[SHA256]-----+

The following cell prints ssh key generated in the previous code.

cat /tmp/ssh_experiments/my_super_key.pub

ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICzvRTr8SmN5lC2N5j1bVMNViBqR2VnG94HRjOrYJerq some arbitrary comment

After the ssh key, write the exact comment specified in the -C option as raw text.