Typically, if you are working with multiple accounts and/or multiple machines, you benefit from creating multiple SSH identities. In Mac OS X, GitBash, and Linux you can use the three ssh- commands to create and manage your identities.

SSH CommandPurpose
ssh-keygenCreates key pairs.
ssh-agentAgent for providing keys to remote servers. The agent holds loaded keys in memory.
ssh-addLoads a private key into the agent.

To support multiple SSH identities in , do the following:

Create multiple identities for Mac OS X, GitBash, and Linux

You should at this point already have created at least a single default identity. To see if you have a default identity already, list the contents of your .ssh directory. Default identity files appear as a id_encrypt and id_encrypt.pub pair. The encrypt value is either rsa or dsa. Use the ssh-keygen command to create a new identity. In the example below, the identity is named personalid.

$ ssh-keygen -f ~/.ssh/personalid -C "personalid"
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /Users/manthony/.ssh/personalid.
Your public key has been saved in /Users/manthony/.ssh/personalid.pub.
The key fingerprint is:
7a:9c:b2:9c:8e:4e:f4:af:de:70:77:b9:52:fd:44:97 personalid
The key's randomart image is:
+--[ RSA 2048]----+
|         |
|         |
|        .|
|        Eo|
|  .  S  . ..|
|  . . o . ... .|
|  . = = ..o o |
|  . o X ... . .|
|  .ooB.o ..  |

If you have multiple Bitbucket accounts, you need to generate a new public/private key pair for each account.

Create a SSH config file

When you have multiple identity files, consider creating an SSH config file to create aliases for your various identities. You can construct a SSH config file using many parameters and different approaches. The format for the alias entries used in this example is:

Host alias
HostName bitbucket.org
IdentityFile ~/.ssh/identity

To create a config file for two identities (workid and personalid), you would do the following:

  1. Open a terminal window.
  2. Edit the ~/.ssh/config file.
    If you don't have a config file, create one.
  3. Add an alias for each identity combination for example:

    Host workid
     HostName bitbucket.org
     IdentityFile ~/.ssh/workid
    Host personalid
     HostName bitbucket.org
     IdentityFile ~/.ssh/personalid
  4. Close and save the file.

Now, you can substitute the alias for portions of the repository URL address as illustrated in the following table:

DVCSDefault addressAddress with alias
Mercurialssh://hg@bitbucket.org/<username>/<reponame>/ssh://hg@alias /<username>/<reponame>/

There are lots of ways to use SSH aliasing. Another common use case may be the situation where you are using Bitbucket and GitHub on the same machine. The codingbadger suggested the following configuration for that use case:

# Default GitHub user
Host github.com
 HostName github.com
 PreferredAuthentications publickey
 IdentityFile ~/.ssh/personalid
# Work user account
Host bitbucket.org
 HostName bitbucket.org
 PreferredAuthentications publickey
 IdentityFile ~/.ssh/workid

If you google for "ssh aliases" or "ssh aliasing" you may find examples that suit you needs better.

Configure compression for Mercurial

Load each key into the appropriate Bitbucket account

Load each public key into the corresponding account. If you have an account with a repository you access from two identities, you can load two keys into that account – one for each identity. Use the following procedure to load each key into your Bitbucket accounts:

  1. From your avatar in the bottom left, click Bitbucket settings.
    Bitbucket displays the Account settings page.
  2. Click SSH keys.
    The SSH Keys page displays. If you have any existing keys, those appear on this page.
  3. Back in your terminal window, copy the contents of your public key file.
    For example, in Linux you can cat the contents.

    cat ~/.ssh/id_rsa.pub

    In Mac OSX, the following command copies the output to the clipboard:

    pbcopy < ~/.ssh/id_rsa.pub
  4. Back in your browser, enter a Label for your new key, for example, Default public key.

  5. Paste the copied public key into the SSH Key field:
  6. Press Add key.
    The system adds the key to your account. Bitbucket sends you an email to confirm addition of the key. 

Ensure the ssh-agent is running and loaded with your keys

Most modern operating systems (and GitBash) start a ssh-agent running for you. However, it is important you know how to check for a running agent and start one if necessary.

  1. Open a terminal window and enter the appropriate command for your operating system.

    GitBashMac OS X andLinux
    $ ps | grep ssh-agent
    5192 1 5192 5192 ? 500 19:23:34 /bin/ssh-agent

    If for some reason the agent isn't running, start it by entering eval ssh-agent at the command line. You should only be running a single instance of ssh-agent. If you have multiple instances running, use the kill PID command to stop each of them. Then, restart a single instance.

    $ ps -e | grep [s]sh-agent
    9060 ?? 0:00.28 /usr/bin/ssh-agent -l

    If the agent isn't running, start it by hand. The format for starting the command manually is:

    $ eval ssh-agent $SHELL

    $SHELL is the environment variable for your login shell.

  2. List the currently loaded keys:

    $ ssh-add -l
    2048 68:ef:d6:1e:4b:3b:a3:52:6f:b0:c3:4b:da:e8:d1:9f /c/Documents and Settings/manthony/.ssh/personalid (RSA)
  3. If necessary, add your new key to the list:

    $ ssh-add ~/.ssh/workid
    Enter passphrase for /c/Documents and Settings/manthony/.ssh/workid:
    Identity added: /c/Documents and Settings/manthony/.ssh/workid (/c/Documents and Settings/manthony/.ssh/workid)
  4. List the keys again to verify the add was successful:

    $ ssh-add -l
    2048 68:ef:d6:1e:4b:3b:a3:52:6f:b0:c3:4b:da:e8:d1:9f /c/Documents and Settings/manthony/.ssh/personalid (RSA)
    2048 1b:24:fe:75:4d:d2:31:a9:d5:4e:65:60:7c:60:7a:a3 /c/Documents and Settings/manthony/.ssh/workid (RSA)

Clone a repository using SSH and your alias configuration

To clone a repository with one of multiple SSH identities that you configured, you clone the repo and using your alias in the SSH URL.  To try this for yourself, log into Bitbucket and do the following:

  1. Navigate to the repository Overview.
  2. Display the SSH URL.
    For example, Bitbucket displays its tutorial URL as:
    hg clone ssh://hg@bitbucket.org/tutorials/tutorials.bitbucket.org
  3. Open a terminal window on your system.

  4. Navigate to the directory where you store your repositories.

  5. Enter the command but substitute your config alias appropriately.

    For example, if you want to use your personalid alias to enter the clone you enter:

    hg clone ssh://hg@personalid/tutorials/tutorials.bitbucket.org

    The system clones the repository for you.

  6. Change directory to the repository.

  7. Display the contents of the repository's configuration. 

    $ cat .hg/hgrc
    default = ssh://hg@tutorials/tutorials/tutorials.bitbucket.org

    Notice that the DVCS stored the URL you used for the clone; the URL that includes your alias. Now, moving forward for this repository, the DVCS uses the URL that includes the SSH alias.

Change existing repositories from HTTPS to SSH (optional)

You can change existing repository configurations to use a SSH configuration that makes use of your multiple identities. You'll only need to do this for repositories that you have already cloned with HTTPS or for repositories where you want to change an existing SSH specification. For example, if you used SSH to clone a repository in the past and now want to set it up to use another SSH key.

Git configuration

  1. Open a terminal window.
  2. Navigate to the repository configuration file (REPO_INSTALLDIR/.git).

  3. Open the config file with your favorite editor.

  4. Locate the url value in the [remote "origin"] section

    [remote "origin"]
      fetch = +refs/heads/*:refs/remotes/origin/*
      url = https://newuserme@bitbucket.org/newuserme/bb101repo.git

    In this example, the url is using the HTTPS protocol. 

  5. Change the url value to use the SSH format for your repository.
    When you are done you should see something similar to the following:

    [remote "origin"]
      fetch = +refs/heads/*:refs/remotes/origin/*
      url = git@personalid:newuserme/bb101repo.git

Mercurial Configuration

  1. Open a terminal window.
  2. Navigate to the repository configuration file (REPO_INSTALLDIR/.hg).

  3. Open the hgrc file with your favorite editor.

    default = https://newuserme@staging.bitbucket.org/newuserme/bb101repo
  4. Change the [paths] default to:

    default = ssh://hg@bitbucket.org/newuserme/bb101repo
  5. Save and close the file.

 My thanks to the codingbadger and to Charles on the Bitbucket team who helped me get my head around this technique. Any errors here are of my own making of course.