[docs] Update List Keypairs cleos How-to - 2.0

docs/02_cleos/02_how-to-guides/how-to-list-all-key-pairs.md

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+## Overview
+
+This how-to guide provides instructions on how to list all public keys and public/private key pairs within the `keosd` default wallet. You can use the public and private keys to authorize transactions in an EOSIO blockchain. 
+
+The example in this how-to guide displays all public keys and public/private key pairs stored within the existing default wallet.
+
+## Before you begin
+
+Make sure you meet the following requirements:
+
+* Create a default wallet using the `cleos wallet create` command. See the [How to Create a Wallet](../02_how-to-guides/how-to-create-a-wallet.md) section for instructions. 
+* [Create a keypair](../03_command-reference/wallet/create_key.md) within the default wallet.
+* Familiarize with the [`cleos wallet`](../03_command-reference/wallet/index.md) commands.
+* Install the currently supported version of `cleos`.
+[[info | Note]]
+| `cleos` is bundled with the EOSIO software. [Installing EOSIO](../../00_install/index.md) will also install `cleos`.
+* Understand what a [public key](https://developers.eos.io/welcome/latest/glossary/index/#public-key) and [private key](https://developers.eos.io/welcome/latest/glossary/index/#private-key) is.
+
+## Command Reference
+
+See the following reference guide for `cleos` command line usage and related options:
+
+* [`cleos wallet keys`](../03_command-reference/wallet/keys.md) command and its parameters
+* [`cleos wallet private_keys`](../03_command-reference/wallet/private_keys.md) command its parameters
+
+## Procedure
+
+The following steps show how to list all public keys and public/private key pairs stored within the `keosd` default wallet:
+
+1. Open the default wallet:
+```sh
+cleos wallet open
+```
+```console
+Opened: default
+```
+
+2. Unlock the default wallet. The command will prompt to enter a password:
+```sh
+cleos wallet unlock
+```
+```console
+password:
+```
+
+3. Enter the generated password when you created the default wallet:
+```sh
+***
+```
+If the password is correct, the wallet gets unlocked:
+```console
+Unlocked: default
+```
+
+4. List all public keys within the default wallet:
+```sh
+cleos wallet keys
+```
+**Example Output**
+```console
+[
+  "EOS5VCUBtxS83ZKqVcWtDBF4473P9HyrvnCM9NBc4Upk1C387qmF3"
+]
+```
+
+5. List all public/private key pairs withing the default wallet. The command will prompt to enter a password:
+```sh
+cleos wallet private_keys
+```
+```console
+password:
+```
+
+6. Enter the generated password when you created the default wallet: 
+```sh
+***
+```
+**Example Output**  
+If the password is correct, the public/private key pairs are listed:
+```console
+password: [[
+    "EOS5VCUBt****************************************F3",
+    "5JnuuGM1S****************************************4D"
+  ]
+]
+```
+
+[[caution | Warning]]
+| Never reveal your private keys in a production environment. 
+
+[[info | Note]]
+| If the above commands does not list any keys, make sure you have created keypairs and imported private keys to your wallet.
+
+## Summary
+
+By following these instructions, you are able to list all the public keys and public/private key pairs stored within the `keosd` default wallet.
+
+## Troubleshooting
+
+When you run the `cleos wallet open/unlock` commands, you may encounter the following CLI error:
+
+```sh
+cleos wallet open
+```
+```console
+No wallet service listening on ***. Cannot automatically start keosd because keosd was not found.
+Failed to connect to keosd at unix:///Users/xxx.xxx/eosio-wallet/keosd.sock; is keosd running?
+```
+
+To fix this error, make sure the `keosd` utility is running on your machine:
+```sh
+keosd
+```