Troubleshoot connecting to your instance - Amazon Elastic Compute Cloud
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Troubleshoot connecting to your instance

The following information and common errors can help you troubleshoot connecting to your Linux instance.

To troubleshoot connecting to Windows instances, see Troubleshoot Windows instances in the Amazon EC2 User Guide for Windows Instances.

Common causes for connection issues

We recommend that you start to troubleshoot instance connection problems by verifying that you have accurately performed the following tasks.

Verify the username for your instance

You can connect to your instance using the username for your user account or the default username for the AMI that you used to launch your instance.

  • Get the username for your user account.

    For more information about how to create a user account, see Manage users on your Linux instance.

  • Get the default username for the AMI that you used to launch your instance:

    AMI used to launch instance Default username

    AL2023

    Amazon Linux 2

    Amazon Linux

    ec2-user
    CentOS centos or ec2-user
    Debian admin
    Fedora fedora or ec2-user
    RHEL ec2-user or root
    SUSE ec2-user or root
    Ubuntu ubuntu
    Oracle ec2-user
    Bitnami bitnami
    Rocky Linux rocky
    Other Check with the AMI provider
Verify that your security group rules allow traffic

Ensure that the security group associated with your instance allows incoming SSH traffic from your IP address. The default security group for the VPC does not allow incoming SSH traffic by default. The security group created by the launch instance wizard enables SSH traffic by default. For steps to add a rule for inbound SSH traffic to your Linux instance, see Authorize inbound traffic for your Linux instances. For steps to verify, see Error connecting to your instance: Connection timed out.

Verify that your instance is ready

After you launch an instance, it can take a few minutes for the instance to be ready so that you can connect to it. Check your instance to make sure it is running and has passed its status checks.

  1. Open the Amazon EC2 console at https://console.amazonaws.cn/ec2/.

  2. In the navigation pane, choose Instances, and then select your instance.

  3. Verify the following:

    1. In the Instance state column, verify that your instance is in the running state.

    2. In the Status check column, verify that your instance has passed the two status checks.

Verify that you've satisfied all prerequisites to connect

Ensure that you have all the information you need to connect. For more information, see Connect to your Linux instance.

For prerequisites specific to connection types, such as SSH, EC2 Instance Connect, OpenSSH, PuTTY, and more, see the following options.

Linux or macOS X

If your local computer operating system is Linux or macOS X, check the specific prerequisites for the following connection options:

Windows

If your local computer operating system is Windows, check the specific prerequisites for the following connection options:

Error connecting to your instance: Connection timed out

If you try to connect to your instance and get the error message Network error: Connection timed out or Error connecting to [instance], reason: -> Connection timed out: connect, try the following:

Check your security group rules.

You need a security group rule that allows inbound traffic from your local computer's public IPv4 address on the proper port.

  1. Open the Amazon EC2 console at https://console.amazonaws.cn/ec2/.

  2. In the navigation pane, choose Instances, and then select your instance.

  3. On the Security tab at the bottom of the console page, under Inbound rules, check the list of rules that are in effect for the selected instance.

    • For Linux instances: Verify that there is a rule that allows traffic from your local computer to port 22 (SSH).

    • For Windows instances: Verify that there is a rule that allows traffic from your local computer to port 3389 (RDP).

    If your security group does not have a rule that allows inbound traffic from your local computer, add a rule to your security group. For more information, see Authorize inbound traffic for your Linux instances.

  4. For the rule that allows inbound traffic, check the Source field. If the value is a single IP address, and if the IP address is not static, a new IP address will be assigned each time you restart your computer. This will result in the rule not including your computer's IP address traffic. The IP address might not be static if your computer is on a corporate network, or you're connecting through an internet service provider (ISP), or your computer IP address is dynamic and changes each time you restart your computer. To ensure that your security group rule allows inbound traffic from your local computer, instead of specifying a single IP address for Source, rather specify the range of IP addresses used by your client computers.

    For more information about security group rules, see Security group rules in the Amazon VPC User Guide.

Check the route table for the subnet.

You need a route that sends all traffic destined outside the VPC to the internet gateway for the VPC.

  1. Open the Amazon EC2 console at https://console.amazonaws.cn/ec2/.

  2. In the navigation pane, choose Instances, and then select your instance.

  3. On the Networking tab, make note of the values for VPC ID and Subnet ID.

  4. Open the Amazon VPC console at https://console.amazonaws.cn/vpc/.

  5. In the navigation pane, choose Internet Gateways. Verify that there is an internet gateway attached to your VPC. Otherwise, choose Create internet gateway, enter a name for the internet gateway, and choose Create internet gateway. Then, for the internet gateway you created, choose Actions, Attach to VPC, select your VPC, and then choose Attach internet gateway to attach it to your VPC.

  6. In the navigation pane, choose Subnets, and then select your subnet.

  7. On the Route table tab, verify that there is a route with 0.0.0.0/0 as the destination and the internet gateway for your VPC as the target. If you're connecting to your instance using its IPv6 address, verify that there is a route for all IPv6 traffic (::/0) that points to the internet gateway. Otherwise, do the following:

    1. Choose the ID of the route table (rtb-xxxxxxxx) to navigate to the route table.

    2. On the Routes tab, choose Edit routes. Choose Add route, use 0.0.0.0/0 as the destination and the internet gateway as the target. For IPv6, choose Add route, use ::/0 as the destination and the internet gateway as the target.

    3. Choose Save routes.

Check the network access control list (ACL) for the subnet.

The network ACLs must allow inbound traffic from your local IP address on port 22 (for Linux instances) or port 3389 (for Windows instances). It must also allow outbound traffic to the ephemeral ports (1024-65535).

  1. Open the Amazon VPC console at https://console.amazonaws.cn/vpc/.

  2. In the navigation pane, choose Subnets.

  3. Select your subnet.

  4. On the Network ACL tab, for Inbound rules, verify that the rules allow inbound traffic from your computer on the required port. Otherwise, delete or modify the rule that is blocking the traffic.

  5. For Outbound rules, verify that the rules allow outbound traffic to your computer on the ephemeral ports. Otherwise, delete or modify the rule that is blocking the traffic.

If your computer is on a corporate network

Ask your network administrator whether the internal firewall allows inbound and outbound traffic from your computer on port 22 (for Linux instances) or port 3389 (for Windows instances).

If you have a firewall on your computer, verify that it allows inbound and outbound traffic from your computer on port 22 (for Linux instances) or port 3389 (for Windows instances).

Check that your instance has a public IPv4 address.

If not, you can associate an Elastic IP address with your instance. For more information, see Elastic IP addresses.

Check the CPU load on your instance; the server may be overloaded.

Amazon automatically provides data such as Amazon CloudWatch metrics and instance status, which you can use to see how much CPU load is on your instance and, if necessary, adjust how your loads are handled. For more information, see Monitor your instances using CloudWatch.

To connect to your instance using an IPv6 address, check the following:

  • Your subnet must be associated with a route table that has a route for IPv6 traffic (::/0) to an internet gateway.

  • Your security group rules must allow inbound traffic from your local IPv6 address on the proper port (22 for Linux and 3389 for Windows).

  • Your network ACL rules must allow inbound and outbound IPv6 traffic.

  • If you launched your instance from an older AMI, it might not be configured for DHCPv6 (IPv6 addresses are not automatically recognized on the network interface). For more information, see Configure IPv6 on your instances in the Amazon VPC User Guide.

  • Your local computer must have an IPv6 address, and must be configured to use IPv6.

Error: unable to load key ... Expecting: ANY PRIVATE KEY

If you try to connect to your instance and get the error message, unable to load key ... Expecting: ANY PRIVATE KEY, the file in which the private key is stored is incorrectly configured. If the private key file ends in .pem, it might still be incorrectly configured. A possible cause for an incorrectly configured private key file is a missing certificate.

If the private key file is incorrectly configured, follow these steps to resolve the error
  1. Create a new key pair. For more information, see Create a key pair using Amazon EC2.

    Note

    Alternatively, you can create a new key pair using a third-party tool. For more information, see Create a key pair using a third-party tool and import the public key to Amazon EC2.

  2. Add the new key pair to your instance. For more information, see I've lost my private key. How can I connect to my Linux instance?.

  3. Connect to your instance using the new key pair.

Error: User key not recognized by server

If you use SSH to connect to your instance
  • Use ssh -vvv to get triple verbose debugging information while connecting:

    ssh -vvv -i path/key-pair-name.pem instance-user-name@ec2-203-0-113-25.compute-1.amazonaws.com.cn

    The following sample output demonstrates what you might see if you were trying to connect to your instance with a key that was not recognized by the server:

    open/ANT/myusername/.ssh/known_hosts). debug2: bits set: 504/1024 debug1: ssh_rsa_verify: signature correct debug2: kex_derive_keys debug2: set_newkeys: mode 1 debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug2: set_newkeys: mode 0 debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug2: key: boguspem.pem ((nil)) debug1: Authentications that can continue: publickey debug3: start over, passed a different list publickey debug3: preferred gssapi-keyex,gssapi-with-mic,publickey,keyboard-interactive,password debug3: authmethod_lookup publickey debug3: remaining preferred: keyboard-interactive,password debug3: authmethod_is_enabled publickey debug1: Next authentication method: publickey debug1: Trying private key: boguspem.pem debug1: read PEM private key done: type RSA debug3: sign_and_send_pubkey: RSA 9c:4c:bc:0c:d0:5c:c7:92:6c:8e:9b:16:e4:43:d8:b2 debug2: we sent a publickey packet, wait for reply debug1: Authentications that can continue: publickey debug2: we did not send a packet, disable method debug1: No more authentication methods to try. Permission denied (publickey).
If you use PuTTY to connect to your instance
  • Verify that your private key (.pem) file has been converted to the format recognized by PuTTY (.ppk). For more information about converting your private key, see Connect to your Linux instance from Windows with PuTTY.

    Note

    In PuTTYgen, load your private key file and select Save Private Key rather than Generate.

  • Verify that you are connecting with the appropriate user name for your AMI. Enter the user name in the Host name box in the PuTTY Configuration window.

    AMI used to launch instance Default username

    AL2023

    Amazon Linux 2

    Amazon Linux

    ec2-user
    CentOS centos or ec2-user
    Debian admin
    Fedora fedora or ec2-user
    RHEL ec2-user or root
    SUSE ec2-user or root
    Ubuntu ubuntu
    Oracle ec2-user
    Bitnami bitnami
    Rocky Linux rocky
    Other Check with the AMI provider
  • Verify that you have an inbound security group rule to allow inbound traffic to the appropriate port. For more information, see Authorizing Network Access to Your Instances.

Error: Permission denied or connection closed by [instance] port 22

If you connect to your instance using SSH and get any of the following errors, Host key not found in [directory], Permission denied (publickey), Authentication failed, permission denied, or Connection closed by [instance] port 22, verify that you are connecting with the appropriate user name for your AMI and that you have specified the proper private key (.pem) file for your instance.

The appropriate user names are as follows:

AMI used to launch instance Default username

AL2023

Amazon Linux 2

Amazon Linux

ec2-user
CentOS centos or ec2-user
Debian admin
Fedora fedora or ec2-user
RHEL ec2-user or root
SUSE ec2-user or root
Ubuntu ubuntu
Oracle ec2-user
Bitnami bitnami
Rocky Linux rocky
Other Check with the AMI provider

For example, to use an SSH client to connect to an Amazon Linux instance, use the following command:

ssh -i /path/key-pair-name.pem instance-user-name@ec2-203-0-113-25.compute-1.amazonaws.com.cn

Confirm that you are using the private key file that corresponds to the key pair that you selected when you launched the instance.

  1. Open the Amazon EC2 console at https://console.amazonaws.cn/ec2/.

  2. In the navigation pane, choose Instances and then select your instance.

  3. On the Details tab, under Instance details, verify the value of Key pair name.

  4. If you did not specify a key pair when you launched the instance, you can terminate the instance and launch a new instance, ensuring that you specify a key pair. If this is an instance that you have been using but you no longer have the .pem file for your key pair, you can replace the key pair with a new one. For more information, see I've lost my private key. How can I connect to my Linux instance?.

If you generated your own key pair, ensure that your key generator is set up to create RSA keys. DSA keys are not accepted.

If you get a Permission denied (publickey) error and none of the above applies (for example, you were able to connect previously), the permissions on the home directory of your instance may have been changed. Permissions for /home/instance-user-name/.ssh/authorized_keys must be limited to the owner only.

To verify the permissions on your instance
  1. Stop your instance and detach the root volume. For more information, see Stop and start your instance.

  2. Launch a temporary instance in the same Availability Zone as your current instance (use a similar or the same AMI as you used for your current instance), and attach the root volume to the temporary instance.

  3. Connect to the temporary instance, create a mount point, and mount the volume that you attached.

  4. From the temporary instance, check the permissions of the /home/instance-user-name/ directory of the attached volume. If necessary, adjust the permissions as follows:

    [ec2-user ~]$ chmod 600 mount_point/home/instance-user-name/.ssh/authorized_keys
    [ec2-user ~]$ chmod 700 mount_point/home/instance-user-name/.ssh
    [ec2-user ~]$ chmod 700 mount_point/home/instance-user-name
  5. Unmount the volume, detach it from the temporary instance, and re-attach it to the original instance. Ensure that you specify the correct device name for the root volume; for example, /dev/xvda.

  6. Start your instance. If you no longer require the temporary instance, you can terminate it.

Error: Unprotected private key file

Your private key file must be protected from read and write operations from any other users. If your private key can be read or written to by anyone but you, then SSH ignores your key and you see the following warning message below.

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: UNPROTECTED PRIVATE KEY FILE! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Permissions 0777 for '.ssh/my_private_key.pem' are too open. It is required that your private key files are NOT accessible by others. This private key will be ignored. bad permissions: ignore key: .ssh/my_private_key.pem Permission denied (publickey).

If you see a similar message when you try to log in to your instance, examine the first line of the error message to verify that you are using the correct public key for your instance. The above example uses the private key .ssh/my_private_key.pem with file permissions of 0777, which allow anyone to read or write to this file. This permission level is very insecure, and so SSH ignores this key.

If you are connecting from macOS or Linux, run the following command to fix this error, substituting the path for your private key file.

[ec2-user ~]$ chmod 0400 .ssh/my_private_key.pem

If you are connecting from Windows, perform the following steps on your local computer.

  1. Navigate to your .pem file.

  2. Right-click on the .pem file and select Properties.

  3. Choose the Security tab.

  4. Select Advanced.

  5. Verify that you are the owner of the file. If not, change the owner to your username.

  6. Select Disable inheritance and Remove all inherited permissions from this object.

  7. Select Add, Select a principal, enter your username, and select OK.

  8. From the Permission Entry window, grant Read permissions and select OK.

  9. Click Apply to ensure all settings are saved.

  10. Select OK to close the Advanced Security Settings window.

  11. Select OK to close the Properties window.

  12. You should be able to connect to your Linux instance from Windows via SSH.

From a Windows command prompt, run the following commands.

  1. From the command prompt, navigate to the file path location of your .pem file.

  2. Run the following command to reset and remove explicit permissions:

    icacls.exe $path /reset
  3. Run the following command to grant Read permissions to the current user:

    icacls.exe $path /GRANT:R "$($env:USERNAME):(R)"
  4. Run the following command to disable inheritance and remove inherited permissions.

    icacls.exe $path /inheritance:r
  5. You should be able to connect to your Linux instance from Windows via SSH.

Error: Private key must begin with "-----BEGIN RSA PRIVATE KEY-----" and end with "-----END RSA PRIVATE KEY-----"

If you use a third-party tool, such as ssh-keygen, to create an RSA key pair, it generates the private key in the OpenSSH key format. When you connect to your instance, if you use the private key in the OpenSSH format to decrypt the password, you'll get the error Private key must begin with "-----BEGIN RSA PRIVATE KEY-----" and end with "-----END RSA PRIVATE KEY-----".

To resolve the error, the private key must be in the PEM format. Use the following command to create the private key in the PEM format:

ssh-keygen -m PEM

Error: Server refused our key or No supported authentication methods available

If you use PuTTY to connect to your instance and get either of the following errors, Error: Server refused our key or Error: No supported authentication methods available, verify that you are connecting with the appropriate user name for your AMI. Type the user name in User name in the PuTTY Configuration window.

The appropriate user names are as follows:

AMI used to launch instance Default username

AL2023

Amazon Linux 2

Amazon Linux

ec2-user
CentOS centos or ec2-user
Debian admin
Fedora fedora or ec2-user
RHEL ec2-user or root
SUSE ec2-user or root
Ubuntu ubuntu
Oracle ec2-user
Bitnami bitnami
Rocky Linux rocky
Other Check with the AMI provider

You should also verify that:

Cannot ping instance

The ping command is a type of ICMP traffic — if you are unable to ping your instance, ensure that your inbound security group rules allow ICMP traffic for the Echo Request message from all sources, or from the computer or instance from which you are issuing the command.

If you are unable to issue a ping command from your instance, ensure that your outbound security group rules allow ICMP traffic for the Echo Request message to all destinations, or to the host that you are attempting to ping.

Ping commands can also be blocked by a firewall or time out due to network latency or hardware issues. You should consult your local network or system administrator for help with further troubleshooting.

Error: Server unexpectedly closed network connection

If you are connecting to your instance with PuTTY and you receive the error "Server unexpectedly closed network connection," verify that you have enabled keepalives on the Connection page of the PuTTY Configuration to avoid being disconnected. Some servers disconnect clients when they do not receive any data within a specified period of time. Set the Seconds between keepalives to 59 seconds.

If you still experience issues after enabling keepalives, try to disable Nagle's algorithm on the Connection page of the PuTTY Configuration.

Error: Host key validation failed for EC2 Instance Connect

If you rotate your instance host keys, the new host keys are not automatically uploaded to the Amazon trusted host keys database. This causes host key validation to fail when you try to connect to your instance using the EC2 Instance Connect browser-based client, and you're unable to connect to your instance.

To resolve the error, you must run the eic_harvest_hostkeys script on your instance, which uploads your new host key to EC2 Instance Connect. The script is located at /opt/aws/bin/ on Amazon Linux 2 instances, and at /usr/share/ec2-instance-connect/ on Ubuntu instances.

Amazon Linux 2
To resolve the host key validation failed error on an Amazon Linux 2 instance
  1. Connect to your instance using SSH.

    You can connect by using the EC2 Instance Connect CLI or by using the SSH key pair that was assigned to your instance when you launched it and the default user name of the AMI that you used to launch your instance. For Amazon Linux 2, the default user name is ec2-user.

    For example, if your instance was launched using Amazon Linux 2, your instance's public DNS name is ec2-a-b-c-d.us-west-2.compute.amazonaws.com, and the key pair is my_ec2_private_key.pem, use the following command to SSH into your instance:

    $ ssh -i my_ec2_private_key.pem ec2-user@ec2-a-b-c-d.us-west-2.compute.amazonaws.com

    For more information about connecting to your instance, see Connect to your Linux instance from Linux or macOS using SSH.

  2. Navigate to the following folder.

    [ec2-user ~]$ cd /opt/aws/bin/
  3. Run the following command on your instance.


    [ec2-user ~]$ ./eic_harvest_hostkeys

    Note that a successful call results in no output.

    You can now use the EC2 Instance Connect browser-based client to connect to your instance.

Ubuntu
To resolve the host key validation failed error on an Ubuntu instance
  1. Connect to your instance using SSH.

    You can connect by using the EC2 Instance Connect CLI or by using the SSH key pair that was assigned to your instance when you launched it and the default user name of the AMI that you used to launch your instance. For Ubuntu, the default user name is ubuntu.

    For example, if your instance was launched using Ubuntu, your instance's public DNS name is ec2-a-b-c-d.us-west-2.compute.amazonaws.com, and the key pair is my_ec2_private_key.pem, use the following command to SSH into your instance:

    $ ssh -i my_ec2_private_key.pem ubuntu@ec2-a-b-c-d.us-west-2.compute.amazonaws.com

    For more information about connecting to your instance, see Connect to your Linux instance from Linux or macOS using SSH.

  2. Navigate to the following folder.

    [ec2-user ~]$ cd /usr/share/ec2-instance-connect/
  3. Run the following command on your instance.


    [ec2-user ~]$ ./eic_harvest_hostkeys

    Note that a successful call results in no output.

    You can now use the EC2 Instance Connect browser-based client to connect to your instance.

Can't connect to Ubuntu instance using EC2 Instance Connect

If you use EC2 Instance Connect to connect to your Ubuntu instance and you get an error when attempting to connect, you can use the following information to try to fix the issue.

Possible cause

The ec2-instance-connect package on the instance is not the latest version.

Solution

Update the ec2-instance-connect package on the instance to the latest version, as follows:

  1. Connect to your instance using a method other than EC2 Instance Connect.

  2. Run the following command on your instance to update the ec2-instance-connect package to the latest version.

    apt update && apt upgrade

I've lost my private key. How can I connect to my Linux instance?

If you lose the private key for an EBS-backed instance, you can regain access to your instance. You must stop the instance, detach its root volume and attach it to another instance as a data volume, modify the authorized_keys file with a new public key, move the volume back to the original instance, and restart the instance. For more information about launching, connecting to, and stopping instances, see Instance lifecycle.

This procedure is only supported for instances with EBS root volumes. If the root device is an instance store volume, you cannot use this procedure to regain access to your instance; you must have the private key to connect to the instance. To determine the root device type of your instance, open the Amazon EC2 console, choose Instances, select the instance, choose the Storage tab, and in the Root device details section, check the value of Root device type.

The value is either EBS or INSTANCE-STORE.

In addition to the following steps, there are other ways to connect to your Linux instance if you lose your private key. For more information, see How can I connect to my Amazon EC2 instance if I lost my SSH key pair after its initial launch?

Step 1: Create a new key pair

Create a new key pair using either the Amazon EC2 console or a third-party tool. If you want to name your new key pair exactly the same as the lost private key, you must first delete the existing key pair. For information about creating a new key pair, see Create a key pair using Amazon EC2 or Create a key pair using a third-party tool and import the public key to Amazon EC2.

Step 2: Get information about the original instance and its root volume

Make note of the following information because you'll need it to complete this procedure.

To get information about your original instance
  1. Open the Amazon EC2 console at https://console.amazonaws.cn/ec2/.

  2. Choose Instances in the navigation pane, and then select the instance that you'd like to connect to. (We'll refer to this as the original instance.)

  3. On the Details tab, make note of the instance ID and AMI ID.

  4. On the Networking tab, make note of the Availability Zone.

  5. On the Storage tab, under Root device name, make note of the device name for the root volume (for example, /dev/xvda). Then, under Block devices, find this device name and make note of the volume ID (for example, vol-0a1234b5678c910de).

Step 3: Stop the original instance

Choose Instance state, Stop instance. If this option is disabled, either the instance is already stopped or its root device is an instance store volume.

Warning

When you stop an instance, the data on any instance store volumes is erased. To keep data from instance store volumes, be sure to back it up to persistent storage.

Step 4: Launch a temporary instance

New console
To launch a temporary instance
  1. In the navigation pane, choose Instances, and then choose Launch instances.

  2. In the Name and tags section, for Name, enter Temporary.

  3. In the Application and OS Images section, select the same AMI that you used to launch the original instance. If this AMI is unavailable, you can create an AMI that you can use from the stopped instance. For more information, see Create an Amazon EBS-backed Linux AMI .

  4. In the Instance type section, keep the default instance type.

  5. In the Key pair section, for Key pair name, select the existing key pair to use or create a new one.

  6. In the Network settings section, choose Edit, and then for Subnet, select a subnet in the same Availability Zone as the original instance.

  7. In the Summary panel, choose Launch.

Old console

Choose Launch instances, and then use the launch wizard to launch a temporary instance with the following options:

  • On the Choose an AMI page, select the same AMI that you used to launch the original instance. If this AMI is unavailable, you can create an AMI that you can use from the stopped instance. For more information, see Create an Amazon EBS-backed Linux AMI.

  • On the Choose an Instance Type page, leave the default instance type that the wizard selects for you.

  • On the Configure Instance Details page, specify the same Availability Zone as the original instance. If you're launching an instance in a VPC, select a subnet in this Availability Zone.

  • On the Add Tags page, add the tag Name=Temporary to the instance to indicate that this is a temporary instance.

  • On the Review page, choose Launch. Choose the key pair that you created in Step 1, then choose Launch Instances.

Step 5: Detach the root volume from the original instance and attach it to the temporary instance

  1. In the navigation pane, choose Volumes and select the root device volume for the original instance (you made note of its volume ID in a previous step). Choose Actions, Detach volume, and then choose Detach. Wait for the state of the volume to become available. (You might need to choose the Refresh icon.)

  2. With the volume still selected, choose Actions, and then choose Attach volume. Select the instance ID of the temporary instance, make note of the device name specified under Device name (for example, /dev/sdf), and then choose Attach volume.

    Note

    If you launched your original instance from an Amazon Web Services Marketplace AMI and your volume contains Amazon Web Services Marketplace codes, you must first stop the temporary instance before you can attach the volume.

Step 6: Add the new public key to authorized_keys on the original volume mounted to the temporary instance

  1. Connect to the temporary instance.

  2. From the temporary instance, mount the volume that you attached to the instance so that you can access its file system. For example, if the device name is /dev/sdf, use the following commands to mount the volume as /mnt/tempvol.

    Note

    The device name might appear differently on your instance. For example, devices mounted as /dev/sdf might show up as /dev/xvdf on the instance. Some versions of Red Hat (or its variants, such as CentOS) might even increment the trailing letter by 4 characters, where /dev/sdf becomes /dev/xvdk.

    1. Use the lsblk command to determine if the volume is partitioned.

      [ec2-user ~]$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT xvda 202:0 0 8G 0 disk └─xvda1 202:1 0 8G 0 part / xvdf 202:80 0 101G 0 disk └─xvdf1 202:81 0 101G 0 part xvdg 202:96 0 30G 0 disk

      In the preceding example, /dev/xvda and /dev/xvdf are partitioned volumes, and /dev/xvdg is not. If your volume is partitioned, you mount the partition (/dev/xvdf1) instead of the raw device (/dev/xvdf) in the next steps.

    2. Create a temporary directory to mount the volume.

      [ec2-user ~]$ sudo mkdir /mnt/tempvol
    3. Mount the volume (or partition) at the temporary mount point, using the volume name or device name that you identified earlier. The required command depends on your operating system's file system. Note that the device name might appear differently on your instance. See the note in Step 6 for more information.

      • Amazon Linux, Ubuntu, and Debian

        [ec2-user ~]$ sudo mount /dev/xvdf1 /mnt/tempvol
      • Amazon Linux 2, CentOS, SUSE Linux 12, and RHEL 7.x

        [ec2-user ~]$ sudo mount -o nouuid /dev/xvdf1 /mnt/tempvol
    Note

    If you get an error stating that the file system is corrupt, run the following command to use the fsck utility to check the file system and repair any issues:

    [ec2-user ~]$ sudo fsck /dev/xvdf1
  3. From the temporary instance, use the following command to update authorized_keys on the mounted volume with the new public key from the authorized_keys for the temporary instance.

    Important

    The following examples use the Amazon Linux user name ec2-user. You might need to substitute a different user name, such as ubuntu for Ubuntu instances.

    [ec2-user ~]$ cp .ssh/authorized_keys /mnt/tempvol/home/ec2-user/.ssh/authorized_keys

    If this copy succeeded, you can go to the next step.

    (Optional) Otherwise, if you don't have permission to edit files in /mnt/tempvol, you must update the file using sudo and then check the permissions on the file to verify that you are able to log into the original instance. Use the following command to check the permissions on the file.

    [ec2-user ~]$ sudo ls -l /mnt/tempvol/home/ec2-user/.ssh total 4 -rw------- 1 222 500 398 Sep 13 22:54 authorized_keys

    In this example output, 222 is the user ID and 500 is the group ID. Next, use sudo to re-run the copy command that failed.

    [ec2-user ~]$ sudo cp .ssh/authorized_keys /mnt/tempvol/home/ec2-user/.ssh/authorized_keys

    Run the following command again to determine whether the permissions changed.

    [ec2-user ~]$ sudo ls -l /mnt/tempvol/home/ec2-user/.ssh

    If the user ID and group ID have changed, use the following command to restore them.

    [ec2-user ~]$ sudo chown 222:500 /mnt/tempvol/home/ec2-user/.ssh/authorized_keys

Step 7: Unmount and detach the original volume from the temporary instance, and reattach it to the original instance

  1. From the temporary instance, unmount the volume that you attached so that you can reattach it to the original instance. For example, use the following command to unmount the volume at /mnt/tempvol.

    [ec2-user ~]$ sudo umount /mnt/tempvol
  2. Detach the volume from the temporary instance (you unmounted it in the previous step): From the Amazon EC2 console, choose Volumes in the navigation pane, select the root device volume for the original instance (you made note of the volume ID in a previous step), choose Actions, Detach volume, and then choose Detach. Wait for the state of the volume to become available. (You might need to choose the Refresh icon.)

  3. Reattach the volume to the original instance: With the volume still selected, choose Actions, Attach volume. Select the instance ID of the original instance, specify the device name that you noted earlier in Step 2 for the original root device attachment (/dev/sda1 or /dev/xvda), and then choose Attach volume.

    Important

    If you don't specify the same device name as the original attachment, you cannot start the original instance. Amazon EC2 expects the root device volume at sda1 or /dev/xvda.

Step 8: Connect to the original instance using the new key pair

Select the original instance, choose Instance state, Start instance. After the instance enters the running state, you can connect to it using the private key file for your new key pair.

Note

If the name of your new key pair and corresponding private key file is different from the name of the original key pair, ensure that you specify the name of the new private key file when you connect to your instance.

Step 9: Clean up

(Optional) You can terminate the temporary instance if you have no further use for it. Select the temporary instance, and choose Instance state, Terminate instance.