Resize AWS root ebs volume

[richard....@wealthwizards.com]

Hi,

Really sorry to be asking this because I can see there are previous threads, e.g. "Configuring size of root volume on EC2" but they actually don't provide a clear answer and neither do the docs.

I'm building an AMI using the amazon-ebs builder. The reference AMI is a Debian stretch image with an 8GB root volume. The source images use /dev/xvda1 as the root partition.

I'd like my packer image to have a much larger volume, e.g. 40GB. Previous threads indicate this should be possible by adding:

        "ami_block_device_mappings": [ {
            "device_name": "/dev/xvda",
            "volume_size": 40,
            "delete_on_termination": true
        } ],
        "launch_block_device_mappings": [ {
            "device_name": "/dev/xvda",
            "volume_size": 40,
            "delete_on_termination": true
        } ]

It's not clear to me what the distinction between  ami_block_device_mappings and launch_block_device_mappings is. What what I understand of the docs they should be used when I want to add additional devices beyond the root vol, but the discussion in the other thread suggests using the code above is used to modify the root volume size.

I don't fully understand what it's doing, but more to the point, I can't make it work.

The reference image boots from /dev/xvda1, so presumably I need 

"device_name": "/dev/xvda"

but that throws this error:

The device 'xvda' is used in more than one block-device mapping

So, what device should I use is the source AMI is using /dev/xvda1 as root partition and what the difference between the two mappings?

(I know I may need to deal with fs resize, but I'll get to that when it's a problem)

Many Thanks,

Rich

[Rickard von Essen]

Setting this in ami_block_device_mappings makes your custom AMI come with a 40 GB root device but the instance launched by packer has the standard 8 GB. Example:

[...]

    amazon-ebs: Debian GNU/Linux 8 (jessie)

    amazon-ebs: Filesystem      Size  Used Avail Use% Mounted on    [df -h]

    amazon-ebs: /dev/xvda2      7.8G  819M  6.6G  11% /

    amazon-ebs: udev             10M     0   10M   0% /dev

    amazon-ebs: tmpfs           200M  4.2M  196M   3% /run

    amazon-ebs: tmpfs           500M     0  500M   0% /dev/shm

    amazon-ebs: tmpfs           5.0M     0  5.0M   0% /run/lock

    amazon-ebs: tmpfs           500M     0  500M   0% /sys/fs/cgroup

    amazon-ebs: NAME    MAJ:MIN RM    SIZE RO TYPE MOUNTPOINT     [lsblk]

    amazon-ebs: xvda    202:0    0      8G  0 disk

    amazon-ebs: ├─xvda1 202:1    0 1007.5K  0 part

    amazon-ebs: └─xvda2 202:2    0      8G  0 part /

[...]

aws ec2 describe-images --image-ids <ami-id> --query 'Images[0].BlockDeviceMappings[0]'

{

    "DeviceName": "/dev/xvda",

    "Ebs": {

        "Encrypted": false,

        "DeleteOnTermination": true,

        "VolumeType": "standard",

        "VolumeSize": 40,

        "SnapshotId": "snap-04aa234cd2128d60a"

    }

}

While setting this in launch_block_device_mappins changes the device also for the instance packer launches for provisioning and since that is what is captured in your custom AMI that will have 40 GB too.

Example:

[...]

    amazon-ebs: Debian GNU/Linux 8 (jessie)

    amazon-ebs: Filesystem      Size  Used Avail Use% Mounted on    [df -h]

    amazon-ebs: /dev/xvda2       40G  825M   37G   3% /

    amazon-ebs: udev             10M     0   10M   0% /dev

    amazon-ebs: tmpfs           200M  4.2M  196M   3% /run

    amazon-ebs: tmpfs           500M     0  500M   0% /dev/shm

    amazon-ebs: tmpfs           5.0M     0  5.0M   0% /run/lock

    amazon-ebs: tmpfs           500M     0  500M   0% /sys/fs/cgroup

    amazon-ebs: NAME    MAJ:MIN RM    SIZE RO TYPE MOUNTPOINT    [lsblk]

    amazon-ebs: xvda    202:0    0     40G  0 disk

    amazon-ebs: ├─xvda1 202:1    0 1007.5K  0 part

    amazon-ebs: └─xvda2 202:2    0     40G  0 part /

[...]

aws ec2 describe-images --image-ids <ami-id> --query 'Images[0].BlockDeviceMappings[0]'

{

    "DeviceName": "/dev/xvda",

    "Ebs": {

        "Encrypted": false,

        "DeleteOnTermination": true,

        "VolumeType": "standard",

        "VolumeSize": 40,

        "SnapshotId": "snap-0132901385c9a556d"

    }

}

Hope that makes it clear.

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[richard....@wealthwizards.com]

Hi Rickard,

Thanks for the response, that helps make the distinction clear. What I'm still blocked on is getting the root vol to be increased.

The source image boots from /dev/xvda(1). When I specify /dev/xvda as the device in ami_block_device_mappings

This builder config:

"builders": [{

     "type": "amazon-ebs",
     "communicator": "ssh",
     "ssh_pty": "true",
     "access_key": "{{user `aws_access_key`}}",
     "secret_key": "{{user `aws_secret_key`}}",
     "region": "eu-west-1",
     "source_ami": "ami-88e60ff1",
     "instance_type": "t2.nano",
     "ssh_username": "admin",
     "ami_name": "jenkins-slave-stretch{{timestamp}}",
     "encrypt_boot": true,
     "ami_block_device_mappings": [ {
         "device_name": "/dev/xvda",
         "volume_size": 42,
         "volume_type": "gp2",
         "encrypted": true,
         "delete_on_termination": true
     } ]
   }],

It fails with the error:

Error creating AMI: InvalidBlockDeviceMapping: The device 'xvda' is used in more than one block-device mapping

If I specify a different device id then I end up with an additional disk on the image:

This builder config:

 

 "builders": [{

     "type": "amazon-ebs",
     "communicator": "ssh",
     "ssh_pty": "true",
     "access_key": "{{user `aws_access_key`}}",
     "secret_key": "{{user `aws_secret_key`}}",
     "region": "eu-west-1",
     "source_ami": "ami-88e60ff1",
     "instance_type": "t2.nano",
     "ssh_username": "admin",
     "ami_name": "jenkins-slave-stretch{{timestamp}}",
     "encrypt_boot": true,
     "ami_block_device_mappings": [ {
         "device_name": "/dev/xvdb",
         "volume_size": 42,
         "volume_type": "gp2",
         "encrypted": true,
         "delete_on_termination": true
     } ]
   }],

Ends up like this:

So I've so-far failed to extend the root volume of the ami produced by packer. What am I doing wrong?

Thanks again!

Rich

[Rickard von Essen]

You can't set encrypted to true to a existing device. Try remove that and I guess it should work. If you want to encrypt it use encrypt_boot: true.

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[richard....@wealthwizards.com]

Hi,

Ok, so I've tried removing the encrypt options but still no joy:

   "builders": [{
     "type": "amazon-ebs",
     "communicator": "ssh",
     "ssh_pty": "true",
     "access_key": "{{user `aws_access_key`}}",
     "secret_key": "{{user `aws_secret_key`}}",
     "region": "eu-west-1",
     "source_ami": "ami-88e60ff1",
     "instance_type": "t2.nano",
     "ssh_username": "admin",
     "ami_name": "jenkins-slave-stretch{{timestamp}}",

     "ami_block_device_mappings": [ {
         "device_name": "/dev/xvda",
         "volume_size": 42,
         "volume_type": "gp2",

         "delete_on_termination": true
     } ]
   }],

Gives:

Build 'amazon-ebs' errored: Error creating AMI: InvalidBlockDeviceMapping: The device 'xvda' is used in more than one block-device mapping

status code: 400, request id: 93848ef4-ad21-4c5f-aa35-29c66c545a6a

I tried both with and without  "encrypt_boot": true, in case that made any difference, but it didn't change either way.

Thanks again,

Rich

[richard....@wealthwizards.com]

Hey, thanks

I tried that too but it just creates an additional device on the system, it doesn't alter the existing block device. :(

Regards

Rich

On Friday, August 18, 2017 at 3:16:08 PM UTC+1, Daniel Berard wrote:

Try using xvdf. xvda is the default device. 

[richard....@wealthwizards.com]

w00t w00t!!

finally got it working, thanks to all that helped. 

the working config is:

   "builders": [{

     "type": "amazon-ebs",

     "communicator": "ssh",

     "ssh_pty": "true",

     "access_key": "{{user `aws_access_key`}}",

     "secret_key": "{{user `aws_secret_key`}}",

     "region": "eu-west-1",

     "source_ami": "ami-88e60ff1",

     "instance_type": "t2.nano",

     "ssh_username": "admin",

     "ami_name": "jenkins-slave-stretch{{timestamp}}",

     "encrypt_boot": true,

     "ami_block_device_mappings": [ {

         "device_name": "xvda",

         "volume_size": 42,

         "volume_type": "gp2",

         "delete_on_termination": true

     } ]

   }],

The important bit is that while the source image uses /dev/xvda as the boot image the device name specified is "xvda". I don't know why this distinction is needed, but it works. 

[ME2Digital]

Hi all.

I have the same problem with packer 1.0.4

I use the following json

###
    "ami_block_device_mappings": [
    {
      "delete_on_termination": false,
      "device_name": "/dev/xvda",
      "volume_size": "25",
      "volume_type": "gp2"
    }
    ],
##

Full json: https://gist.github.com/git001/be7f0293bc16aac3a80801da2ffef1ac

with this provision.sh https://gist.github.com/git001/ae972d1884fd365f9ebbfc323c114476

I have tried several variants of "device_name"

"device_name": "/dev/xvda",
"device_name": "/dev/sda",
"device_name": "xvda",

None of them increase the size of the atomic root device.

Please can someone shade some light on this, thanks.

You can find the output of a packer run here https://gist.github.com/git001/a0e95d80763ffbec58aa9b4898b5cfe0

thanks for help.

Regards
Aleks

Am Donnerstag, 17. August 2017 23:49:06 UTC+2 schrieb richard....@wealthwizards.com:

Hi,

Really sorry to be asking this because I can see there are previous threads, e.g. "Configuring size of root volume on EC2" but they actually don't provide a clear answer and neither do the docs.

I'm building an AMI using the amazon-ebs builder. The reference AMI is a Debian stretch image with an 8GB root volume. The source images use /dev/xvda1 as the root partition.

[snipp]

[Rickard von Essen]

Since you are running expansion of the fs at provisioning you should probably just switch to lunch_block_device_mappings.

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[ME2Digital]

Am Dienstag, 22. August 2017 11:46:05 UTC+2 schrieb Rickard von Essen:

Since you are running expansion of the fs at provisioning you should probably just switch to lunch_block_device_mappings.

Thanks. I have now used the following config and this works.

###

    "launch_block_device_mappings": [
    {
      "delete_on_termination": false,
      "device_name": "/dev/sda1",
      "volume_size": 150,
      "volume_type": "gp2"
    }
    ],

###

 

Thanks for help

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[Samvitha K]

Once you expand the root disk i.e. /dev/xvda to desired size, may i know how to create custom filesystem partitions (/var, /home/, /var/log etc) on a AWS EBS disk during boot process using hashicorp packer? Is it possible and did anyone try this?

[Megan Marsh]

I believe that kind of custom partitioning has to happen as part of your provisioning scripts. Packer won't do it for you.

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[Samvitha K]

The provisioner will come to rescue once the system boots but as i want to accomplish the custom partitions during the build process, i would like to know how to achieve this. the reason i am asking this is, many organizations doesnt want to have all filesystems under / and more over CIS benchmarks expects to have separate filesystems, so i would like to know how is this being actioned.

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[Megan Marsh]

If it can be done using the block device mappings https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_BlockDeviceMapping.html then you can configure it in Packer. Otherwise, you have to do it yourself via provisioning scripts.