builder/amazon: Added and corrected some default values in the docs.

website/source/docs/builders/amazon-chroot.html.md

@@ -107,11 +107,11 @@ each category, the available configuration keys are alphabetized.
     `{{.Command}}`. This may be useful to set if you want to set environmental
     variables or perhaps run it with `sudo` or so on. This is a configuration
     template where the `.Command` variable is replaced with the command to
-    be run.
+    be run. Defaults to "{{.Command}}".
 
 -   `copy_files` (array of strings) - Paths to files on the running EC2 instance
-    that will be copied into the chroot environment prior to provisioning. This
-    is useful, for example, to copy `/etc/resolv.conf` so that DNS lookups work.
+    that will be copied into the chroot environment prior to provisioning. Defaults
+    to `/etc/resolv.conf` so that DNS lookups work.
 
 -   `device_path` (string) - The path to the device where the root volume of the
     source AMI will be attached. This defaults to "" (empty string), which
@@ -139,7 +139,7 @@ each category, the available configuration keys are alphabetized.
 
 -   `mount_path` (string) - The path where the volume will be mounted. This is
     where the chroot environment will be. This defaults to
-    `packer-amazon-chroot-volumes/{{.Device}}`. This is a configuration template
+    `/mnt/packer-amazon-chroot-volumes/{{.Device}}`. This is a configuration template
     where the `.Device` variable is replaced with the name of the device where
     the volume is attached.
 

website/source/docs/builders/amazon-instance.html.md

@@ -239,7 +239,8 @@ builder.
 -   `x509_upload_path` (string) - The path on the remote machine where the X509
     certificate will be uploaded. This path must already exist and be writable.
     X509 certificates are uploaded after provisioning is run, so it is perfectly
-    okay to create this directory as part of the provisioning process.
+    okay to create this directory as part of the provisioning process. Defaults to
+    `/tmp`.
 
 -   `windows_password_timeout` (string) - The timeout for waiting for a Windows
     password for Windows instances. Defaults to 20 minutes. Example value: "10m"
@@ -327,8 +328,9 @@ include those files (see the `--no-filter` option of ec2-bundle-vol).
 ### Bundle Upload Command
 
 The default value for `bundle_upload_command` is shown below. It is split across
-multiple lines for convenience of reading. The bundle upload command is
-responsible for taking the bundled volume and uploading it to S3.
+multiple lines for convenience of reading. Access key and secret key are omitted
+if using instance profile. The bundle upload command is responsible for taking
+the bundled volume and uploading it to S3.
 
 ``` {.text}
 sudo -i -n ec2-upload-bundle \