website: Updated image URLs to img.gz

In efforts to reduce storage costs, gem5 images have been gzipped. URLs
in the website have therefore been updated accordingly.

We've also added the .img extension to make it clearer as to what what
these files are.

Change-Id: I062e6e42c8aa578c95817c7a100869051f634985
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/35120
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: Jason Lowe-Power <power.jg@gmail.com>
diff --git a/_pages/documentation/general_docs/gem5_resources.md b/_pages/documentation/general_docs/gem5_resources.md
index 520c357..c03dbf5 100644
--- a/_pages/documentation/general_docs/gem5_resources.md
+++ b/_pages/documentation/general_docs/gem5_resources.md
@@ -43,10 +43,10 @@
 |square | --- | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/square) |
 |spec-2006 | --- | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/spec-2017) |
 |spec-2017 | --- | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/spec-2006) |
-|gapbs | [Disk Image](http://dist.gem5.org/dist/v20/images/x86/ubuntu-18-04/gapbs) | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/gapbs) |
-|parsec | [Disk Image](http://dist.gem5.org/dist/v20/images/x86/ubuntu-18-04/parsec) | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/parsec) |
-|npb | [Disk Image](http://dist.gem5.org/dist/v20/images/x86/ubuntu-18-04/npb) | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/npb) |
-|Linux boot-exit | [Disk Image](http://dist.gem5.org/v20/images/x86/ubuntu-18-04/boot-exit) |[here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/boot-exit) |
+|gapbs | [Disk Image (GZIPPED)](http://dist.gem5.org/dist/v20/images/x86/ubuntu-18-04/gapbs.img.gz) | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/gapbs) |
+|parsec | [Disk Image (GZIPPED)](http://dist.gem5.org/dist/v20/images/x86/ubuntu-18-04/parsec.img.gz) | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/parsec) |
+|npb | [Disk Image (GZIPPED)](http://dist.gem5.org/dist/v20/images/x86/ubuntu-18-04/npb.img.gz) | [here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/npb) |
+|Linux boot-exit | [Disk Image (GZIPPED)](http://dist.gem5.org/v20/images/x86/ubuntu-18-04/boot-exit.img.gz) |[here](https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/master/src/boot-exit) |
 
 ## How do I obtain the gem5 resource sources?
 
diff --git a/_posts/2020-03-09-boot-tests.md b/_posts/2020-03-09-boot-tests.md
index a67265d..1ab3041 100644
--- a/_posts/2020-03-09-boot-tests.md
+++ b/_posts/2020-03-09-boot-tests.md
@@ -71,7 +71,7 @@
 The gem5 configuration scripts used to run these experiments are available in the [gem5art repo](https://github.com/darchr/gem5art/tree/master/docs/gem5-configs/configs-boot-tests/) and the details of how these experiments were run using gem5art can be found in the [gem5art boot tutorial](https://gem5art.readthedocs.io/en/latest/tutorials/boot-tutorial.html).
 The disk image and Linux kernel binaries we used are available from the following links (**warning:** the sizes of these files range from few MBs to 2GB):
 
-- [disk image](http://dist.gem5.org/dist/current/images/x86/ubuntu-18-04/base.img) (**Note:** /root/.bashrc in this disk image contains `m5 exit`, which will make the guest terminate the simulation as soon as it boots)
+- [disk image (GZIPPED)](http://dist.gem5.org/dist/current/images/x86/ubuntu-18-04/base.img.gz) (**Note:** /root/.bashrc in this disk image contains `m5 exit`, which will make the guest terminate the simulation as soon as it boots)
 - [vmlinux-4.4.186](http://dist.gem5.org/dist/current/kernels/x86/static/vmlinux-4.4.189)
 - [vmlinux-4.9.186](http://dist.gem5.org/dist/current/kernels/x86/static/vmlinux-4.9.186)
 - [vmlinux-4.14.134](http://dist.gem5.org/dist/current/kernels/x86/static/vmlinux-4.14.134)