maint: Do not xz-compress ISO images.

The xz-compressed image is 23% smaller than the original ISO image (with
built-in zlib compression), but the extra decompression step is
unconventional and often a hindrance for users.  See discussion at
<https://lists.gnu.org/archive/html/guix-devel/2021-04/msg00497.html>.

* Makefile.am (release): Do not compress ISO images.
* doc/guix.texi (USB Stick and DVD Installation): Remove ".xz" suffix
from URL and file name.
(Copying to a USB Stick, Burning on a DVD): Remove introductory words,
@enumerate, and first item.

Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>

2 files changed, 6 insertions, 30 deletions

diff --git a/Makefile.am b/Makefile.am
index de32a0a42b..0a4bb13e5b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -886,9 +886,9 @@ release: dist-with-updated-version all
 	    echo "failed to produced Guix installation image for $$system" >&2 ;	\
 	    exit 1 ;									\
 	  fi ;										\
-	  xz < "$$image" > "$(releasedir)/$(GUIX_SYSTEM_IMAGE_BASE).$$system.iso.xz.tmp" ;	\
-	  mv "$(releasedir)/$(GUIX_SYSTEM_IMAGE_BASE).$$system.iso.xz.tmp"		\
-	     "$(releasedir)/$(GUIX_SYSTEM_IMAGE_BASE).$$system.iso.xz" ;		\
+	  cp "$$image" "$(releasedir)/$(GUIX_SYSTEM_IMAGE_BASE).$$system.iso.tmp" ;	\
+	  mv "$(releasedir)/$(GUIX_SYSTEM_IMAGE_BASE).$$system.iso.tmp"			\
+	     "$(releasedir)/$(GUIX_SYSTEM_IMAGE_BASE).$$system.iso" ;			\
 	done
 # Generate the VM images.
 	for system in $(GUIX_SYSTEM_VM_SYSTEMS) ; do					\
diff --git a/doc/guix.texi b/doc/guix.texi
index e23e831676..ff592ce364 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -2099,7 +2099,7 @@ about their support in GNU/Linux.
 
 An ISO-9660 installation image that can be written to a USB stick or
 burnt to a DVD can be downloaded from
-@indicateurl{@value{BASE-URL}/guix-system-install-@value{VERSION}.x86_64-linux.iso.xz},
+@indicateurl{@value{BASE-URL}/guix-system-install-@value{VERSION}.x86_64-linux.iso},
 where you can replace @code{x86_64-linux} with one of:
 
 @table @code
@@ -2115,8 +2115,8 @@ Make sure to download the associated @file{.sig} file and to verify the
 authenticity of the image against it, along these lines:
 
 @example
-$ wget @value{BASE-URL}/guix-system-install-@value{VERSION}.x86_64-linux.iso.xz.sig
-$ gpg --verify guix-system-install-@value{VERSION}.x86_64-linux.iso.xz.sig
+$ wget @value{BASE-URL}/guix-system-install-@value{VERSION}.x86_64-linux.iso.sig
+$ gpg --verify guix-system-install-@value{VERSION}.x86_64-linux.iso.sig
 @end example
 
 If that command fails because you do not have the required public key,
@@ -2140,17 +2140,6 @@ It is meant to be copied @emph{as is} to a large-enough USB stick or DVD.
 
 @unnumberedsubsec Copying to a USB Stick
 
-To copy the image to a USB stick, follow these steps:
-
-@enumerate
-@item
-Decompress the image using the @command{xz} command:
-
-@example
-xz -d guix-system-install-@value{VERSION}.x86_64-linux.iso.xz
-@end example
-
-@item
 Insert a USB stick of 1@tie{}GiB or more into your machine, and determine
 its device name.  Assuming that the USB stick is known as @file{/dev/sdX},
 copy the image with:
@@ -2161,21 +2150,9 @@ sync
 @end example
 
 Access to @file{/dev/sdX} usually requires root privileges.
-@end enumerate
 
 @unnumberedsubsec Burning on a DVD
 
-To copy the image to a DVD, follow these steps:
-
-@enumerate
-@item
-Decompress the image using the @command{xz} command:
-
-@example
-xz -d guix-system-install-@value{VERSION}.x86_64-linux.iso.xz
-@end example
-
-@item
 Insert a blank DVD into your machine, and determine
 its device name.  Assuming that the DVD drive is known as @file{/dev/srX},
 copy the image with:
@@ -2185,7 +2162,6 @@ growisofs -dvd-compat -Z /dev/srX=guix-system-install-@value{VERSION}.x86_64-lin
 @end example
 
 Access to @file{/dev/srX} usually requires root privileges.
-@end enumerate
 
 @unnumberedsubsec Booting