[arch-releng] [PATCH] archiso_loop_mnt - cleaner boot from loopmounted iso file

Sat Jul 18 12:18:10 UTC 2015

On 07/13/2015 04:19 AM, Gerardo Exequiel Pozzi wrote:
> On 07/12/2015 09:19 AM, Adam Purkrt wrote:
>> On 07/12/2015 02:29 AM, Gerardo Exequiel Pozzi wrote:
>>> On 07/11/2015 04:00 PM, Adam Purkrt wrote:
>>>> I would like to suggest the patch below, to archiso_loop_mnt hook.
>>>>
>>>> Currently, when booting loopmounted iso file, it is necessary to
>>>> specify not only img_dev and img_loop (which should be sufficient),
>>>> but also archisolabel or archisodevice. With the patch, archisodevice
>>>> is directly populated with the correct loop device, and it is not
>>>> necessary to specify the label when booting from loopmounted iso,
>>>> which makes for leaner and cleaner grub.cfg.
>>>>
>>>> The kernel command line in grub.cfg currently needed:
>>>>
>>>> linux (loop)/arch/boot/x86_64/vmlinuz archisolabel=ARCH_201507
>>>> img_dev=$imgdevpath img_loop=$isofile earlymodules=loop
>>>>
>>>> after the patch:
>>>>
>>>> linux (loop)/arch/boot/x86_64/vmlinuz img_dev=$imgdevpath
>>>> img_loop=$isofile earlymodules=loop
>>>>
>>> You are right!
>>>
>>> Please also update the README.altbootmethods ;)
>>>
>>> PS: "earlymodules=loop": Is like a copy&paste hurricane from old age.
>>> It was a temporal workaround (2011.08.19), but spread across all places.
>>>
>>> Thanks.
>>>
>>
>> It's good that "earlymodules=loop" is not necessary, thanks for pointing it out.
>>
>> Updated the README.altbootmethods, using uuid over label. Overall the patch is:
>>
>> diff --git a/archiso/initcpio/hooks/archiso_loop_mnt b/archiso/initcpio/hooks/archiso_loop_mnt
>> index 46338e5..f95a47d 100644
>> --- a/archiso/initcpio/hooks/archiso_loop_mnt
>> +++ b/archiso/initcpio/hooks/archiso_loop_mnt
>> @@ -18,7 +18,9 @@ archiso_loop_mount_handler () {
>> echo $(readlink -f ${img_dev}) >> /run/archiso/used_block_devices
>> fi
>> 
>> - if ! _dev_loop=$(losetup --find --show --read-only "/run/archiso/img_dev/${img_loop}"); then
>> + if _dev_loop=$(losetup --find --show --read-only "/run/archiso/img_dev/${img_loop}"); then
>> + archisodevice="${_dev_loop}"
>> + else
>> echo "ERROR: Setting loopback device for file '/run/archiso/img_dev/${img_loop}'"
>> launch_interactive_shell
>> fi
>> diff --git a/docs/README.altbootmethods b/docs/README.altbootmethods
>> index 3c07e03..cbfada4 100644
>> --- a/docs/README.altbootmethods
>> +++ b/docs/README.altbootmethods
>> @@ -25,20 +25,23 @@ Where:
>> 
>> Note: Described method is for using with GRUB2.
>> GRUB2 is installed on target media and archlinux-<YYYY>.<MM>.<DD>-dual.iso
>> - is at path <TARGET-PATH> on disk <D> and partition ,
>> - where filesystem is labeled as <TARGET-FS-LABEL>.
>> + is at path <TARGET-PATH> on disk <D> and partition .
>> 
>> menuentry "Arch Linux (x86_64)" {
>> + set isopartition=hd<D>,
>> set isofile="/<TARGET-PATH>/archlinux-<YYYY>.<MM>.<DD>-dual.iso"
>> - loopback loop (hd<D>,)$isofile
>> - linux (loop)/arch/boot/x86_64/vmlinuz archisolabel=<FS-LABEL> img_label=<TARGET-FS-LABEL> img_loop=$isofile
>> + loopback loop ($isopartition)$isofile
>> + probe -u $isopartition --set=isouuid
>> + linux (loop)/arch/boot/x86_64/vmlinuz img_dev=/dev/disk/by-uuid/$isouuid img_loop=$isofile
>> initrd (loop)/arch/boot/x86_64/archiso.img
>> }
>> 
>> menuentry "Arch Linux (i686)" {
>> + set isopartition=hd<D>,
>> set isofile="/<TARGET-PATH>/archlinux-<YYYY>.<MM>.<DD>-dual.iso"
>> - loopback loop (hd<D>,)$isofile
>> - linux (loop)/arch/boot/i686/vmlinuz archisolabel=<FS-LABEL> img_label=<TARGET-FS-LABEL> img_loop=$isofile
>> + loopback loop ($isopartition)$isofile
>> + probe -u $isopartition --set=isouuid
>> + linux (loop)/arch/boot/i686/vmlinuz img_dev=/dev/disk/by-uuid/$isouuid img_loop=$isofile
>> initrd (loop)/arch/boot/i686/archiso.img
>> }
>> 
>>
>>
>>
>>
>>
>> One more thing - I would vote for deprecating "img_label" parameter and (sooner or later) removing it, i.e.
>>
>> /archiso/initcpio/hooks/archiso_loop_mnt
>> - [[ -n "${img_label}" ]] && img_dev="/dev/disk/by-label/${img_label}"
>>
>> /docs/README.bootparams
>> -* img_label= Set the filesystem label where archiso-image.iso.
>> - Default: (unset)
>> * img_dev= Device where archiso-image.iso reside.
>> - Default: (unset) or "/dev/disk/by-label/${img_label}"
>> + Default: (unset)
>>
>> since: 1) it is more reliable to refer to a partition by uuid
>> 2) there is no "img_uuid" - and I don't think there should be, "img_dev=/dev/disk/by-uuid/[uuid]" is perfectly fine
>> 3) it would be still possible to address by label using "img_dev=/dev/disk/by-label/[label]"
>>
>> Not sure how much upheaval the abolition of img_label would cause, though.
>>
> 
> Please do one logic change at time.
> Wheel, I never used loopback method other than just for test it per user
> request when it was implemented.
> Why remove img_label= it does look good for keep thing easy to
> reference, sure archisolabel= can also be removed...
> 
> 
> 

Perhaps the following change is more acceptable. Admittedly, in many situations,
using label can be quite practical.

Booting from iso, in general, comes in handy; you don't need to overwrite a whole flash.
On efi systems it is sufficient to simply copy /EFI/ and /boot/ directory from some
distro with grub, then copy the iso file to /boot/iso/, tailor /boot/grub/grub.cfg
and you have an (efi) bootable flash, without a need to overwrite the flashdrive.

diff --git a/archiso/initcpio/hooks/archiso_loop_mnt b/archiso/initcpio/hooks/archiso_loop_mnt
index 46338e5..f95a47d 100644
--- a/archiso/initcpio/hooks/archiso_loop_mnt
+++ b/archiso/initcpio/hooks/archiso_loop_mnt
@@ -18,7 +18,9 @@ archiso_loop_mount_handler () {
         echo $(readlink -f ${img_dev}) >> /run/archiso/used_block_devices
     fi
 
-    if ! _dev_loop=$(losetup --find --show --read-only "/run/archiso/img_dev/${img_loop}"); then
+    if _dev_loop=$(losetup --find --show --read-only "/run/archiso/img_dev/${img_loop}"); then
+        archisodevice="${_dev_loop}"
+    else
         echo "ERROR: Setting loopback device for file '/run/archiso/img_dev/${img_loop}'"
         launch_interactive_shell
     fi
diff --git a/docs/README.altbootmethods b/docs/README.altbootmethods
index 3c07e03..9df20ef 100644
--- a/docs/README.altbootmethods
+++ b/docs/README.altbootmethods
@@ -31,14 +31,14 @@ Note: Described method is for using with GRUB2.
 menuentry "Arch Linux (x86_64)" {
     set isofile="/<TARGET-PATH>/archlinux-<YYYY>.<MM>.<DD>-dual.iso"
     loopback loop (hd<D>,<P>)$isofile
-    linux (loop)/arch/boot/x86_64/vmlinuz archisolabel=<FS-LABEL> img_label=<TARGET-FS-LABEL> img_loop=$isofile
+    linux (loop)/arch/boot/x86_64/vmlinuz img_label=<TARGET-FS-LABEL> img_loop=$isofile
     initrd (loop)/arch/boot/x86_64/archiso.img
 }
 
 menuentry "Arch Linux (i686)" {
     set isofile="/<TARGET-PATH>/archlinux-<YYYY>.<MM>.<DD>-dual.iso"
     loopback loop (hd<D>,<P>)$isofile
-    linux (loop)/arch/boot/i686/vmlinuz archisolabel=<FS-LABEL> img_label=<TARGET-FS-LABEL> img_loop=$isofile
+    linux (loop)/arch/boot/i686/vmlinuz img_label=<TARGET-FS-LABEL> img_loop=$isofile
     initrd (loop)/arch/boot/i686/archiso.img
 }
 
diff --git a/docs/README.bootparams b/docs/README.bootparams
index 356375d..48a1c3a 100644
--- a/docs/README.bootparams
+++ b/docs/README.bootparams
@@ -20,6 +20,9 @@ INDEX
 * archisolabel=     Set the filesystem label where archiso files reside.
                     Default: (unset)
 * archisodevice=    Set the device node where archiso medium is located.
+                    Upon successful mount of the iso image specified by
+                    img_dev and img_loop, it is automatically set to the
+                    appropriate loop device.
                     Default: "/dev/disk/by-label/${archisolabel}"
 * archisobasedir=   Set the base directory where all files reside.
                     Default: "arch"
