* initramfs-tools in impish has changed default initrd compression to zstd. To allow compressing and uncompressing such initrds on Focal LTS release we should backport zstd support in the mkinitramfs & unmkinitramffs tooling. For example ubuntu-cdimage uses unmkinitramfs tool to unpack and inspect impish initrds on a focal host.
* Uncompress it with $ unmkinitramfs ./zstd-initrd.img zstd-initrd-unpacked
[Where problems could occur]
* This adds support for zstd compressed initrd in both mkinitramfs and unmkinitramfs. However our GA kernels do not support zstd compressed initrds. And depends on zstd package is not added either. Meaning one still has to install zstd to gain the unpack support. Changing initramfs.conf to zstd may result in unbootable instance when used with GA kernel.
[Impact]
* initramfs-tools in impish has changed default initrd compression to zstd. To allow compressing and uncompressing such initrds on Focal LTS release we should backport zstd support in the mkinitramfs & unmkinitramffs tooling. For example ubuntu-cdimage uses unmkinitramfs tool to unpack and inspect impish initrds on a focal host.
[Test Plan]
* Create initrd with zstd $ mkinitramfs -c zstd -o zstd-initrd.img
* Uncompress it with $ unmkinitramfs ./zstd-initrd.img zstd-initrd- unpacked
[Where problems could occur]
* This adds support for zstd compressed initrd in both mkinitramfs and unmkinitramfs. However our GA kernels do not support zstd compressed initrds. And depends on zstd package is not added either. Meaning one still has to install zstd to gain the unpack support. Changing initramfs.conf to zstd may result in unbootable instance when used with GA kernel.