Building an Arch Linux based live CD/USB

Question

After bootstrapping my Arch live CD, I try to install the archiso package with:

pacman -Sy archiso

but I get:

error: failed to commit transaction (conflicting files)
archiso: /usr/lib/initcpio/archiso_shutdown exists in filesystem
archiso: /usr/lib/initcpio/hooks/archiso exists in filesystem
archiso: /usr/lib/initcpio/hooks/archiso_loop_mnt exists in filesystem
archiso: /usr/lib/initcpio/hooks/archiso_pxe_common exists in filesystem
archiso: /usr/lib/initcpio/hooks/archiso_pxe_http exists in filesystem
archiso: /usr/lib/initcpio/hooks/archiso_pxe_nbd exists in filesystem
archiso: /usr/lib/initcpio/hooks/archiso_pxe_nfs exists in filesystem
archiso: /usr/lib/initcpio/hooks/archiso_shutdown exists in filesystem
archiso: /usr/lib/initcpio/install/archiso exists in filesystem
archiso: /usr/lib/initcpio/install/archiso_kms exists in filesystem
archiso: /usr/lib/initcpio/install/archiso_loop_mnt exists in filesystem
archiso: /usr/lib/initcpio/install/archiso_pxe_common exists in filesystem
archiso: /usr/lib/initcpio/install/archiso_pxe_http exists in filesystem
archiso: /usr/lib/initcpio/install/archiso_pxe_nbd exists in filesystem
archiso: /usr/lib/initcpio/install/archiso_pxe_nfs exists in filesystem
archiso: /usr/lib/initcpio/install/archiso_shutdown exists in filesystem
Errors occurred, no packages were upgraded.

I read pacman wiki. So I tried:

pacman -Qo  /usr/lib/initcpio/archiso_shutdown 

and I get:

error: No package owns /usr/lib/initcpio/archiso_shutdown

As for:

If you had installed a program manually without using pacman or a frontend, you have to remove it and all its files and reinstall properly using pacman.

After bootstrapping the live CD, pacman is the first program run.

Answer 1

Never synch the database without updating your packages. Always use pacman -Syu, otherwise you may experience the sort of breakage you are seeing.

Essentially, you have told pacman to refresh it's local database listing for a specific package, and not updated any of the other packages (that may share libraries) at the same time. This is why partial upgrades are unsupported.

You can read the parable of the sad user that fell into this trap for a more concrete example.