$ mkinitcpio  -g foo.img -k /boot/vmlinuz-linux -A autodetect,usbinput
==> Starting build: 3.7.1-1-ARCH
  -> Running build hook: [base]
  -> Running build hook: [timestamp]
  -> Running build hook: [strip]
  -> Running build hook: [shutdown]
  -> Running build hook: [autodetect]
  -> Running build hook: [usbinput]
==> Generating module dependencies
==> Creating pigz initcpio image: /home/noclaf/src/up/systemd/foo.img
==> Image generation successful

$ lsinitcpio -a foo.img
==> Image: foo.img 
==> Created with mkinitcpio 0.12.0.5.g84f9bdc
==> Kernel: 3.7.1-1-ARCH
==> Size: 2.53 MiB
==> Compressed with: gzip
  -> Uncompressed size: 6.7 MiB (.377 ratio)
  -> Estimated extraction time: 0.056s

==> Included modules:
  ahci [explicit]         ehci-hcd                hid                     jbd2                    libata                  scsi_mod                uhci-hcd                usbcore                 xhci-hcd
  crc16                   ext4 [explicit]         hid-generic             libahci                 mbcache                 sd_mod [explicit]       usb-common              usbhid

==> Included binaries:
  blkid                   cp                      fsck                    kmod                    mount                   systemd-timestamp
  busybox                 findmnt                 fsck.ext4               lsblk                   switch_root

==> Cleanup hook run order:
  shutdown