Taking a look at the rootfs footprint of a LiveCD and a disk (image)

Archive: First Footprint on the Moon (NASA, Marshall, 07/69){width=”275” height=”248”}

Besides the details about Node’s memory footprint, it was also intersting to see how much space we gain form the rootfs by our minimization efforts.

The idea is to take a recent oVirt Node image, and compare some stats of it, to the stats of a regular image, build using the @core group.

The two points I investigated are:

  • How does the minimization affect the number of packages?
  • How does the minimization affect the space requirements?

The

  • first one was addressed by counting the number of installed packages (rpm)
  • the second one was addressed by
    • Summing up the reported size of the installed packages (rpm)
    • Determining the disk space in use (df)

Because guestfish'ing into a LiveCD is tiresome, I created this script to gather the stats for me. Additionally it’s nice to have a tool by hand to create reproducable results.

The results are - once again - interesting.

$ bash img-stats.sh ovirt-node-iso-scratch.iso runtime-layout.img
Image: ovirt-node-iso-scratch.iso
ImageSize: 197.00 MB
in_node
  NumPkgs:    449
  SizePkgs:   867.50 MB
  SizeRootfs: 564.97 MB

Image: runtime-layout.img
ImageSize: 1543.63 MB
in_imgbased
  NumPkgs:    490
  SizePkgs:   1071.67 MB
  SizeRootfs: 1323.57 MB

DiffNum: -41
DiffSizePkgs: -204.17
DiffSizeRootfs: -758.60

What do we see here?

  • We see that the plain rootfs has 41 additional packages installed. Or the other way round: 41 packages are blacklisted on the LiveCD.
  • The sum of reported rpm sizes is ~200 MB higher on the plain rootfs than on the livecd
  • The disk usage on the plain rootfs is ~760 MB higher than on the livecd

Especially the last two points indicate that the file based blacklisting is actually responsible for freeing up so much space.

This is just a rough estimate. More time needs to be spend on investigating the details of this differences.

::: {#footer} [ June 17th, 2014 1:56pm ]{#timestamp} [fedora]{.tag} [node]{.tag} [livecd]{.tag} [rootfs]{.tag} [minimization]{.tag} [libguestfs]{.tag} :::