Accelerating the diskless initrd and rootimg generating

Generating diskless initrd with genimage and compressed rootimg with packimage and liteimg is a time-comsuming process, it can be accelerated by enabling paralell compression tool pigz on the management node with multiple processors and cores. See Appendix for an example on packimage performance optimized with pigz enabled.

Enabling the pigz for diskless initrd and rootimg generating

The paralell compression tool pigz can be enabled by installing pigz package on the management server or diskless rootimg. Depending on the method of generating the initrd and compressed rootimg, the steps differ in different Linux distributions.

  • [RHEL]

    The package pigz is shipped in Extra Packages for Enterprise Linux (or EPEL) instead of RedHat iso, this involves some complexity.

    Extra Packages for Enterprise Linux (or EPEL) is a Fedora Special Interest Group that creates, maintains, and manages a high quality set of additional packages for Enterprise Linux, including, but not limited to, Red Hat Enterprise Linux (RHEL), CentOS and Scientific Linux (SL), Oracle Linux (OL).

    EPEL has an epel-release package that includes gpg keys for package signing and repository information. Installing this package for your Enterprise Linux version should allow you to use normal tools such as yum to install packages and their dependencies.

    Refer to the http://fedoraproject.org/wiki/EPEL for more details on EPEL

    1. Enabling the pigz in genimage (only supported in RHELS6 or above)

      pigz should be installed in the diskless rootimg. Download pigz package from https://dl.fedoraproject.org/pub/epel/ , then customize the diskless osimage to install pigz as the additional packages, see Install Additional Other Packages for more details.

    2. Enabeling the pigz in packimage

      pigz should be installed on the management server. Download pigz package from https://dl.fedoraproject.org/pub/epel/ , then install the pigz with yum or rpm.

  • [UBUNTU]

    Make sure the pigz is installed on the management node with the following command:

    dpkg -l|grep pigz

    If not, pigz can be installed with the following command:

    apt-get install pigz

  • [SLES]

    1. Enabling the pigz in genimage (only supported in SLES12 or above)

      pigz should be installed in the diskless rootimg, since``pigz`` is shipped in the SLES iso, this can be done by adding pigz into the pkglist of diskless osimage.

    2. Enabling the pigz in packimage

      Make sure the pigz is installed on the management node with the following command:

      rpm -qa|grep pigz

      If not, pigz can be installed with the following command:

      zypper install pigz

Appendix: An example on packimage performance optimization with “pigz” enabled

This is an example on performance optimization with pigz enabled.

In this example, a xCAT command packimage rhels7-ppc64-netboot-compute is run on a Power 7 machine with 4 cores.

The system info:

# uname -a
Linux c910f03c01p03 3.10.0-123.el7.ppc64 #1 SMP Mon May 5 11:18:37 EDT 2014 ppc64 ppc64 ppc64 GNU/Linux

# cat /etc/os-release
NAME="Red Hat Enterprise Linux Server"
VERSION="7.0 (Maipo)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="7.0"
PRETTY_NAME="Red Hat Enterprise Linux Server 7.0 (Maipo)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:7.0:GA:server"
HOME_URL="https://www.redhat.com/"
BUG_REPORT_URL="https://bugzilla.redhat.com/"

REDHAT_BUGZILLA_PRODUCT="Red Hat Enterprise Linux 7"
REDHAT_BUGZILLA_PRODUCT_VERSION=7.0
REDHAT_SUPPORT_PRODUCT="Red Hat Enterprise Linux"
REDHAT_SUPPORT_PRODUCT_VERSION=7.0

The CPU info:

# cat /proc/cpuinfo
processor       : 0
cpu             : POWER7 (architected), altivec supported
clock           : 3550.000000MHz
revision        : 2.0 (pvr 003f 0200)

processor       : 1
cpu             : POWER7 (architected), altivec supported
clock           : 3550.000000MHz
revision        : 2.0 (pvr 003f 0200)

processor       : 2
cpu             : POWER7 (architected), altivec supported
clock           : 3550.000000MHz
revision        : 2.0 (pvr 003f 0200)

processor       : 3
cpu             : POWER7 (architected), altivec supported
clock           : 3550.000000MHz
revision        : 2.0 (pvr 003f 0200)

timebase        : 512000000
platform        : pSeries
model           : IBM,8233-E8B
machine         : CHRP IBM,8233-E8B

The time spent on packimage with gzip:

# time packimage rhels7-ppc64-netboot-compute
Packing contents of /install/netboot/rhels7/ppc64/compute/rootimg
compress method:gzip


real    1m14.896s
user    0m0.159s
sys     0m0.019s

The time spent on packimage with pigz:

# time packimage rhels7-ppc64-netboot-compute
Packing contents of /install/netboot/rhels7/ppc64/compute/rootimg
compress method:pigz

real    0m23.177s
user    0m0.176s
sys     0m0.016s