rootfs: Add rootfs based on CentOS 7

Signed-off-by: Jose Carlos Venegas Munoz <jose.carlos.venegas.munoz@intel.com>

rootfs-builder/centos/Dockerfile

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+FROM centos:7

rootfs-builder/centos/RPM-GPG-KEY-CentOS-7

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+=OGYX
+-----END PGP PUBLIC KEY BLOCK-----

rootfs-builder/centos/config.sh

@@ -0,0 +1,15 @@
+# This is a configuration file add extra variables to
+# be used by build_rootfs() from rootfs_lib.sh the variables will be
+# loaded just before call the function.
+
+# Here there are a couple of variables you may need.
+# Remove them or add more 
+
+# Centos Version
+OS_VERSION=${OS_VERSION:-7}
+
+#Mandatory Packages that must be installed
+# systemd: An init system that will start kata-agent
+# iptables: Need by Kata agent
+# udevlib.so: Need by Kata agent
+PACKAGES="systemd iptables"

rootfs-builder/centos/rootfs_lib.sh

@@ -0,0 +1,134 @@
+#!/bin/bash
+#
+# Copyright (c) 2017 Intel Corporation
+#
+# SPDX-License-Identifier: Apache-2.0
+
+check_program(){
+	type "$1" >/dev/null 2>&1
+}
+
+check_root()
+{
+	if [ "$(id -u)" != "0" ]; then
+		echo "Root is needed"
+		exit 1
+	fi
+}
+
+generate_dnf_config()
+{
+	cat > "${DNF_CONF}" << EOF
+[main]
+cachedir=/var/cache/centos-osbuilder
+keepcache=0
+debuglevel=2
+logfile=/var/log/yum-centos.log
+exactarch=1
+obsoletes=1
+gpgcheck=0
+plugins=0
+installonly_limit=3
+#Dont use the default dnf reposdir
+#this will prevent to use host repositories
+reposdir=/root/mash
+
+[base]
+name=CentOS-7 - Base
+mirrorlist=http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&container=container
+#baseurl=${REPO_URL}/os/x86_64/
+gpgcheck=1
+gpgkey=file://${CONFIG_DIR}/RPM-GPG-KEY-CentOS-7
+
+#released updates 
+[updates]
+name=CentOS-7 - Updates
+mirrorlist=http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=updates&container=container
+#baseurl=${REPO_URL}/updates/x86_64/
+gpgcheck=1
+gpgkey=file://${CONFIG_DIR}/RPM-GPG-KEY-CentOS-7
+
+#additional packages that may be useful
+[extras]
+name=CentOS-7 - Extras
+mirrorlist=http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=extras&container=container
+#baseurl=${REPO_URL}/extras/x86_64/
+gpgcheck=1
+gpgkey=file://${CONFIG_DIR}/RPM-GPG-KEY-CentOS-7
+
+#additional packages that extend functionality of existing packages
+[centosplus]
+name=CentOS-7 - Plus
+mirrorlist=http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=centosplus&container=container
+#baseurl=${REPO_URL}/centosplus/x86_64/
+gpgcheck=1
+enabled=0
+gpgkey=file://${CONFIG_DIR}/RPM-GPG-KEY-CentOS-7
+EOF
+}
+
+# - Arguments
+# rootfs_dir=$1
+#
+# - Optional environment variables
+#
+# EXTRA_PKGS: Variable to add extra PKGS provided by the user
+#
+# BIN_AGENT: Name of the Kata-Agent binary
+#
+# REPO_URL: URL to distribution repository ( should be configured in 
+#           config.sh file)
+#
+# Any other configuration variable for a specific distro must be added 
+# and documented on its own config.sh
+# 
+# - Expected result
+#
+# rootfs_dir populated with rootfs pkgs
+# It must provide a binary in /sbin/init
+build_rootfs() {
+	# Mandatory
+	local ROOTFS_DIR=$1
+
+	#Name of the Kata-Agent binary
+	local BIN_AGENT=${BIN_AGENT}
+
+	# In case of support EXTRA packages, use it to allow
+	# users add more packages to the base rootfs
+	local EXTRA_PKGS=${EXTRA_PKGS:-}
+
+	#In case rootfs is created usign repositories allow user to modify
+	# the default URL
+	local REPO_URL=${REPO_URL:-http://mirror.centos.org/centos/7}
+
+	#PATH where files this script is placed
+	#Use it to refer to files in the same directory
+	#Exmaple: ${CONFIG_DIR}/foo
+	local CONFIG_DIR=${CONFIG_DIR}
+
+
+	# Populate ROOTFS_DIR
+	# Must provide /sbin/init and /bin/${BIN_AGENT}
+	check_root
+	if [ ! -f "${DNF_CONF}" ]; then
+		DNF_CONF="./kata-centos-dnf.conf"
+		generate_dnf_config
+	fi
+	mkdir -p "${ROOTFS_DIR}"
+	if [ -n "${PKG_MANAGER}" ]; then
+		info "DNF path provided by user: ${PKG_MANAGER}"
+	elif check_program "dnf"; then
+		PKG_MANAGER="dnf"
+	elif check_program "yum" ; then
+		PKG_MANAGER="yum"
+	else
+		die "neither yum nor dnf is installed"
+	fi
+
+	info "Using : ${PKG_MANAGER} to pull packages from ${REPO_URL}"
+
+	DNF="${PKG_MANAGER} --config=$DNF_CONF -y --installroot=${ROOTFS_DIR} --noplugins"
+	$DNF install ${EXTRA_PKGS} ${PACKAGES}
+
+	[ -n "${ROOTFS_DIR}" ]  && rm -r "${ROOTFS_DIR}/var/cache/centos-osbuilder"
+}