The spacewalk client install needs some workarounds as the arm packages are not available. The advantage is that all but one package are available as architecture independant packages. The workaround is to use the x86_64 client repository and compile the remaining package.
cat >> /etc/yum.repos.d/spacewalk-2.8-client.repo << EOF
[group_spacewalkproject-spacewalk-2.8-client]
name=Copr repo for spacewalk-2.8-client owned by @spacewalkproject
baseurl=https://copr-be.cloud.fedoraproject.org/results/@spacewalkproject/spacewalk-2.8-client/epel-7-$basearch/
type=rpm-md
skip_if_unavailable=True
gpgcheck=1
gpgkey=https://copr-be.cloud.fedoraproject.org/results/@spacewalkproject/spacewalk-2.8-client/pubkey.gpg
repo_gpgcheck=0
enabled=1
enabled_metadata=1
EOF
yum install -y rhn-client-tools http://<spacewalk server>/pub/rhn-org-trusted-ssl-cert-1.0-2.noarch.rpm rhncfg-actions rhncfg rhncfg-client m2crypto
cd /tmp
yum install -y gettext rpm-build yum-utils gcc make
yumdownloader --source rhnsd
rpmbuild --rebuild rhnsd* # you are not supposed to build this as root... but it works...
yum install -y ~/rpmbuild/RPMS/armv7hl/rhnsd-5*
rhn-actions-control --enable-all # after provisioning install
rhnreg_ks --serverUrl=https://<spacewalk server>/XMLRPC --activationkey=1-centos7-armhfp --sslCACert=/usr/share/rhn/RHN-ORG-TRUSTED-SSL-CERT