yum install -y passwd openssl openssh-server openssh-clients net-tools nc net-tools vim wget
wget https://copr.fedorainfracloud.org/coprs/jsynacek/systemd-backports-for-centos-7/repo/epel-7/jsynacek-systemd-backports-for-centos-7-epel-7.repo -O /etc/yum.repos.d/jsynacek-systemd-centos-7.repo
更新内核版本：
yum update systemd