Unit filewalld.service could not be found.

如果提示“Unit firewalld.service could not be found.”，说明防火墙服务没有安装或者没有启动。在CentOS 7下，默认的防火墙是Firewall，需要使用命令“yum install firewalld firewall-config”来安装防火墙服务。安装完成后，使用命令“systemctl start firewalld.service”来启动防火墙服务。如果防火墙服务已经安装并且启动，但是仍然提示“Unit firewalld.service could not be found.”，则可能是防火墙服务的配置文件被删除或者损坏，需要重新安装防火墙服务。

相关问题

Unit sshd..service could not be found. Unit service.service could not be found.

It seems like there is a typo in the command you are running. Instead of typing `sshd..service` or `service.service`, try typing `sshd.service` or the name of the specific service you are trying to use.

For example, to start the sshd service, you can use the following command:

sudo systemctl start sshd

To start a different service, replace `sshd` with the name of the service you want to start.

unit network.service could not be found

unit network.service could not be found 是由于系统中没有名为network.service的单元文件导致的错误。根据你提供的引用内容，你使用的是CentOS 7镜像，而CentOS 7的网络配置文件目录是/etc/sysconfig/network-scripts。在该目录下，你可以查找到名为ifcfg-ensXX（XX为数字）的配置文件，该文件对应着网络接口。你可以检查该文件中是否存在NETWORKING=yes的配置，以确保网络服务已正确配置。另外，你还可以通过执行systemctl status network.service命令来检查network.service是否已安装和启动。