# sudo dnf update# sudo dnf install dnf-plugin-system-upgrade# sudo dnf upgrade --refresh# sudo dnf system-upgrade download --releasever=42# sudo dnf system-upgrade reboot（注意：系统会重启，并在后台升级系统，这个步骤可能会持续很长一段时间，根据虚拟机的硬件性能而定）
目录 & 文件位置
/proc/self/mountstats目录 & 文件性质
文件
目录 & 文件来源
Linux 安装时同时创建
目录 & 文件作用
存储系统所有挂载的文件
目录 & 文件位置
/proc/fs/nfsd/*
/proc/fs/nfs/*
/proc/net/rpc/*/content目录 & 文件性质
文件
目录 & 文件来源
启动 NFS 服务或者挂载 NFS 服务时创建
目录 & 文件作用
存储系统所有 NFS 服务启动时的文件和挂载 NFS 目录时的文件
目录 & 文件位置
/etc/rc.d/目录 & 文件性质
软连接文件，指向 init.d 目录
目录 & 文件来源
由 insserv-compat 软件包安装时自动创建
目录 & 文件作用
开机是自动执行此目录 & 文件下的文件
# zypper in insserv-compaterror: unpacking of archive failed on file /etc/rc.d: cpio: File from package already exists as a directory in system# rm -r /etc/rc.d# zypper in insserv-compat（补充：这里以在 openSUSE & SLES 上安装 insserv-compat 软件包为例）
某些服务没有开机自启例如 NetworkManager.service
在系统日志里可以类似 …… Job network.target/start deleted to break ordering cycle starting with …… 报错例如：
# cat /var/log/messages
Jan 1 10:09:24 server systemd[1]: network-online.target: Found ordering cycle on network.target/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Found dependency on NetworkManager.service/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Found dependency on basic.target/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Found dependency on slices.target/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Found dependency on mysql.slice/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Found dependency on remote-fs.target/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Found dependency on remote-fs-pre.target/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Found dependency on iscsi.service/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Found dependency on network-online.target/start
Jan 1 10:09:24 server systemd[1]: network-online.target: Job network.target/start deleted to break ordering cycle starting with network-online.target/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found ordering cycle on NetworkManager.service/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found dependency on basic.target/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found dependency on slices.target/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found dependency on mysql.slice/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found dependency on remote-fs.target/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found dependency on remote-fs-pre.target/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found dependency on iscsi.service/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found dependency on network-online.target/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Found dependency on NetworkManager-wait-online.service/start
Jan 1 10:09:24 server systemd[1]: NetworkManager-wait-online.service: Job NetworkManager.service/start deleted to break ordering cycle starting with NetworkManager-wait-online.service/start从案例中日志里的内容可以判断：
1) network.target/NetworkManager.service 启动
2) NetworkManager.service 作为基础服务依赖 basic.target
3) basic.target 依赖所有 slice 包括 mysql.slice
4) mysql.slice 依赖 iscsi.service/remote-fs.target/remote-fs-pre.target
5) iscsi.service/remote-fs.target/remote-fs-pre.target 依赖 network.target/NetworkManager.service
6) 系统为了防止启动时陷入死循环，systemd 报错 Job NetworkManager.service/start deleted to break ordering cycle 并放弃启动 NetworkManager.service
取消不太重要的服务的依赖要求
# vi /etc/systemd/system/mysql.slice将以下内容：
......
Before=slices.target
Wants=-.slice
After=-.slice remote-fs.target
......修改为：
......
Before=slices.target
Wants=-.slice
After=-.slice remote-fs.target
......（补充：这里以取消使用 /etc/systemd/system/mysql.slice 文件的服务的依赖要求为例）
[root@server ~]# hostnamectl set-hostname eternalcenter.com[root@eternalcenter ~]# hostname
eternalcenter（补充：这里只会显示 “.” 符号前面的内容，“.” 后面的内容不会在这里显示）
[root@eternalcenter ~]# hostname -f
eternalcenter.com[root@eternalcenter ~]# hostname -i[root@eternalcenter ~]# hostname -I