# 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）
$ cat test.txt
line1: Eternal Center
line2: Mingyu Zhu（
补充：这里以创建名为 test.txt 包含以下内容的文件为例
line1: Eternal Center
line2: Mingyu Zhu）
$ cat test.txt | base64 -w0
bGluZTE6IEV0ZXJuYWwgQ2VudGVyCmxpbmUyOiBNaW5neXUgWmh1Cg==（补充：这里以将 test.txt 里的内容转换为 1 行代码为例）
$ echo bGluZTE6IEV0ZXJuYWwgQ2VudGVyCmxpbmUyOiBNaW5neXUgWmh1Cg== | base64 -d
line1: Eternal Center
line2: Mingyu Zhu（补充：这里以将 1 行以下代码还原成多行内容为例
bGluZTE6IEV0ZXJuYWwgQ2VudGVyCmxpbmUyOiBNaW5neXUgWmh1Cg==）
# cat base64.sh
#!/bin/bash
myname=Eternal Ceneter
myurl=eternalcenter.com
YAML_CONTENT=$(cat << EOF
Kind: record
Metadata:
name: $myname
url: $myurl
EOF)
BASE64_YAML=$(echo "$YAML_CONTENT" | base64 -w0)
echo "echo '$BASE64_YAML'" | base64 -d | cat（注意：这个脚本最后的 cat 命令可以换成任意其他命令，让人只用输入 1 行就可以让此命令处理几行内容的输入）
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# timeout <option> <duration> <command> ......（补充：这里的 duration 是数字，默认单位是秒。也可以手动指定时间单位，时间单位可以是 s 秒、m 分钟、h 小时、d 天）
1) -k, –kill-after=DURATION 当时间到了以后强制杀死命令
2) -p, –preserve-status 当结束时保持命令本身结束时的退出代码