[root@localhost ~]# ln --help
用法：ln [选项]... [-T] 目标 链接名     (第一种格式)或：ln [选项]... 目标         (第二种格式)或：ln [选项]... 目标... 目录 (第三种格式)或：ln [选项]... -t 目录 目标...      (第四种格式)
In the 1st form, create a link to TARGET with the name LINK_NAME.
In the 2nd form, create a link to TARGET in the current directory.
In the 3rd and 4th forms, create links to each TARGET in DIRECTORY.
Create hard links by default, symbolic links with --symbolic.
By default, each destination (name of new link) should not already exist.
When creating hard links, each TARGET must exist.  Symbolic links
can hold arbitrary text; if later resolved, a relative link is
interpreted in relation to its parent directory.Mandatory arguments to long options are mandatory for short options too.--backup[=CONTROL]        为每个已存在的目标文件创建备份文件-b                            类似--backup，但不接受任何参数-d, -F, --directory           创建指向目录的硬链接(只适用于超级用户)-f, --force                   强行删除任何已存在的目标文件-i, --interactive           prompt whether to remove destinations-L, --logical               dereference TARGETs that are symbolic links-n, --no-dereference        treat LINK_NAME as a normal file ifit is a symbolic link to a directory-P, --physical              make hard links directly to symbolic links-r, --relative              create symbolic links relative to link location-s, --symbolic              make symbolic links instead of hard links-S, --suffix=SUFFIX         override the usual backup suffix-t, --target-directory=DIRECTORY  specify the DIRECTORY in which to createthe links-T, --no-target-directory   treat LINK_NAME as a normal file always-v, --verbose               print name of each linked file--help            显示此帮助信息并退出--version         显示版本信息并退出The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.
The version control method may be selected via the --backup option or through
the VERSION_CONTROL environment variable.  Here are the values:none, off       不进行备份(即使使用了--backup 选项)numbered, t     备份文件加上数字进行排序existing, nil   若有数字的备份文件已经存在则使用数字，否则使用普通方式备份simple, never   永远使用普通方式备份Using -s ignores -L and -P.  Otherwise, the last option specified controls
behavior when a TARGET is a symbolic link, defaulting to -P.GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
请向<http://translationproject.org/team/zh_CN.html> 报告ln 的翻译错误
要获取完整文档，请运行：info coreutils 'ln invocation'
[root@localhost ~]#

[root@localhost ~]# chkconfig --list denyhosts注意：该输出结果只显示 SysV 服务，并不包含原生 systemd 服务。SysV 配置数据可能被原生 systemd 配置覆盖。如果您想列出 systemd 服务,请执行 'systemctl list-unit-files'。欲查看对特定 target 启用的服务请执行'systemctl list-dependencies [target]'。denyhosts       0:关    1:关    2:开    3:开    4:开    5:开    6:关