直接取自info dd
（注意：这是从 [Lubuntu] 20.04 盒子中获取的；因此它可能包含您的版本中不存在的标志，因此您最好info dd在自己的盒子上使用以准确查看您的系统可用的内容）
\n\n\noflag=FLAG[,FLAG]...\xe2\x80\x99\n 使用 FLAG\n 参数指定的标志访问输出文件。（任何逗号周围都没有空格。）
\n\nRun Code Online (Sandbox Code Playgroud)\nHere are the flags. Not every flag is supported on every operating\n system.\n\n \xe2\x80\x98append\xe2\x80\x99\n Write in append mode, so that even if some other process is\n writing to this file, every \xe2\x80\x98dd\xe2\x80\x99 write will append to the\n current contents of the file. This flag makes sense only for\n output. If you combine this flag with the \xe2\x80\x98of=FILE\xe2\x80\x99 operand,\n you should also specify \xe2\x80\x98conv=notrunc\xe2\x80\x99 unless you want the\n output file to be truncated before being appended to.\n\n \xe2\x80\x98cio\xe2\x80\x99\n Use concurrent I/O mode for data. This mode performs direct\n I/O and drops the POSIX requirement to serialize all I/O to\n the same file. A file cannot be opened in CIO mode and with a\n standard open at the same time.\n\n \xe2\x80\x98direct\xe2\x80\x99\n Use direct I/O for data, avoiding the buffer cache. Note that\n the kernel may impose restrictions on read or write buffer\n sizes. For example, with an ext4 destination file system and\n a Linux-based kernel, using \xe2\x80\x98oflag=direct\xe2\x80\x99 will cause writes\n to fail with \xe2\x80\x98EINVAL\xe2\x80\x99 if the output buffer size is not a\n multiple of 512.\n\n \xe2\x80\x98directory\xe2\x80\x99\n\n Fail unless the file is a directory. Most operating systems\n do not allow I/O to a directory, so this flag has limited\n utility.\n\n \xe2\x80\x98dsync\xe2\x80\x99\n Use synchronized I/O for data. For the output file, this\n forces a physical write of output data on each write. For the\n input file, this flag can matter when reading from a remote\n file that has been written to synchronously by some other\n process. Metadata (e.g., last-access and last-modified time)\n is not necessarily synchronized.\n\n \xe2\x80\x98sync\xe2\x80\x99\n Use synchronized I/O for both data and metadata.\n\n \xe2\x80\x98nocache\xe2\x80\x99\n Request to discard the system data cache for a file. When\n count=0 all cached data for the file is specified, otherwise\n the cache is dropped for the processed portion of the file.\n Also when count=0, failure to discard the cache is diagnosed\n and reflected in the exit status.\n\n Note data that is not already persisted to storage will not be\n discarded from cache, so note the use of the \xe2\x80\x9csync\xe2\x80\x9d options in\n the examples below, which are used to maximize the\n effectiveness of the \xe2\x80\x98nocache\xe2\x80\x99 flag.\n\n Here are some usage examples:\n\n # Advise to drop cache for whole file\n dd if=ifile iflag=nocache count=0\n\n # Ensure drop cache for the whole file\n dd of=ofile oflag=nocache conv=notrunc,fdatasync count=0\n\n # Advise to drop cache for part of file\n # Note the kernel will only consider complete and\n # already persisted pages.\n dd if=ifile iflag=nocache skip=10 count=10 of=/dev/null\n\n # Stream data using just the read-ahead cache.\n # See also the \xe2\x80\x98direct\xe2\x80\x99 flag.\n dd if=ifile of=ofile iflag=nocache oflag=nocache,sync\n\n \xe2\x80\x98nonblock\xe2\x80\x99\n Use non-blocking I/O.\n\n \xe2\x80\x98noatime\xe2\x80\x99\n Do not update the file\xe2\x80\x99s access timestamp. *Note File\n timestamps::. Some older file systems silently ignore this\n flag, so it is a good idea to test it on your files before\n relying on it.\n\n \xe2\x80\x98noctty\xe2\x80\x99\n Do not assign the file to be a controlling terminal for \xe2\x80\x98dd\xe2\x80\x99.\n This has no effect when the file is not a terminal. On many\n hosts (e.g., GNU/Linux hosts), this option has no effect at\n all.\n\n \xe2\x80\x98nofollow\xe2\x80\x99\n Do not follow symbolic links.\n\n \xe2\x80\x98nolinks\xe2\x80\x99\n Fail if the file has multiple hard links.\n\n \xe2\x80\x98binary\xe2\x80\x99\n Use binary I/O. This option has an effect only on nonstandard\n platforms that distinguish binary from text I/O.\n\n \xe2\x80\x98text\xe2\x80\x99\n Use text I/O. Like \xe2\x80\x98binary\xe2\x80\x99, this option has no effect on\n standard platforms.\n\n \xe2\x80\x98fullblock\xe2\x80\x99\n Accumulate full blocks from input. The \xe2\x80\x98read\xe2\x80\x99 system call may\n return early if a full block is not available. When that\n happens, continue calling \xe2\x80\x98read\xe2\x80\x99 to fill the remainder of the\n block. This flag can be used only with \xe2\x80\x98iflag\xe2\x80\x99. This flag is\n useful with pipes for example as they may return short reads.\n In that case, this flag is needed to ensure that a \xe2\x80\x98count=\xe2\x80\x99\n argument is interpreted as a block count rather than a count\n of read operations.\n\n \xe2\x80\x98count_bytes\xe2\x80\x99\n Interpret the \xe2\x80\x98count=\xe2\x80\x99 operand as a byte count, rather than a\n block count, which allows specifying a length that is not a\n multiple of the I/O block size. This flag can be used only\n with \xe2\x80\x98iflag\xe2\x80\x99.\n\n \xe2\x80\x98skip_bytes\xe2\x80\x99\n Interpret the \xe2\x80\x98skip=\xe2\x80\x99 operand as a byte count, rather than a\n block count, which allows specifying an offset that is not a\n multiple of the I/O block size. This flag can be used only\n with \xe2\x80\x98iflag\xe2\x80\x99.\n\n \xe2\x80\x98seek_bytes\xe2\x80\x99\n Interpret the \xe2\x80\x98seek=\xe2\x80\x99 operand as a byte count, rather than a\n block count, which allows specifying an offset that is not a\n multiple of the I/O block size. This flag can be used only\n with \xe2\x80\x98oflag\xe2\x80\x99.\n\n These flags are not supported on all systems, and \xe2\x80\x98dd\xe2\x80\x99 rejects\n attempts to use them when they are not supported. When reading\n from standard input or writing to standard output, the \xe2\x80\x98nofollow\xe2\x80\x99\n and \xe2\x80\x98noctty\xe2\x80\x99 flags should not be specified, and the other flags\n (e.g., \xe2\x80\x98nonblock\xe2\x80\x99) can affect how other processes behave with the\n affected file descriptors, even after \xe2\x80\x98dd\xe2\x80\x99 exits.\n
man dd将提供快速的manual.reference.page信息，您可以使用许多复杂的命令info来查看其他页面。