dd命令的用法
发布时间:2020-12-15 09:22:56 所属栏目:安全 来源:网络整理
导读:脚本会根据剩余空间的大小来计算一个参数,剩余空间很多时,参数值为A;剩余空间较少时,参数值为剩余空间大小的函数;剩余空间有1G时,总是值A;为了验证参数值为剩余空间大小的函数的情况,需要使获得的剩余空间的值小一些,此时,我们可以使用dd命令来创
命令使用示例: [root@db22 ~]# df -m /home
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda3 18043 13072 4055 77% /
[root@db22 ~]# dd if=/dev/zero of=/tmp/holdspace.fil bs=1M count=3000
3000+0 records in
3000+0 records out
3145728000 bytes (3.1 GB) copied,8.92085 s,353 MB/s
[root@db22 ~]# df -m /home
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/sda3 18043 16072 1055 94% /
上面的示例命令可以看到可用空间从4055M变成了1055M,是因为我们创建了一个3000M的空白文件holdspace.fil。 通过man来看一下dd命令的用法NAME
dd - convert and copy a file
SYNOPSIS
dd [OPERAND]...
dd OPTION
DESCRIPTION
Copy a file,converting and formatting according to the operands.
bs=BYTES
read and write BYTES bytes at a time (also see ibs=,obs=)
每一次读写BYTES个字节
cbs=BYTES
convert BYTES bytes at a time
每一次转换BYTES个字节
conv=CONVS
convert the file as per the comma separated symbol list
count=BLOCKS
copy only BLOCKS input blocks
只拷贝BLOCKS个输入块。
ibs=BYTES
read BYTES bytes at a time (default: 512)
if=FILE
read from FILE instead of stdin
iflag=FLAGS
read as per the comma separated symbol list
obs=BYTES
write BYTES bytes at a time (default: 512)
of=FILE
write to FILE instead of stdout
oflag=FLAGS
write as per the comma separated symbol list
seek=BLOCKS
skip BLOCKS obs-sized blocks at start of output
skip=BLOCKS
skip BLOCKS ibs-sized blocks at start of input
status=noxfer
suppress transfer statistics
BLOCKS and BYTES may be followed by the following multiplicative suffixes: c =1,w =2,b =512,kB =1000,K =1024,MB
=1000*1000,M =1024*1024,xM =M GB =1000*1000*1000,G =1024*1024*1024,and so on for T,P,E,Z,Y.
Each CONV symbol may be:
ascii from EBCDIC to ASCII
ebcdic from ASCII to EBCDIC
... ...
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