昨天看见rsync同步后用du -sh 显示的目录大小不同,感觉很困惑,以为同步出错,结果反复查也无果,今天来公司,上QQ群里问,最后确定是磁盘的block size 大小问题,经过 tune2fs -l /dev/sda1   命令查看,发现果然block size 一个是4096 一个是1024,故而确定 du 是文件所占用的磁盘空间大小,不是文件的实际大小;
block size 不一样,或者所占用的 blocks 数量不一样都会导致这种差异
 
[root@server02 down]# du --help
用法:du [选项]... [文件]...
总结每个<文件>的磁盘用量,目录则取总用量。
长选项必须用的参数在使用短选项时也是必须的。
  -a, --all             write counts for all files, not just directories
      --apparent-size   print apparent sizes, rather than disk usage; although
                          the apparent size is usually smaller, it may be
                          larger due to holes in (`sparse') files, internal
                          fragmentation, indirect blocks, and the like
  -B, --block-size=SIZE use SIZE-byte blocks
  -b, --bytes           equivalent to `--apparent-size --block-size=1'
  -c, --total           produce a grand total
  -D, --dereference-args  dereference FILEs that are symbolic links
  -H                    like --si, but also evokes a warning; will soon
                        change to be equivalent to --dereference-args (-D)
  -h, --human-readable  print sizes in human readable format (e.g., 1K 234M 2G)
      --si              like -h, but use powers of 1000 not 1024
  -k                    like --block-size=1K
  -l, --count-links     count sizes many times if hard linked
  -L, --dereference     dereference all symbolic links
  -P, --no-dereference  don't follow any symbolic links (this is the default)
  -0, --null            end each output line with 0 byte rather than newline
  -S, --separate-dirs   do not include size of subdirectories
  -s, --summarize       display only a total for each argument
  -x, --one-file-system  skip directories on different filesystems
  -X FILE, --exclude-from=FILE  Exclude files that match any pattern in FILE.
      --exclude=PATTERN Exclude files that match PATTERN.
      --max-depth=N     print the total for a directory (or file, with --all)
                          only if it is N or fewer levels below the command
                          line argument;  --max-depth=0 is the same as
                          --summarize
      --help     显示此帮助信息并离开
      --version  显示版本信息并离开
SIZE may be (or may be an integer optionally followed by) one of following:
kB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T, P, E, Z, Y.