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readahead is the file prefetching technology used in the Linux operating system. It is a system call that loads a file's contents into the page cache. When a file is subsequently accessed, its contents are read from physical memory rather than from disk, which is much faster.[1]

Many distributions of Linux use readahead on a list of commonly used files to speed up booting. In such a setup, if the kernel is booted with the profile parameter, it will record all file accesses during bootup and write a new list of files to be read before booting. This will make additional installed services start faster, because they are not included in the default readahead list.[1]

For Linux distributions which are using systemd, readahead is replaced by systemd-readahead.[2][3]


  1. ^ a b "readahead(2) - Linux manual page". Retrieved 2014-04-09. 
  2. ^ "Readahead". Retrieved 2014-04-09. 
  3. ^ "systemd-readahead-replay.service". 2014-03-26. Retrieved 2014-04-09.