From Gentoo Wiki
Jump to:navigation Jump to:search
This article is a stub. Please help out by expanding it - how to get started.

zstd is a fast, lossless compression algorithm and tool suite. zstd is available in the Linux kernel to support initramfs compression, compressed kernel modules, and compressed swap space.

zstd originated at Facebook.



General setup  --->
   Kernel compression mode (ZSTD)  --->
      (X) ZSTD
   [*] Initial RAM filesystem and RAM disk (initramfs/initrd) support
      [*]   Support initial ramdisk/ramfs compressed using ZSTD
[*] Enable loadable module support  --->
   Module compression mode (ZSTD)  --->
      (X) ZSTD
Memory Management options  --->
   [*] Compressed cache for swap pages (EXPERIMENTAL)
      Compressed cache for swap pages default compressor (zstd)  --->
         (X) zstd
Cryptographic API  --->
   {*}   Zstd compression algorithm
File systems  --->
   <M> F2FS filesystem support
      [*]     ZSTD compression support

USE flags

USE flags for app-arch/zstd zstd fast compression library

lz4 Enable support for lz4 compression (as implemented in app-arch/lz4)
split-usr Enable behavior to support maintaining /bin, /lib*, /sbin and /usr/sbin separately from /usr/bin and /usr/lib*
static-libs Build static versions of dynamic libraries as well


root #emerge --ask app-arch/zstd



user $zstd --help
*** zstd command line interface 64-bits v1.5.2, by Yann Collet ***
Usage : 
      zstd [args] [FILE(s)] [-o file] 

FILE    : a filename 
          with no FILE, or when FILE is - , read standard input
Arguments : 
 -#     : # compression level (1-19, default: 3) 
 -d     : decompression 
 -D DICT: use DICT as Dictionary for compression or decompression 
 -o file: result stored into `file` (only 1 output file) 
 -f     : disable input and output checks. Allows overwriting existing files,
          input from console, output to stdout, operating on links,
          block devices, etc.
--rm    : remove source file(s) after successful de/compression 
 -k     : preserve source file(s) (default) 
 -h/-H  : display help/long help and exit 

Advanced arguments : 
 -V     : display Version number and exit 
 -c     : write to standard output (even if it is the console) 
 -v     : verbose mode; specify multiple times to increase verbosity 
 -q     : suppress warnings; specify twice to suppress errors too 
--[no-]progress : forcibly display, or never display the progress counter.
                  note: any (de)compressed output to terminal will mix with progress counter text. 
 -r     : operate recursively on directories 
--filelist FILE : read list of files to operate upon from FILE 
--output-dir-flat DIR : processed files are stored into DIR 
--output-dir-mirror DIR : processed files are stored into DIR respecting original directory structure 
--[no-]check : during compression, add XXH64 integrity checksum to frame (default: enabled). If specified with -d, decompressor will ignore/validate checksums in compressed frame (default: validate).
--trace FILE : log tracing information to FILE.
--      : All arguments after "--" are treated as files 

Advanced compression arguments : 
--ultra : enable levels beyond 19, up to 22 (requires more memory) 
--long[=#]: enable long distance matching with given window log (default: 27) 
--fast[=#]: switch to very fast compression levels (default: 1) 
--adapt : dynamically adapt compression level to I/O conditions 
--[no-]row-match-finder : force enable/disable usage of fast row-based matchfinder for greedy, lazy, and lazy2 strategies 
--patch-from=FILE : specify the file to be used as a reference point for zstd's diff engine. 
 -T#    : spawns # compression threads (default: 1, 0==# cores) 
 -B#    : select size of each job (default: 0==automatic) 
--single-thread : use a single thread for both I/O and compression (result slightly different than -T1) 
--auto-threads={physical,logical} (default: physical} : use either physical cores or logical cores as default when specifying -T0 
--rsyncable : compress using a rsync-friendly method (-B sets block size) 
--exclude-compressed: only compress files that are not already compressed 
--stream-size=# : specify size of streaming input from `stdin` 
--size-hint=# optimize compression parameters for streaming input of approximately this size 
--target-compressed-block-size=# : generate compressed block of approximately targeted size 
--no-dictID : don't write dictID into header (dictionary compression only) 
--[no-]compress-literals : force (un)compressed literals 
--format=zstd : compress files to the .zst format (default) 
--format=gzip : compress files to the .gz format 
--format=xz : compress files to the .xz format 
--format=lzma : compress files to the .lzma format 
--format=lz4 : compress files to the .lz4 format 

Advanced decompression arguments : 
 -l     : print information about zstd compressed files 
--test  : test compressed file integrity 
 -M#    : Set a memory usage limit for decompression 
--[no-]sparse : sparse mode (default: enabled on file, disabled on stdout) 

Dictionary builder : 
--train ## : create a dictionary from a training set of files 
--train-cover[=k=#,d=#,steps=#,split=#,shrink[=#]] : use the cover algorithm with optional args 
--train-fastcover[=k=#,d=#,f=#,steps=#,split=#,accel=#,shrink[=#]] : use the fast cover algorithm with optional args 
--train-legacy[=s=#] : use the legacy algorithm with selectivity (default: 9) 
 -o DICT : DICT is dictionary name (default: dictionary) 
--maxdict=# : limit dictionary to specified size (default: 112640) 
--dictID=# : force dictionary ID to specified value (default: random) 

Benchmark arguments : 
 -b#    : benchmark file(s), using # compression level (default: 3) 
 -e#    : test all compression levels successively from -b# to -e# (default: 1) 
 -i#    : minimum evaluation time in seconds (default: 3s) 
 -B#    : cut file into independent blocks of size # (default: no block) 
 -S     : output one benchmark result per input file (default: consolidated result) 
--priority=rt : set process priority to real-time


zstd supports parallel compression in the main zstd utility which can be configured by environment variables or the -T parameter. It does not support parallel decompression in the main tool.

However, a contrib tool pzstd (which is installed alongside zstd) can both compress and decompress in parallel. It takes a different argument for the number of threads (-p). pzstd is not as widely used as zstd.


zstd can be configured partly environment variables: ZSTD_NBTHREADS sets the number of threads to use for compression (0 means "autodetect number available") and ZSTD_CLEVEL sets the default compression level.

Create the following file:

FILE /etc/env.d/99zstd
# Use number of threads available for parallel compression

Then run:

root #env-update && . /etc/profile


To use zstd for Portage compression of both installed files and binary packages:

FILE /etc/portage/make.conf



The kernel must be compiled with support for zstd compression!

To use Zstd for Dracut's compression of initramfs:

FILE /etc/dracut.conf.d/compression.conf


systemd has a Meson configuration option default-compression to allow choosing the preferred default compression algorithm.

To use zstd:

FILE /etc/portage/env/sys-apps/systemd

Ensure that USE=zstd is enabled on sys-apps/systemd.



root #emerge --ask --depclean --verbose app-arch/zstd

See also

  • Gzip — a data compression utility maintained by the GNU project that uses Lempel-Ziv (LZ77) encoding
  • Bzip2 — high-quality, patent free file compressor using the Burrows-Wheeler algorithm.
  • Xz-utils — LZMA2-based data compression utility.

External resources