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Written by Oleksandr Gavenko (AKA gavenkoa), compiled on 2024-04-01 from rev 052223c22317.



Official mirror list.

Download installed, run it and additionally select:

Add Cygwin's /bin to Windows' PATH so you could lauch mintty and clone apt-cyg and add it to PATH too:

cd ~/work/cygwin
git clone https://github.com/kou1okada/apt-cyg
cp apt-cyg/apt-cyg ~/.local/bin

Integrate bash-completion for apt-cyg:

apt-cyg install bash-completion
apt-cyg completion-install

Important packages:


Run setup.exe. Today you should prefer 64-bit flavor because it sould less BLODA. Add Cygwin /bin directory to your PATH env var:

set PATH=c:\opt\cygwin\bin;%PATH%

Cygwin behavior can be altered via CYGWIN env var:

set CYGWIN=noglob wincmdln
The CYGWIN environment variable. Available options.

The easiest way to install env var CYGWIN is via .reg file:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment]
"CYGWIN"="noglob wincmdln"
How can I change my Cygwin home folder after installation?

Set TMP and TEMP env vars without dangerous symbols in path (without spaces, etc):

set TMP=c:\tmp
set TEMP=c:\tmp

Also you need to edit /etc/passwd to point to correct home path.

For Cygwin 1.7 /etc/nsswitch.conf settings is used to define user home. By default it is /home/%U so it is better to create symlink:

$ ln -s /cygdrive/d/home /home/user

Alternatively with native Windows symlink (from build-in cmd command):

cmd# mklink /D c:\opt\cygwin\home\user c:\home

List of installed packages (-c - check, -d - dump only):

$ cygcheck -c -d

Alternatively look to file content:


In a past I work with particular code point:

set LANG=ru_RU.cp1251

Altering LANG for anything other then C cause only problems, when you get help and error messages in non-English. It is mostlry impossible to search for keywords, when text are translated.

Mount points

In Cygwin the 3rd parameter (FS type) has special meaning:


none    /cygdrive none binary,posix=0,user,noacl 0 0
c:/opt/   /opt    none binary,noacl,user,posix=0 0 0
d:/backup /backup none binary,noacl,user,posix=0 0 0
/var     /usr/var none bind
The Cygwin Mount Table. Description of supported keys.

Recent version of Win 10 exposes WSL distros via P9 network protocol. As Cygwin supports UNC paths it is possible to add mount points (don't forget to create directory /wsl before mounting!):

//wsl$/debian /wsl/debian  ntfs binary,noacl,posix=0 0 0
//wsl$/ubuntu /wsl/ubuntu  ntfs binary,noacl,posix=0 0 0
//wsl$/alpine /wsl/alpine  ntfs binary,noacl,posix=0 0 0


Cygwin allow complex mapping Windows accounts to POSIX:

POSIX accounts, permission, and security.

Modern Cygwin (v3.x) relies on /etc/nsswitch.conf for user settings. That means there are no /etc/passwd & /etc/group and user home directory and login shell are defined according to nsswitch.conf:

db_home:  /home/%U
db_shell: /bin/bash

Earlier Cygwin used /etc/passwd & /etc/group and sometimes you were required to regenerate them:

$ mkpasswd -d | grep $yourlogin > /etc/passwd
$ mkpasswd -l > /etc/passwd
$ mkgroup -l > /etc/group


Cygwin C API man pages and user guide manuals available in cygwin-doc package.

Documentation is unpacked into /usr/share/doc/cygwin-... directories.

For system man pages install: man-pages-posix.

apt-cyg package manager

apt-cyg is based on bash, wget, tar, gawk and bzip2 packages and provide convenient commands for managing and queries packages:

$ apt-cyg update
$ apt-cyg install emacs-w32
$ apt-cyg remove emacs-w32

Information about package and dependencies:

$ apt-cyg show emacs-w32
$ apt-cyg depends wget
$ apt-cyg rdepends emacs

List installed packages:

$ apt-cyg list

Search for package with file across installed packages:

$ apt-cyg search stdio.h

List package files for installed packages:

$ apt-cyg listfiles util-linux

Search for package with file through cygwin.com:

$ apt-cyg searchall stdio.h

List all packages in setup.ini:

$ apt-cyg listall

Find package by regex:

$ apt-cyg listall ^emacs

To switch between mirrors:

$ apt-cyg mirror ftp://ftp.cygwinports.org/pub/cygwinports
$ apt-cyg update
$ apt-cyg install php

$ apt-cyg mirror ftp://www.fruitbat.org/pub/cygwin/circa/2016/08/30/104223

$ apt-cyg mirror http://mirrors.kernel.org/sources.redhat.com/cygwin/

Just switching mirror does not update metadata.

To change a location of directory where packages and setup.ini downloaded:

$ apt-cyg cache

$ apt-cyg cache ~/net
Cache set to C:\home\net.
Still maintained project with extra features.
Home page of abandoned project.
Request to support multiply sources.
How to add a repository using apt-cyg.
Depricated way to install from several sources with -m option using shell aliases as a trick.

Cygwin bash completion

Cygwin bash has extra patch that adds completion_strip_exe option:

shopt -s completion_strip_exe

If you complete executable .exe suffix is stripped if any. That halps with bash-completion because usually comletion defined for base name without .exe suffix, like:

complete -F _figlet figlet
7b. completion_strip_exe - using 'shopt -s completion_strip_exe' makes completion strip .exe suffixes.

Cygwin file permission

Get list of permissions:

$ getfacl .

rsync without problems:

$ rsync -ar —chmod=ugo=rwX $FROM/ $TO/
File permissions.
POSIX accounts, permission, and security.
Cygwin sets file permission to 000.

Installation on Windows XP

Cygwin from v2.5.5 and Setup version 2.874 (on 25 Aug 2016) is latest version with Windows XP support. Later versions build with dependencies on newer syscalls and failt to run in Windows XP.

Latest mirrors avaialble at fruitbat.org:

To run setup against this mirror:

cmd> setup.exe

setup.exe available at:

Run as (-X disable signature verification, -s <url> option select a particular mirror, -O option disallow any other mirrors):

cmd> setup-x86.exe -X -s ftp://www.fruitbat.org/pub/cygwin/circa/2016/08/30/104223 -O
Description of Cygwin time machine project.
Question about Cygwin old mirror.
Question about Cygwin old mirror.
Another old mirror.

Cygwin ports

This project provides Cygwin binary and source packages for a large variety of programs and libraries, including the GNOME and KDE desktop environments

Newest home of the Cygwin Ports project.
Home page.
Official blog.
cygport scripts to compile cygwinports
Source packaging tool for Cygwin
Cygport Reference Manual.

Which Cygwin version you run?

$ uname -r
$ cygcheck -c cygwin
Cygwin Package Information
Package              Version        Status
cygwin               1.7.7-1        OK

Rebase dll / rebaseall

Today rebaseall script takes care of DLL acrees clashes. It is shell script that should be run from ash (a special Cygwin shell that compatible with rebase process in egg-chicken mean), like you close every Cygwin program (including Windows services) and run from cmd.exe or PowerShell:

sh -c rebaseall

With modern Emacs 28.1-2 introduced native compilation for every user using Emacs you need to add Emacs's dynamic modules to the update list under /var/lib/rebase/userpath.d (user below is a placeholder):

$ cat /var/lib/rebase/userpath.d/user
Announce about handling rebase with Emacs native compilation.

In order to Cygwin to maintain fork() syscall it should preserve same logical base address for dll to be able to share library between child and parent process. It was done via special hints in dlls.

With new version of Cygwin software or external Windows libraries (AntiVirus may inject its their libraries into Cygwin process address space) it may happen that new library is overlapped with existing.

There is rebase utility that changes base address hints for dll.

You should finish all Cygwin processes in order to rebase to succeed.

You may trigger automatic rebase of all packages in next run of setup.exe with:

$ rebase-trigger full

Read more at:

How do I fix fork() failures?
Handling repeated failures of rebaseall to allow cygwin remaps.

Running X Window.

$ XWin -multiwindow&


$ XWin -clipboard -silent-dup-error -xkblayout "us,ru" -xkboptions "grp:caps_toggle"&

To start X application you must set 'DISPLAY':

$ DISPLAY=:0 xterm&

Working with packages.

List of package files.

$ cygcheck -l pkg-name

Search packages by containing path (only under installed packages).

$ for f in /etc/setup/*.lst.gz; do gzip -c -d $f | grep $WORD  2>&1 >/dev/null && { echo $f; break; } || :; done

Search for package.

If you have file name or regex use (need internet connection):

$ cygcheck -p REGEX

cygcheck use such link:


Cygwin installation info.

$ uname -a
$ cygcheck -s -r

Cygwin acronyms.

One encounters all sorts of acronyms on the Cygwin mailing lists.

Check dll dependency.

$ ldd my.dll
$ ldd my.exe
$ cygcheck ./my.dll
$ cygcheck ./my.exe

Cygwin alternatives.

Subsystem for Unix-based Applications and Services for Unix