How to update Cygwin from Cygwin's command line?

Take a look here:

• http://cygwin.com/faq.html#faq.setup

Aside from the other things, it gives the following list of options to setup.exe:

Command Line Options:
 -A --disable-buggy-antivirus           Disable known or suspected buggy anti
                    virus software packages during execution.
 -C --categories                        Specify entire categories to install
 -D --download                          Download from internet
 -d --no-desktop                        Disable creation of desktop shortcut
 -h --help                              print help
 -K --pubkey                            Path to extra public key file (gpg format)
 -L --local-install                     Install from local directory
 -l --local-package-dir                 Local package directory
 -n --no-shortcuts                      Disable creation of desktop and start menu
                    shortcuts
 -N --no-startmenu                      Disable creation of start menu shortcut
 -O --only-site                         Ignore all sites except for -s
 -P --packages                          Specify packages to install
 -p --proxy                             HTTP/FTP proxy (host:port)
 -q --quiet-mode                        Unattended setup mode
 -r --no-replaceonreboot                Disable replacing in-use files on next
                    reboot.
 -R --root                              Root installation directory
 -S --sexpr-pubkey                      Extra public key in s-expr format
 -s --site                              Download site
 -U --keep-untrusted-keys               Use untrusted keys and retain all
 -u --untrusted-keys                    Use untrusted keys from last-extrakeys
 -X --no-verify                         Don't verify setup.ini signatures

So setup.exe -P <package name> should do the job. Don't have cygwin right here, so test it to confirm it works as expected.

To search for a package, per:

• http://cygwin.com/cygwin-ug-net/using-utils.html#cygcheck

you can use cygcheck -p:

  cygcheck -p REGEXP
  ...
  -p, --package-query  search for REGEXP in the entire cygwin.com package
                       repository (requires internet connectivity)

which produces output like (example from above site):

$ cygcheck -p 'libexpat.*\.a'
Found 2 matches for 'libexpat.*\.a'.

expat-1.95.7-1            XML parser library written in C
expat-1.95.8-1            XML parser library written in C

This performs an unattended upgrade of all Cygwin components for 64-bit:

cd C:\cygwin
wget -N https://cygwin.com/setup-x86_64.exe
setup-x86_64.exe --no-desktop --no-shortcuts --no-startmenu --quiet-mode

This performs an unattended upgrade of all cygwin components for 32-bit:

cd C:\cygwin
wget -N https://cygwin.com/setup-x86.exe
setup-x86.exe --no-desktop --no-shortcuts --no-startmenu --quiet-mode

You should reboot after the upgrade is completed to prevent Cygwin apps from misbehaving due to upgraded cygwin1.dll.

• --no-desktop Disable creation of desktop shortcut
• --no-shortcuts Disable creation of desktop and start menu
• --no-startmenu Disable creation of start menu shortcut
• --quiet-mode Unattended setup mode

An alternate solution would be to use the apt-cyg script available on GitHub.

The location for Cygwin's setup seems to have changes and split. Now you need either

wget http://cygwin.com/setup-x86.exe

or

wget http://cygwin.com/setup-x86_64.exe

The installer allows it from command line (elevated shell, please):

setup-x86.exe --root c:\cygwin -q --upgrade-also

for 64 bits version:

setup-x86_64.exe --root c:\cygwin -q --upgrade-also

Details:

• Replace c:\cygwin with your CygWin's root installation directory.
• Suggested to close any CygWin shell or program (i.e: net stop sshd if you installed OpenSSH).
• The parameter -q is not mandatory.

Works via GUI (DOS shell) or even on remote console (SSH or telnet). Not tested on PowerShell (someone did?).

Example of correct updating output:

G:\Instalac\CygWin\v2.852>Starting cygwin install, version 2.852
User has backup/restore rights
Current Directory: g:\Instalac\CygWin\Packages
Could not open service McShield for query, start and stop. McAfee may not be installed, or we don't have access.
root: c:\cygwin system
Selected local directory: g:\Instalac\CygWin\Packages
net: Direct
Loaded cached mirror list
get_url_to_membuf http://cygwin.com/mirrors.lst
getUrlToStream http://cygwin.com/mirrors.lst
site: http://ftp.hawo.stw.uni-erlangen.de/cygwin/
get_url_to_membuf http://ftp.hawo.stw.uni-erlangen.de/cygwin/x86/setup.bz2
getUrlToStream http://ftp.hawo.stw.uni-erlangen.de/cygwin/x86/setup.bz2
get_url_to_membuf http://ftp.hawo.stw.uni-erlangen.de/cygwin/x86/setup.bz2.sig
getUrlToStream http://ftp.hawo.stw.uni-erlangen.de/cygwin/x86/setup.bz2.sig
Changing gid back to original
Visited: 122 nodes out of 4415 while creating dependency order.
Dependency order of packages: _autorebase base-cygwin cygwin _update-info-dir libgcc1 libiconv2 libintl8 alternatives libattr1 li
bgmp10 coreutils libstdc++6 terminfo libncursesw10 libreadline7 bash findutils sed base-files libuuid1 libblkid1 libsmartcols1 zl
ib0 util-linux bashdb zlib-devel binutils libbz2_1 bzip2 libffi6 libp11-kit0 libtasn1_6 p11-kit p11-kit-trust ca-certificates cry
pt libmpfr4 gawk editrights libpcre1 grep libsigsegv2 diffutils csih cygrunsrv popt libpopt0 cygutils cygwin-devel dash file liba
tomic1 libcloog-isl4 libgomp1 libisl10 libmpc3 libquadmath0 libssp0 w32api-headers w32api-runtime windows-default-manifest gcc-co
re libexpat1 liblzma5 libdb4.8 libgdbm4 libopenssl100 libsqlite3_0 libcharset1 libiconv libintl-devel libuuid-devel python gdb li
bargp getent groff gzip hostname info ipc-utils libncurses10 less libapr1 libiodbc2 libmysqlclient18 libcom_err2 libkrb5support0
libk5crypto3 libkrb5_3 libgssapi_krb5_2 libsasl2_3 libopenldap2_4_2 perl openssl libpq5 libaprutil1 libedit0 libproxy1 libneon27
libpipeline1 libserf1_0 login lynx make man-db mintty nano ncurses openssh procps psmisc rebase run screen subversion xz tar tzco
de vim-minimal which zsh
Changing gid to Administrators
Ending cygwin install

If, during update, you had issues like these:

The following DLLs couldn't be rebased due to errors:
  /usr/bin/cygcrypt-0.dll

or:

The following DLLs couldn't be rebased because they were in use:
  /usr/bin/cygcrypt-0.dll

or:

ReBaseImage (/usr/bin/cygcrypt-0.dll) failed with last error = 6

...then you must rebase after installation:

1.- Close all CygWin shell, programs and services.
2.- Open c:\CygWin\bin\ash.exe as admin (elevated).
3.- Run /bin/rebaseall.