231 lines
9.3 KiB
Plaintext
231 lines
9.3 KiB
Plaintext
What is Cygserver?
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Cygserver is a program which is designed to run as a background service.
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It provides Cygwin applications with services which require security
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arbitration or which need to persist while no other cygwin application
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is running.
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The implemented services so far are:
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- Control slave tty/pty handle dispersal from tty owner to other
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processes without compromising the owner processes' security.
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- XSI IPC Message Queues.
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- XSI IPC Semaphores.
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- XSI IPC Shared Memory.
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- Allows non-privileged users to store obfuscated passwords in the
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registry to be used for setuid(2) to create user tokens with network
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credentials. This service is used by `passwd -R'. Using the stored
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passwords in setuid(2) does not require running cygserver. The
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registry storage is the same as Windows uses to store passwords for
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accounts running Windows services.
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Cygserver command line options:
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Options to Cygserver take the normal UNIX-style `-X' or `--longoption' form.
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Nearly all options have a counterpart in the configuration file (see below)
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so setting them on the command line isn't really necessary. Command line
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options override settings from the Cygserver configuration file.
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The one-character options are prepended by a single dash, the long variants
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are prepended with two dashes. Arguments to options are marked in angle
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brackets below. These are not part of the actual syntax but are used only to
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denote the arguments. Note that all arguments are required. Cygserver
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has no options with optional arguments.
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The options recognized are:
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-f, --config-file <file>
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Use <file> as configuration file instead of the default configuration
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line. The default configuration file is /etc/cygserver.conf, typically.
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The --help and --version options will print the default configuration
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pathname.
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This option has no counterpart in the configuration file, for obvious
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reasons.
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-c, --cleanup-threads <num>
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Number of threads started to perform cleanup tasks. Default is 2.
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Configuration file option: kern.srv.cleanup_threads
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-r, --request-threads <num>
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Number of threads started to serve application requests. Default is 10.
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The -c and -r options can be used to play with Cygserver's performance
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under heavy load conditions or on slow machines.
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Configuration file option: kern.srv.request_threads
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-p, --process-cache <num>
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Number of processes which can connect concurrently to cygserver.
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Default is 62. Each process connected to cygserver is a synchronization
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object which has to be maintained. The data structure to maintain these
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processes is the so-called "process cache". In theory, an arbitrary
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number of processes could connect to cygserver, but due to the need to
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synchronize, the higher the number of connected processes, the more
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synchronization overhead exists. By using this option, you can set an
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upper limit to the synchronization effort. If more than 62 processes
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try to connect to cygserver concurrently, two additional synchronization
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threads are necessary, and one for each further 62 concurrent
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processes. So, useful values for the --process-cache option are 62, 124,
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186, 248, 310. 310 is the maximum value.
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Configuration file option: kern.srv.process_cache_size
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NOTE: The number of child processes of a single parent process is limited
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to 256. So in case of taking advantage of a process cache size beyond 256,
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keep in mind that not all of these processes can be child processes of one
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single parent process.
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-d, --debug
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Log debug messages to stderr. These will clutter your stderr output with
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a lot of information, typically only useful to developers.
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-e, --stderr
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Force logging to stderr. This is the default if stderr is connected to
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a tty. Otherwise, the default is logging to the system log. By using
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the -e, -E, -y, -Y options (or the appropriate settings in the
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configuration file), you can explicitely set the logging output as you
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like, even to both, stderr and syslog.
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Configuration file option: kern.log.stderr
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-E, --no-stderr
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Don't log to stderr. Configuration file option: kern.log.stderr
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-y, --syslog
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Force logging to the system log. This is the default, if stderr is not
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connected to a tty, e. g. redirected to a file.
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-Y, --no-syslog
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Don't log to syslog. Configuration file option: kern.log.syslog
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-l, --log-level <level>
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Set the verbosity level of the logging output. Valid values are between
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1 and 7. The default level is 6, which is relatively chatty. If you set
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it to 1, you will get only messages which are printed under severe conditions,
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which will result in stopping Cygserver itself.
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Configuration file option: kern.log.level
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-m, --no-sharedmem
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Don't start XSI IPC Shared Memory support. If you don't need XSI IPC
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Shared Memory support, you can switch it off here.
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Configuration file option: kern.srv.sharedmem
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-q, --no-msgqueues
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Don't start XSI IPC Message Queues.
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Configuration file option: kern.srv.msgqueues
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-s, --no-semaphores
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Don't start XSI IPC Semaphores.
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Configuration file option: kern.srv.semaphores
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-S, --shutdown
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Shutdown a running daemon and exit. Other methods are sending a SIGHUP
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to the Cygserver PID or, if running as service under NT, calling
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`net stop cygserver' or `cygrunsrv -E cygserver'.
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-h, --help
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Output usage information and exit.
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-v, --version
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Output version information and exit.
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How to start Cygserver:
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Before you run Cygserver for the first time, you should run the
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/usr/bin/cygserver-config script once. It creates the default
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configuration file and, upon request, installs Cygserver as service
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when running under NT. The script only performs a default install,
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with no further options given to Cygserver when running as service.
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Due to the wide configurability by changing the configuration file,
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that's typically not necessary.
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It's best practice to run Cygserver as a service under LocalSystem
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account. This is the way it is installed for you by the
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/usr/bin/cygserver-config script.
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How to use the Cygserver services:
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The Cygserver services are used by Cygwin applications only if you
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set the environment variable CYGWIN to contain the string "server".
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You must do this before starting the application.
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Typically, you don't need any other option, so it's ok to set CYGWIN
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just to "server". It is not necessary to set the CYGWIN environment
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variable prior to starting the Cygserver process itself, but it won't
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hurt to do so.
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The easiest way is to set the environment variable CYGWIN to the values
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you want in the Windows system environment and to reboot the machine.
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This is advisable, since it allows you to set the variable once and
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then forget about it. It also ensures that services as well as desktop
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applications have the same setting.
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If you don't want that for whatever reason, you can set the
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variable in the /cygwin.bat file which is used in the net distribution,
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to start a Cygwin bash from the desktop. In that file, you can set
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the CYGWIN variable using Windows command line interpreter syntax, e. g.:
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set CYGWIN=server
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If you don't set CYGWIN in the system environment, but you're running
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other Cygwin services, these services need to get that CYGWIN value by
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setting the environment using the appropriate cygrunsrv option '-e' when
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installing the service. Example installing a service 'foo':
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cygrunsrv -I foo -p /usr/sbin/foo -e "CYGWIN=server"
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The Cygserver configuration file:
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Cygserver has many options, which allow to customize the server
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to your needs. Customization is accomplished by editing the configuration
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file, which is by default /etc/cygserver.conf. This file is read only
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once on startup of Cygserver. There's no option to re-read the file on
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runtime by, say, sending a signal to Cygserver.
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The configuration file determines how Cygserver operates. There are
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options which set the number of threads running in parallel, options
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for setting how and what to log and options to set various maximum
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values for the IPC services.
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The default configuration file delivered with Cygserver is installed
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to /etc/defaults/etc. The /usr/bin/cygserver-config script copies it to
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/etc, giving you the option to overwrite an already existing file or to
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leave it alone. Therefore, the /etc file is safe to be changed by you,
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since it will not be overwritten by a later update installation.
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The default configuration file contains many comments which describe
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everything needed to understand the settings. A comment at the start of the
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file describes the syntax rules for the file. The default options are shown
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in the file but are commented out.
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It is generally a good idea to uncomment only options which you intend to
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change from the default values. Since reading the options file on Cygserver
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startup doesn't take much time, it's also considered good practice to keep
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all other comments in the file. This keeps you from searching for clues
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in other sources.
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If you have problems with Cygserver, or you have found a bug, or you
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think you have found a bug, or you don't understand configuration file
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options, the mailing list <cygwin@cygwin.com> is the right place to ask
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questions.
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Have fun!
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