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Man Pages

Manual Reference Pages  -  PENCTL (1)


penctl - control a running pen load balancer


See Also


penctl host:port|/path/to/socket command


penctl lbhost:8888 roundrobin

Turns off client tracking on the load balancer running on lbhost.

penctl /var/run/pen/tmp/ctrl status

Prints status information in html format.


Penctl connects to the optional control socket on a pen load balancer. It reads commands from the command line, performs minimal syntax checking and sends them to pen. Replies, if any, are printed on stdout.

The program can also be used through the cgi script penctl.cgi, which allows pen to be controlled from any web browser.


  Specifies a control port where the load balancer listens for commands.


  Call abort() when a fatal error is encountered. This will create a core file which allows further troubleshooting. Disabled by default.
no abort_on_error
  Exit normally on fatal error with an error code which indicates failure.
acl N permit|deny sourceip4 [mask]
  Adds an entry to access list N, where N is a number from 0 to 9. The source and mask addresses are in the usual dotted quad notation. If mask is omitted, it defaults to

acl N permit|deny sourceip6[/length]
  If the source address contains the character ’:’, the address is interpreted as IPv6. Unlike IPv4 access entries, a length is used to indicate the mask. If length is omitted, it defaults to 128.

acl N permit|deny country NN
  If the source address is the special word "country", a two-letter country code can be used to restrict access to the load balancer. For this to work, pen must be built with geoip support.
no acl N
  Deletes all entries from access list N. The resulting access list permits all traffic.
ascii Communication dumps in ascii format (cf option -a).
no ascii
  Communication dumps in hex format.
  Return current blacklist time in seconds.
blacklist T
  Set the blacklist time in seconds.
block Do not make sockets nonblocking. This is obsolete as of 0.26.0 and does nothing.
no block
  Make sockets nonblocking.
client_acl N
  Check connecting clients against access list N (default 0).
clients_max [N]
  With argument, increase the maximum number of known clients. Returns max number of clients.
close N
  Close connection N
connection N
  Display some basic information about connection N.
conn_max [N]
  With argument, increase the max number of simultaneous connections. Returns max number.
  Return address and port where pen listens for control connections.
control_acl N
  Check accesses to the control port against access list N (default 0).
debug Return current debug level.
debug N
  Set debug level to N.
  Always wait for the next round of the main loop before forwarding data. Normally pen tries to do that immediately. This is obsolete as of 0.26.0 and does nothing.
no delayed_forward
  Try to forward data immediately, to avoid the overhead of copying it to a temporary buffer and waiting for the next main loop round.
dsr_if IF
  Use IF as the interface for Direct Server Return.
dummy Act as a dummy web server with very limited functionality but high performance. Only useful for testing. Disabled by default.
no dummy
  Do not act as a dummy web server.
epoll Use epoll for event management (Linux). This is the default on Linux.
exit Exit. Only available if pen was started with the -X option.
hash Use a hash on the client IP address for initial server selection.
no hash
  Do not use a hash.
http Add X-Forwarded-For headers to http requests.
no http
  Do not add X-Forwarded-For headers.
idle_timeout N
  Close connections that have been inactive for N seconds. Default 0 = never close.
idlers [N]
  Create N reliable idle connections to the backend servers. Without argument, display the current/requested number of reliable idlers.
include FILE
  Read commands from file.
kqueue Use kqueue for event management (FreeBSD, NetBSD, OpenBSD). This is the default on the systems that have it.
listen Return local address and port pen listens to for incoming client connections.
listen [address:]:port
  Close the listening socket and reopen using specified address (optional) and port.
log Show where pen is logging, if anywhere.
log FILE
  Log to FILE.
mode Write a summary of the current mode of operation. The listed modes are block, delayed_forward, hash, roundrobin, stubborn.
no log Turn off logging.
pending_max N
  Max allowed number of pending nonblocking connections. Default 100, minimum 1.
pid Return the process id of the running daemon.
poll Use poll for event management.
prio Use the priority based algorithm.
no prio
  Do not use the priority based algorithm.
recent [N]
  Shows which clients have connected in the last N seconds (default 300).
  Use round-robin server selection without client tracking
no roundrobin

select Use select for event management.
server N [ acl A |´┐Żaddress A | port P | max M | hard H | blacklist T | weight W | prio P ]
  Change acl, address, port, weight, priority and/or max connections for server N, or blacklist it for T seconds.
  List address, port, weight, priority and max number of simultaneous connections for each remote server.
socket N
  Show to which connection socket N belongs.
ssl_ciphers CIPHERS
  Choose list of available SSL ciphers, specified in the format described in
ssl_client_renegotiation_interval S
  Allowing the client to request renegotiation is a potential denial of service vector. This command specifies the minimum number of seconds the client has to wait between requests for renegotiation requests. Default 3600 = effectively disabled.
ssl_ocsp_response FILENAME
  Specifies the location of a file containing a pre-fetched OCSP response. The file must be refreshed regularly by a cron job or similar and the ssl_ocsp_response command repeated to make Pen re-read the file..
ssl_option OPTION
  Manipulate SSL options. The available options are no_sslv2, no_sslv3, no_tlsv1, no_tlsv1.1, no_tlsv1.2, cipher_server_preference. Use the command multiple times to specify multiple options.
ssl_sni_path PATH
  This command enables the Server Name Indication TLS extension by specifying a directory where domain.key, domain.crt and files can be found.
status Print status information in html format.
  If the initial server selection is unavailable, close the client connection without trying another
no stubborn
tarpit_acl [N]
  Used in DSR mode. If N is an existing access list, Pen will reply to ARP requests for IP addresses that match the access list, and reply with SYN+ACK to TCP SYN requests to these addresses. The result is that someone trying to scan a network will be slowed down by a large number of false positives.
tcp_fastclose up|down|both|off
  Close both sockets to upstream and downstream if one of them closes theirs. Default = off.
  Set TCP_NODELAY on sockets, effectively turning off the Nagle algorithm.
no tcp_nodelay
  Do not set TCP_NODELAY on sockets. This is the default.
  Return current connect timeout in seconds.
timeout N
  Set connect timeout to N seconds.
tracking N
  Set tracking time, i.e. how long clients will be remembered. The default 0 will never expire clients based on time.
  On compatible platforms, use the client’s address as source address in the connection to the backend server.
no transparent
  Use Pen’s address as source address in the connection to the backend server.
  Return file name of html status reports, if any.
web_stats FILE
  Set the name of html status reports.
no web_stats
  Do not generate html status reports.
weight Use weight for server selection.
no weight
  Do not use weight for server selection.
write [FILE]
  Write the current configuration into a file which can be used to start pen. If FILE is omitted, the configuration is written into pen’s original configuration file.




Copyright (C) 2002-2015 Ulric Eriksson, <>.
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