You are here: TWiki> Online Web>WebHome (2022-03-29, NikoNeufeld)
create new tag
, view all tags

Welcome to the LHCb Online web

This web-site collects information for the operation of the LHCb Online system. More specifically for the central and shared Online services, which are used by all sub-detectors and which are required to run the entire experiment. If you are a new user in LHCb, a shifter or a piquet, this one is (should be) a good starting point.

The amount of material on this web is quite big and we are painfully aware that the structure is far from perfect. Work is in progress to improve this. Please be patient or even better: help.

The material on this top-page is of interest for any user of the Online system. In addition you will find here specialised sub-webs dedicated to System Administration (old), the Online on-call shifter: OnlinePiquet and R&D projects in Online computing by members of the Online team.

The User environment

This chapter is about getting an account, logging in, staying up-to-date, communicating with other users, how the Operating System environments are configured and much more.

Working from home

Since the LHCb Online network is not directly accessible from the internet working from home is not as straight forward as logging into CERN. Here we explain the recommended ways to access the Online system from outside. The minimum requirements are that you have a computer running Linux, Mac OS-X or Windows in a reasonably recent version, an internet connection and a valid CERN account, which allows you to login into lxplus.

The LHCb Online system has both Linux and Windows machines. On Linux tasks can often be achieved from the command line (ssh) alone, but some tasks, in particular PVSS panels require a graphical session. On Windows the possibilities of the command-line are severely limited (crippled some people would say) and for experts only, so graphical remote sessions are the only option. All these options from and to all OS-es will be explained here. The explanations here are sorted by the remote (i.e. home) operating system.

Understanding the system

The LHCb Online system consists of several large systems, which are intimately connected: the DataAcquisition (DAQ) with its private network, the ExperimentControlSystem, the HLTFarm, the OnlineMonitoring

Running your detector, LHCb or FEST

Working with the raw-data


"Everything which can go wrong, will go wrong"

Debugging problems in the Online system is not easy, but there are tools to help you. Here it is assumed that you have carefully checked any error-messages you might have on the PVSS panel (if used) and this did not help. The first step to a deeper under-standing are the logfiles written by most of the processes and the hardware devices in the system.

To see if (and where) you have a problem with data transmission, you can use the Data Flow Monitoring panel available in PVSS. It shows amounts of data sent/received and rates for your detector (or FEST/LHCb) at each stage of the DAQ system.

Crashes collector "CoreWatch"

Programs should never crash. Probably hevean's software is written that way. In LHCb you may use (or write youself) a code which sometimes crashes, reporting nothing to log files (if any). The crash collector CoreWatch External link mark (accessible only in LHCb network now, but this will change soon) will try to catch all such cases and record them to a DB. The web interface will give you access to all recorded crashes happend on LHCb computers. In addition you may debug most recent (last two weeks) "core" files produced by crashed programs.


More Stuff

Online Web Utilities

NikoNeufeld - 28 Apr 2011
Topic revision: r155 - 2022-03-29 - NikoNeufeld

This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2008-2022 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback