So I've already set up the server and project and submit work unit, the next step for me is to fetch the work from client(boinc manager), what I did is to run boincmgr in clientgui directory.
To add other projects in the lists is totally ok, but my project cannot be added.
after I type in the url/myproject_name, it lets me enter the user email and password, and then it fails with:
"Failed to add project"
(also, I'm able to access my project web page and manager web page)

Can anyone help?? I've been stuck for hours.

also, another question would be, how to compute the work unit you've updated with client.

When working with a client, you can often get useful information by enabling extra debug logging information. If you're using the GUI BOINC Manager, switch to 'Advanced View', and from the Options menu select 'Event Log options' (or Ctrl+Shift+F). If you're using the command line, make a cc_config.xml file, and read it in with boinccmd --read_cc_config.

Either way, your initial problem seems to be with communication with your server. Use the <http_debug> log flag for comms problems.

Go through the 'attach project' process again, and examine the log. The client should have requested the configuration file by issuing an RPC for 'get_project_config.php'. The debug log should indicate what went wrong: if it doesn't, try opening that file yourself in a web browser on the machine the client is running on. My guess is that it's a DNS or firewall issue.

Go through the 'attach project' process again, and examine the log.

On Linux he should start the client with <code>boinc --redirectio</code> then, or otherwise the output is only going into the terminal window which is truncated. With the --redirectio attribute you tell BOINC to log to the stdout and stderr log files. (And this was glaringly missing from the documentation, so I added it).

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I tried to run clientgui/boincmgr --redirectio, it pops up the manager window as usual,
but seems there is no such option for manager, so I tried boincmgr --verbose, after this the manager says it cannot connect to core client...
I also tried to run client/boinc --redirectio (as a daemon? for boincmgr) then run clientgui/boincmgr, but still I got same question.
now I'm trying to redo the configure and make.

also, in event log, it says the url is invalid, but I can browse it in my browser, how could it be invalid?
(btw, my machine is ubuntu)
Thank you!

I tried to run clientgui/boincmgr --redirectio, it pops up the manager window as usual,
but seems there is no such option for manager, so I tried boincmgr --verbose, after this the manager says it cannot connect to core client...
I also tried to run client/boinc --redirectio (as a daemon? for boincmgr) then run clientgui/boincmgr, but still I got same question.
now I'm trying to redo the configure and make.

also, in event log, it says the url is invalid, but I can browse it in my browser, how could it be invalid?
(btw, my machine is ubuntu)
Thank you!

The invalid url is solved, it is because I didn't use ".", in my hostname, after I checked the source code...which is weird to me.
However, to connect to this Linux with my windows machine, it fails saying
"internet access ok - project servers may be temporarily down"... has anyone ever encountered this?

That is the standard configuration for BOINC. If project communication fails, BOINC tries to access a 'high availability server' (by default, google.com, but configurable) to try and determine whether it's a project server problem or a general comms problem. Nothing to worry about.