Remote Debugging

From Free Pascal wiki
Revision as of 13:47, 18 November 2014 by BigChimp (talk | contribs)


Introduction

Remote debugging means you work on your local computer and you want to start and debug a program on another computer, the remote machine. In the following examples the name of the local computer is 'localcomp' and the name of the remote computer is 'remotecomp'.

Note-icon.png

Note: Remote debugging will only work if the gdb supports async mode (see gdb doc for "set target async"). GDBServer usually does. GDB does for some targets only. In some cases gdb/gdbserver does support it, but not if "mi" mode is used (used by the IDE. A workaround for this must yet be implemented in the IDE.
IF async mode is not supported, or not for "mi" then:

  • It is currently not possible to use the "Pause" function to interrupt the running application.
  • It is not possible to modify break-/watch-points, while the application in the debugger is running.
  • One should no switch editor tabs, or open/close units, while the application in the debugger is running.
The 2nd and 3rd can be done, if the app in the debugger is paused. The only way for the app to become paused is by reaching a breakpoint that was set before the app was run.

Using SSH (Secure Shell)

SSH (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. It provides secure encrypted communications between two untrusted hosts over an insecure network. X11 connections and arbitrary TCP/IP ports can also be forwarded over the secure channel.

See the SSH man page for details. This text only covers SSH protocol 2. For differences for protocol 1 see the SSH man page.

Requirements for Lazarus

You must be able to log in via ssh to the remote machine (the computer where the program will run). This means the remote machine has an installed and running SSH server and you have an account allowed to login from your local machine (the computer where the Lazarus IDE is running).

You can test this by doing:

  
ssh username@remotecomp ls -la

This will create an SSH connection to 'remotecomp' with the username 'username'. After authentication it will print out a directory listing and return.

Configuring SSH

The IDE needs an SSH connection that does not prompt for a password. There are a lot of possibilities to achieve this. This text only describes a few. For security reasons it is strongly recommended that you read the SSH manpage.

Solution 1: User based authentication.

This will allow one specific user on the local computer to establish an SSH connection to the remote computer as a specific user without prompting for passwords.

ToDo: describe the server settings. On redhat this works without any change.
Step 1
create the public and private keys on the local machine

This will create two files on the local machine:

 ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub

If you already have these files, skip this step.

 
ssh-keygen -t rsa

Keep the default and leave the passphrase empty.

Step 2
copy the public key of the local machine to the remote machine
  
scp ~/.ssh/id_rsa.pub user@remotecomp:remote.pub
Step 3
create the file ~/.ssh/authorized_keys2 on the remote machine
  
ssh user@remotecomp
touch ~/.ssh/authorized_keys2
chmod 600 ~/.ssh/authorized_keys2

The chmod will set the permissions to only allow yourself to read the file. SSH requires this.

  
cat remote.pub >> ~/.ssh/authorized_keys2
rm remote.pub
exit
Step 4
test

You should now be able to login without password.

  
ssh user@remotecomp
Step 5
Setup the ssh debugger in the IDE

ToDo


Step 6
Set "Run parameters"

For remote debug we need to set the correct value for "Host application", "Command line parameters" and "Working directory". Remember: It is remote!

remote debug run parameters.png

Step 7
Set "Debugger parameters"

Select "Debugger type and path" to "GNU Debugger trough SSH(ssh)"

remote debug debuger parameters.png ToDo

Using gdbserver

See