Docs: Fix gdb pretty printers

fixes #8048

doc/3-troubleshooting.md

@@ -262,7 +262,7 @@ so please make sure to update the installation paths accordingly (`pwd`).
 
 Boost Pretty Printers:
 
-    $ mkdir ~/.gdb_printers && cd ~/.gdb_printers
+    $ mkdir -p ~/.gdb_printers && cd ~/.gdb_printers
     $ git clone https://github.com/ruediger/Boost-Pretty-Printer.git && cd Boost-Pretty-Printer
     $ pwd
     /home/michi/.gdb_printers/Boost-Pretty-Printer
@@ -274,24 +274,18 @@ Python Pretty Printers:
 
 Icinga 2 Pretty Printers:
 
-    $ mkdir -p ~/.gdb_printers/icinga2 && ~/.gdb_printers/icinga2
+    $ mkdir -p ~/.gdb_printers/icinga2 && cd ~/.gdb_printers/icinga2
     $ wget https://raw.githubusercontent.com/Icinga/icinga2/master/tools/debug/gdb/icingadbg.py
 
 Now you'll need to modify/setup your `~/.gdbinit` configuration file.
 You can download the one from Icinga 2 and modify all paths.
 
-> **Note**
->
-> The path to the `pthread` library varies on distributions. Use
-> `find /usr/lib* -type f -name '*libpthread.so*'` to get the proper
-> path.
-
 Example on Fedora 20 x64:
 
     $ wget https://raw.githubusercontent.com/Icinga/icinga2/master/tools/debug/gdb/gdbinit -O ~/.gdbinit
     $ vim ~/.gdbinit
 
-    set env LD_PRELOAD /usr/lib64/libpthread.so
+    set print pretty on
 
     python
     import sys
@@ -314,7 +308,11 @@ Example on Fedora 20 x64:
     register_printer_gen(None)
     end
 
+If you are getting the following error when running gdb, the `libstdcxx`
+printers are already preloaded in your environment and you can remove
+the duplicate import in your `~/.gdbinit` file.
 
+    RuntimeError: pretty-printer already registered: libstdc++-v6
 
 ### <a id="development-debug-gdb-run"></a> GDB Run
 

tools/debug/gdb/gdbinit

@@ -1,4 +1,4 @@
-set env LD_PRELOAD /lib/x86_64-linux-gnu/libpthread.so.0
+set print pretty on
 
 python
 import sys