I installed a program , at the end of the installation EULA document opened after reading , not knowing how to close it i clicked on 'x' at the top right. on installing another software i gpt the following error.

E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)

E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?

i tried to trace the cause of the error ,

root@jolicloud:~$ strace -c echo

% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
-nan 0.000000 0 3 read
-nan 0.000000 0 1 write
-nan 0.000000 0 30 13 open
-nan 0.000000 0 19 close
-nan 0.000000 0 1 execve
-nan 0.000000 0 3 3 access
-nan 0.000000 0 3 brk
-nan 0.000000 0 3 munmap
-nan 0.000000 0 4 mprotect
-nan 0.000000 0 21 mmap2
-nan 0.000000 0 18 fstat64
-nan 0.000000 0 1 set_thread_area
------ ----------- ----------- --------- --------- ----------------
100.00 0.000000 107 16 total


what do i do next ?

There is still another instance running.
Find and kill it using the
ps ax an kill command.
If this doesn't work, look for the lockfile and delete it.

Kind regards

how do i look for the lock file please help.which folder or any command.