gdb failed opening pid

GNU gdb (Ubuntu/Linaro 7.2-1ubuntu11) 7.2
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program: No such file or directory.
Attaching to process 3385
Could not attach to process.  If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.
/home/benjamin/3385: No such file or directory.