strace may stop process Some versions of strace may leave the traced process in a stopped state when you stop tracing. Check if your strace command suffers from this bug as follows: $ sleep 100 & [1] 9400 $ strace -p $! Process 9400 attached - interrupt to quit restart_syscall(<... resuming interrupted call ...> <-- I pressed ^C here strace: ptrace(PTRACE_CONT,1,133): Input/output error Process 9400 detached $ grep ^State /proc/${!}/status State: T (stopped) $ kill -CONT $! $ grep ^State /proc/${!}/status State: S (sleeping) If you see the process you just ran strace on has a stopped state as shown above, immediately send a CONTinue signal to it. Otherwise unpredictable consequences could result. If you strace'd a critical Oracle background process, upon continuing the process, the Oracle instance is likely to crash. To correct it, update the strace package: $ rpm -qi strace #note the version and release Name : strace Relocations: (not relocatable) Version : 4.5.16 Vendor: Red Hat, Inc. Release : 1.el4_8.11 Build Date: Tue 08 Jun 2010 03:19:10 AM CDT ... $ sudo rpm -e strace Password: $ rpm -qi strace $ sudo up2date install strace #use yum instead of up2date on RHEL 5 ... Fetching rpm headers... ######################################## Name Version Rel Arch ---------------------------------------------------------------------------------------- strace 4.5.16 1.el4_8.11 x86_64 Testing package set / solving RPM inter-dependencies... ######################################## strace-4.5.16-1.el4_8.11.x8 ########################## Done. ... $ sleep 100 & [1] 23029 $ strace -p $! Process 23029 attached - interrupt to quit restart_syscall(<... resuming interrupted call ...> Process 23029 detached $ grep ^State /proc/${!}/status State: S (sleeping) Ref: https://www.redhat.com/archives/redhat-list/2009-October/msg00190.html