Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

In my dmesg this appeared when my window manager (xfwm4, part of XFCE) crashed:

xfwm4[3936]: segfault at 7f3c7c523770 ip 00007f3c7c523770 sp 00007ffffea1ee28 error 15 in SYSV00000000 (deleted)[7f3c7c4e8000+60000]

The same SYSV00000000 also appears in other places (like lsof). So, what is this SYSV00000000? I Googled around and found that it's related to virtual memory, but not much else.

share|improve this question
up vote 9 down vote accepted

The kernel is telling you that when the segfault occurred, the instruction pointer 0x7f3c7c523770 was in a SysV IPC shm segment. The shared memory segment started at 0x7f3c7c4e8000 and was 0x60000 bytes long.

SysV shm segments are not backed by a file, so the string SYSV00000000 appears where normally you'd get the filename of the executable or library where the segfault occurred. As a result this log line gives us no real useful information. If you want any hope of tracing the cause of the crash, you need the core dump.

I suspect that the instruction pointer wasn't supposed to be in there at all. It's pretty weird to load executable code into a SysV shm segment. But I haven't seen any XFCE code, so what looks weird to me might be normal there.

You can learn the basics about sysv shm, assuming you have a decent grasp of the basics of memory management by reading these man pages:

man svipc
man shmget
man shmat

Run the ipcs command to see what sysv ipc resources are currently allocated. ipcs -m limits the list to just the shared memory segments.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.