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33 .Nd memory image file format
37 A small number of signals which cause abnormal termination of a process
38 also cause a record of the process's in-core state to be written
39 to disk for later examination by one of the available debuggers.
42 This memory image is written to a file named by default
44 in the working directory;
45 provided the terminated process had write permission in the directory,
46 and provided the abnormality did not cause
48 (In this event, the decision to save the core file is arbitrary, see
51 The maximum size of a core file is limited by the
55 Files which would be larger than the limit are not created.
57 With a large limit, a process that had mapped a very large,
58 and perhaps sparsely populated, virtual memory region, could take
59 a very long time to create core dumps.
60 The system ignores all signals sent to a process writing a core file, except
62 which terminates the writing and causes immediate exit of the process.
65 can be disabled by setting tunable
68 .Va kern.core_dump_can_intr
71 The name of the file is controlled via the
75 The contents of this variable describes a filename to store
77 This filename can be absolute, or relative (which
78 will resolve to the current working directory of the program
81 The following format specifiers may be used in the
83 sysctl to insert additional information into the resulting core
85 .Bl -tag -width "1234567890" -compact -offset "12345"
89 An index starting at zero until the sysctl
92 This can be useful for limiting the number of corefiles
93 generated by a particular process.
106 yielding the traditional
110 By default, a process that changes user or group credentials whether
111 real or effective will not create a corefile.
112 This behaviour can be
113 changed to generate a core dump by setting the
116 .Va kern.sugid_coredump
119 Corefiles can be compressed by the kernel if the following item
120 is included in the kernel configuration file:
121 .Bl -tag -width "1234567890" -compact -offset "12345"
126 The following sysctl control core file compression:
127 .Bl -tag -width "kern.compress_user_cores_level" -compact -offset "12345"
128 .It Em kern.compress_user_cores
129 Enable compression of user cores.
130 A value of 1 configures
133 and a value of 2 configures
136 Compressed core files will have a suffix of
140 appended to their filenames depending on the selected format.
141 .It Em kern.compress_user_cores_level
146 Corefiles are written with open file descriptor information as an ELF note.
147 By default, file paths are packed to only use as much space as needed.
148 However, file paths can change at any time, including during core dump,
149 and this can result in truncated file descriptor data.
151 All file descriptor information can be preserved by disabling packing.
152 This potentially wastes up to PATH_MAX bytes per open fd.
153 Packing is disabled with
154 .Dl sysctl kern.coredump_pack_fileinfo=0 .
156 Similarly, corefiles are written with vmmap information as an ELF note, which
158 By default, they are packed to only use as much space as
160 By the same mechanism as for the open files note, these paths can also
161 change at any time and result in a truncated note.
163 All vmmap information can be preserved by disabling packing.
164 Like the file information, this potentially wastes up to PATH_MAX bytes per
166 Packing is disabled with
167 .Dl sysctl kern.coredump_pack_vmmapinfo=0 .
169 In order to store all core images in per-user private areas under
171 (assuming the appropriate subdirectories exist and are writable by users),
176 .Dl sysctl kern.corefile=/var/coredumps/\&%U/\&%N.core
178 .Xr gdb 1 Pq Pa ports/devel/gdb ,
180 .Xr kgdb 1 Pq Pa ports/devel/gdb ,
187 file format appeared in