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28 .\" @(#)core.5 8.3 (Berkeley) 12/11/93
36 .Nd memory image file format
40 A small number of signals which cause abnormal termination of a process
41 also cause a record of the process's in-core state to be written
42 to disk for later examination by one of the available debuggers.
45 This memory image is written to a file named by default
47 in the working directory;
48 provided the terminated process had write permission in the directory,
49 and provided the abnormality did not cause
51 (In this event, the decision to save the core file is arbitrary, see
54 The maximum size of a core file is limited by the
58 Files which would be larger than the limit are not created.
60 With a large limit, a process that had mapped a very large,
61 and perhaps sparsely populated, virtual memory region, could take
62 a very long time to create core dumps.
63 The system ignores all signals sent to a process writing a core file, except
65 which terminates the writing and causes immediate exit of the process.
68 can be disabled by setting tunable
71 .Va kern.core_dump_can_intr
74 The name of the file is controlled via the
78 The contents of this variable describes a filename to store
80 This filename can be absolute, or relative (which
81 will resolve to the current working directory of the program
84 The following format specifiers may be used in the
86 sysctl to insert additional information into the resulting core
88 .Bl -tag -width "1234567890" -compact -offset "12345"
92 An index starting at zero until the sysctl
95 This can be useful for limiting the number of corefiles
96 generated by a particular process.
109 yielding the traditional
113 By default, a process that changes user or group credentials whether
114 real or effective will not create a corefile.
115 This behaviour can be
116 changed to generate a core dump by setting the
119 .Va kern.sugid_coredump
122 Corefiles can be compressed by the kernel if the following item
123 is included in the kernel configuration file:
124 .Bl -tag -width "1234567890" -compact -offset "12345"
129 The following sysctl control core file compression:
130 .Bl -tag -width "kern.compress_user_cores_level" -compact -offset "12345"
131 .It Em kern.compress_user_cores
132 Enable compression of user cores.
133 A value of 1 configures
136 and a value of 2 configures
139 Compressed core files will have a suffix of
143 appended to their filenames depending on the selected format.
144 .It Em kern.compress_user_cores_level
149 Corefiles are written with open file descriptor information as an ELF note.
150 By default, file paths are packed to only use as much space as needed.
151 However, file paths can change at any time, including during core dump,
152 and this can result in truncated file descriptor data.
154 All file descriptor information can be preserved by disabling packing.
155 This potentially wastes up to PATH_MAX bytes per open fd.
156 Packing is disabled with
157 .Dl sysctl kern.coredump_pack_fileinfo=0 .
159 Similarly, corefiles are written with vmmap information as an ELF note, which
161 By default, they are packed to only use as much space as
163 By the same mechanism as for the open files note, these paths can also
164 change at any time and result in a truncated note.
166 All vmmap information can be preserved by disabling packing.
167 Like the file information, this potentially wastes up to PATH_MAX bytes per
169 Packing is disabled with
170 .Dl sysctl kern.coredump_pack_vmmapinfo=0 .
172 In order to store all core images in per-user private areas under
178 .Dl sysctl kern.corefile=/var/coredumps/\&%U/\&%N.core
180 .Xr gdb 1 Pq Pa ports/devel/gdb ,
182 .Xr kgdb 1 Pq Pa ports/devel/gdb ,
189 file format appeared in