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28 .\" @(#)core.5 8.3 (Berkeley) 12/11/93
35 .Nd memory image file format
39 A small number of signals which cause abnormal termination of a process
40 also cause a record of the process's in-core state to be written
41 to disk for later examination by one of the available debuggers.
44 This memory image is written to a file named by default
46 in the working directory;
47 provided the terminated process had write permission in the directory,
48 and provided the abnormality did not cause
50 (In this event, the decision to save the core file is arbitrary, see
53 The maximum size of a core file is limited by the
57 Files which would be larger than the limit are not created.
59 With a large limit, a process that had mapped a very large,
60 and perhaps sparsely populated, virtual memory region, could take
61 a very long time to create core dumps.
62 The system ignores all signals sent to a process writing a core file, except
64 which terminates the writing and causes immediate exit of the process.
67 can be disabled by setting tunable
70 .Va kern.core_dump_can_intr
73 The name of the file is controlled via the
77 The contents of this variable describes a filename to store
79 This filename can be absolute, or relative (which
80 will resolve to the current working directory of the program
83 The following format specifiers may be used in the
85 sysctl to insert additional information into the resulting core
87 .Bl -tag -width "1234567890" -compact -offset "12345"
91 An index starting at zero until the sysctl
94 This can be useful for limiting the number of corefiles
95 generated by a particular process.
108 yielding the traditional
112 By default, a process that changes user or group credentials whether
113 real or effective will not create a corefile.
114 This behaviour can be
115 changed to generate a core dump by setting the
118 .Va kern.sugid_coredump
121 Corefiles can be compressed by the kernel if the following item
122 is included in the kernel configuration file:
123 .Bl -tag -width "1234567890" -compact -offset "12345"
128 The following sysctl control core file compression:
129 .Bl -tag -width "kern.compress_user_cores_level" -compact -offset "12345"
130 .It Em kern.compress_user_cores
131 Enable compression of user cores.
132 A value of 1 configures
135 and a value of 2 configures
138 Compressed core files will have a suffix of
142 appended to their filenames depending on the selected format.
143 .It Em kern.compress_user_cores_level
148 Corefiles are written with open file descriptor information as an ELF note.
149 By default, file paths are packed to only use as much space as needed.
150 However, file paths can change at any time, including during core dump,
151 and this can result in truncated file descriptor data.
153 All file descriptor information can be preserved by disabling packing.
154 This potentially wastes up to PATH_MAX bytes per open fd.
155 Packing is disabled with
156 .Dl sysctl kern.coredump_pack_fileinfo=0 .
158 Similarly, corefiles are written with vmmap information as an ELF note, which
160 By default, they are packed to only use as much space as
162 By the same mechanism as for the open files note, these paths can also
163 change at any time and result in a truncated note.
165 All vmmap information can be preserved by disabling packing.
166 Like the file information, this potentially wastes up to PATH_MAX bytes per
168 Packing is disabled with
169 .Dl sysctl kern.coredump_pack_vmmapinfo=0 .
171 In order to store all core images in per-user private areas under
177 .Dl sysctl kern.corefile=/var/coredumps/\&%U/\&%N.core
179 .Xr gdb 1 Pq Pa ports/devel/gdb ,
181 .Xr kgdb 1 Pq Pa ports/devel/gdb ,
188 file format appeared in