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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
56 Files which would be larger than the limit are not created.
58 The name of the file is controlled via the
62 The contents of this variable describes a filename to store
64 This filename can be absolute, or relative (which
65 will resolve to the current working directory of the program
68 The following format specifiers may be used in the
70 sysctl to insert additional information into the resulting core file
72 .Bl -tag -width "1234567890" -compact -offset "12345"
76 An index starting at zero until the sysctl
79 This can be useful for limiting the number of corefiles
80 generated by a particular process.
91 yielding the traditional
95 By default, a process that changes user or group credentials whether
96 real or effective will not create a corefile.
98 changed to generate a core dump by setting the
101 .Va kern.sugid_coredump
104 Corefiles can be compressed by the kernel if the following item
105 is included in the kernel configuration file:
106 .Bl -tag -width "1234567890" -compact -offset "12345"
111 When the GZIO option is included, the following sysctls control whether core
112 files will be compressed:
113 .Bl -tag -width "kern.compress_user_cores_gzlevel" -compact -offset "12345"
114 .It Em kern.compress_user_cores_gzlevel
115 Gzip compression level.
117 .It Em kern.compress_user_cores
118 Actually compress user cores.
119 Compressed core files will have a suffix of
124 Corefiles are written with open file descriptor information as an ELF note.
125 By default, file paths are packed to only use as much space as needed.
126 However, file paths can change at any time, including during core dump,
127 and this can result in truncated file descriptor data.
129 All file descriptor information can be preserved by disabling packing.
130 This potentially wastes up to PATH_MAX bytes per open fd.
131 Packing is disabled with
132 .Dl sysctl kern.coredump_pack_fileinfo=0 .
134 Similarly, corefiles are written with vmmap information as an ELF note, which
136 By default, they are packed to only use as much space as
138 By the same mechanism as for the open files note, these paths can also
139 change at any time and result in a truncated note.
141 All vmmap information can be preserved by disabling packing.
142 Like the file information, this potentially wastes up to PATH_MAX bytes per
144 Packing is disabled with
145 .Dl sysctl kern.coredump_pack_vmmapinfo=0 .
147 In order to store all core images in per-user private areas under
153 .Dl sysctl kern.corefile=/var/coredumps/\&%U/\&%N.core
163 file format appeared in