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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
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 The following sysctl control core file compression:
112 .Bl -tag -width "kern.compress_user_cores_level" -compact -offset "12345"
113 .It Em kern.compress_user_cores
114 Enable compression of user cores.
115 A value of 1 configures
118 and a value of 2 configures
121 Compressed core files will have a suffix of
125 appended to their filenames depending on the selected format.
126 .It Em kern.compress_user_cores_level
131 Corefiles are written with open file descriptor information as an ELF note.
132 By default, file paths are packed to only use as much space as needed.
133 However, file paths can change at any time, including during core dump,
134 and this can result in truncated file descriptor data.
136 All file descriptor information can be preserved by disabling packing.
137 This potentially wastes up to PATH_MAX bytes per open fd.
138 Packing is disabled with
139 .Dl sysctl kern.coredump_pack_fileinfo=0 .
141 Similarly, corefiles are written with vmmap information as an ELF note, which
143 By default, they are packed to only use as much space as
145 By the same mechanism as for the open files note, these paths can also
146 change at any time and result in a truncated note.
148 All vmmap information can be preserved by disabling packing.
149 Like the file information, this potentially wastes up to PATH_MAX bytes per
151 Packing is disabled with
152 .Dl sysctl kern.coredump_pack_vmmapinfo=0 .
154 In order to store all core images in per-user private areas under
160 .Dl sysctl kern.corefile=/var/coredumps/\&%U/\&%N.core
171 file format appeared in