DDB(8) BSD System Manager's Manual DDB(8)NAME
ddb -- configure DDB kernel debugger properties
SYNOPSIS
ddb capture [-M -core] [-N -system] print
ddb capture [-M -core] [-N -system] status
ddb script scriptname
ddb script scriptname=script
ddb scripts
ddb unscript scriptname
ddb pathname
DESCRIPTION
The ddb utility configures certain aspects of the ddb(4) kernel debugger from user space that are not configured at compile-time or easily
via sysctl(8) MIB entries.
To ease configuration, commands can be put in a file which is processed using ddb as shown in the last synopsis line. An absolute pathname
must be used. The file will be read line by line and applied as arguments to the ddb utility. Whitespace at the beginning of lines will be
ignored as will lines where the first non-whitespace character is '#'.
OUTPUT CAPTURE
The ddb utility can be used to extract the contents of the ddb(4) output capture buffer of the current live kernel, or from the crash dump of
a kernel on disk. The following debugger commands are available from the command line:
capture [-M core] [-N system] print
Print the current contents of the ddb(4) output capture buffer.
capture [-M core] [-N system] status
Print the current status of the ddb(4) output capture buffer.
SCRIPTING
The ddb utility can be used to configure aspects of ddb(4) scripting from user space; scripting support is described in more detail in
ddb(4). Each of the debugger commands is available from the command line:
script scriptname
Print the script named scriptname.
script scriptname=script
Define a script named scriptname. As many scripts contain characters interpreted in special ways by the shell, it is advisable to
enclose script in quotes.
scripts
List currently defined scripts.
unscript scriptname
Delete the script named scriptname.
EXIT STATUS
The ddb utility exits 0 on success, and >0 if an error occurs.
EXAMPLES
The following example defines a script that will execute when the kernel debugger is entered as a result of a break signal:
ddb script kdb.enter.break="show pcpu; bt"
The following example will delete the script:
ddb unscript kdb.enter.break
For further examples, see the ddb(4) and textdump(4) manual pages.
SEE ALSO ddb(4), textdump(4), sysctl(8)HISTORY
The ddb utility first appeared in FreeBSD 7.1.
AUTHORS
Robert N M Watson
BUGS
Ideally, ddb would not exist, as all pertinent aspects of ddb(4) could be configured directly via sysctl(8).
BSD December 24, 2008 BSD
Check Out this Related Man Page
TEXTDUMP(4) BSD Kernel Interfaces Manual TEXTDUMP(4)NAME
textdump -- textdump kernel dumping facility
SYNOPSIS
options KDB
options DDB
DESCRIPTION
The textdump facility allows the capture of kernel debugging information to disk in a human-readable rather than the machine-readable form
normally used with kernel memory dumps and minidumps. This representation, while less complete in that it does not capture full kernel
state, can provide debugging information in a more compact, portable, and persistent form than a traditional dump. By combining textdump
with other ddb(4) facilities, such as scripting and output capture, detailed bug information can be captured in a fully automated manner.
FORMAT
textdump data is stored in a dump partition in the same style as a regular memory dump, and will be automatically extracted by savecore(8) if
present on boot.
textdump files are stored in the tar(5) format, and consist of one or more text files, each storing a particular type of debugging output.
The following parts may be present:
ddb.txt Captured ddb(4) output, if the capture facility has been used. May be disabled by clearing the debug.ddb.textdump.do_ddb
sysctl.
config.txt Kernel configuration, if has been compiled into the kernel. May be disabled by clearing the debug.ddb.textdump.do_config
sysctl.
msgbuf.txt Kernel message buffer, including recent console output if the capture facility has been used. May be disabled by clearing the
debug.ddb.textdump.do_msgbuf sysctl.
panic.txt Kernel panic string, if the kernel panicked before the dump was generated. May be disabled by clearing the
debug.ddb.textdump.do_panic sysctl.
version.txt Kernel version string. My be disabled by clearing the debug.ddb.textdump.do_version sysctl.
Kernel textdumps may be extracted using tar(1).
CONFIGURATION
The textdump facility is enabled as part of the kernel debugger using options KDB and options DDB. By default, kernel dumps generated on
panic or via explicit requests for a dump will be regular memory dumps; however, by using the textdump set command in ddb(4), or by setting
the debug.ddb.textdump.pending sysctl to 1 using sysctl(8), it is possible to request that the next dump be a textdump.
If at the ddb(4) command line, the commands textdump set, textdump status, and textdump unset may be used to set, query, and clear the
textdump pending flag.
As with regular kernel dumps, a dump partition must be automatically or manually configured using dumpon(8).
EXAMPLES
In the following example, the script kdb.enter.panic will run when the kernel debugger is entered as a result of a panic, enable output cap-
ture, dump several useful pieces of debugging information, and then invoke panic in order to force a kernel dump to be written out followed
by a reboot:
script kdb.enter.panic=textdump set; capture on; show allpcpu; bt;
ps; alltrace; show alllock; call doadump; reset
In the following example, the script kdb.enter.witness will run when the kernel debugger is entered as a result of a witness violation,
printing lock-related information for the user:
script kdb.enter.witness=show locks
These scripts may also be configured using the ddb(8) utility.
SEE ALSO tar(1), ddb(4), tar(5), ddb(8), dumpon(8), savecore(8), sysctl(8)HISTORY
The textdump facility first appeared in FreeBSD 7.1.
AUTHORS
The textdump facility was created by Robert N. M. Watson.
BSD December 24, 2008 BSD