Oracle Solaris Tunable Parameters Reference Manual

mdb Command

Starting with the Solaris 8 release is the modular debugger, mdb, is unique among Solaris debuggers because it is easily extensible. A programming API is available that allows compilation of modules to perform desired tasks within the context of the debugger.

mdb also includes a number of desirable usability features, including command-line editing, command history, built-in output pager, syntax checking, and command pipelining. mdb is the recommended post-mortem debugger for the kernel.

For more information, see mdb(1).

Example—Using mdb to Change a Value

To change the value of the integer parameter maxusers from 495 to 512, do the following:

# mdb -kw
Loading modules: [ unix krtld genunix ip logindmux ptm nfs ipc lofs ]
> maxusers/D
maxusers:       495
> maxusers/W 200
maxusers:       0x1ef           =       0x200
> $q

Replace maxusers with the actual address of the item to be changed, as well as the value the parameter is to be set to.

For more information on using the modular debugger, see the Solaris Modular Debugger Guide.

When using either kmdb or mdb debugger, the module name prefix is not required. After a module is loaded, its symbols form a common name space with the core kernel symbols and any other previously loaded module symbols.

For example, ufs:ufs_WRITES would be accessed as ufs_WRITES in each debugger (assuming the UFS module is loaded). The ufs: prefix is required when set in the /etc/system file.