protocol for transmitting kernel dumps to a remote server
To compile netdump client support into the kernel, place the following line in
your kernel configuration file:
netdump is a UDP-based protocol for transmitting kernel dumps to a remote host.
A netdump client is a panicking kernel, and a netdump server is a host running
netdump daemon, available in ports as
clients are configured using the
utility or the
netdump command in
netdump client messages consist of a
fixed-size header followed by a variable-sized payload. The header contains
the message type, a sequence number, the offset of the payload data in the
kernel dump, and the length of the payload data (not including the header).
The message types are
netdump server messages have a fixed size and
contain only the sequence number of the client message. These messages
indicate that the server has successfully processed the client message with
the corresponding sequence number. All client messages are acknowledged this
way. Server messages are always sent to port 20024 of the client.
To initiate a
netdump, the client sends a
HERALD message to the server at port 20023. The
client may include a relative path in its payload, in which case the
netdump server should attempt to save the dump at
that path relative to its configured dump directory. The server will
HERALD using a random source port,
and the client must send all subsequent messages to that port.
EKCD_KEY message payloads contain the kernel
dump header, dump contents, and dump encryption key respectively. The offset
in the message header should be treated as a seek offset in the
corresponding file. There are no ordering requirements for these
netdump is completed by sending the
FINISHED message to the server.
The following network drivers support netdump:
The following variables are available as both
- Control debug message verbosity. Debug messages are disabled by default,
but are useful when troubleshooting or when developing driver
- Specify a path relative to the server's dump directory in which to store
the dump. For example, if the
netdump server is
configured to store dumps in /var/crash, a path of
“foo” will cause the server to attempt to store dumps from
the client in /var/crash/foo. The server will not
automatically create the relative directory.
- The client will poll the configured network interface while waiting for
acknowledgements. This parameter controls the maximum number of poll
attempts before giving up, which typically results in a re-transmit. Each
poll attempt takes 0.5ms.
- The number of times the client will re-transmit a packet before aborting a
dump due to a lack of acknowledgement. The default may be too small in
environments with lots of packet loss.
- The number of times the client will attempt to learn the MAC address of
the configured gateway or server before giving up and aborting the
netdump client support first appeared in
Only IPv4 is supported.
netdump may only be used after the kernel