Ubuntu Manpage: netdump — protocol for transmitting kernel dumps to a remote server

Provided by: freebsd-manpages_12.2-1_all

NAME

       netdump — protocol for transmitting kernel dumps to a remote server

SYNOPSIS

       To  compile netdump client support into the kernel, place the following line in your kernel configuration
       file:

             options NETDUMP

DESCRIPTION

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 the netdump daemon, available in ports as
ports/ftp/netdumpd. netdump clients are configured using the dumpon(8) utility.

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 HERALD, FINISHED, KDH,
VMCORE, and EKCD_KEY. 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 acknowledge the HERALD using a
random source port, and the client must send all subsequent messages to that port.

The KDH, VMCORE, and 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 messages.

A netdump is completed by sending the FINISHED message to the server.

The following network drivers support netdump: alc(4), bge(4), bnxt(4), bxe(4), cxgb(4), em(4), igb(4),
ix(4), ixl(4), mlx4en(4), mlx5en(4), re(4), vtnet(4).

SYSCTL VARIABLES

The following variables are available as both sysctl(8) variables and loader(8) variables:

net.netdump.debug
Control debug message verbosity. Debug messages are disabled by default, but are useful when
troubleshooting or when developing driver support.

net.netdump.path
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.

net.netdump.polls
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.

net.netdump.retries
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.

net.netdump.arp_retries
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 dump.

HISTORY

       netdump client support first appeared in FreeBSD 12.0.

BUGS