Viewing: dump_on_eviction.4
.TH DUMP_ON_EVICTION 4 2026-03-31 "Lustre" "Lustre Kernel Parameters"
.SH NAME
dump_on_eviction, lbug_on_eviction \- configure subsystem log and crash events
.SH SYNOPSIS
.SY
.B lctl set_param dump_on_eviction=
.RI { SUBSYSTEM_LIST | HEX_MASK }
.SY
.B lctl set_param lbug_on_eviction=
.RI { SUBSYSTEM_LIST | HEX_MASK }
.SY
.B lctl get_param dump_on_eviction
.SY
.B lctl get_param lbug_on_eviction
.YS
.SS PROPERTIES
.TP
.RB Access Permissions
.br
.BR 644 " | " -rw--r--r--
.TP
.B Scope
.br
Global
.TP
.B Config
.br
Always present
.B
.TP
.B Default
.br
.RB dump_on_eviction= 0
.br
.RB lbug_on_eviction= 0
.SH DESCRIPTION
The
.B dump_on_eviction
and
.B lbug_on_eviction
parameters control the behavior of the Lustre filesystem when client
eviction events occur.
Eviction refers to the forced removal of a client, lock, or recovery
context from the system due to timeout or other failure conditions.
.PP
These parameters allow fine-grained control over whether Lustre dumps
a debugging log file with detailed diagnostic information
.RB ( dump_on_eviction )
or triggers an immediate kernel crash
.RB ( lbug_on_eviction )
upon eviction events in specific subsystems.
.PP
The
.I SUBSYSTEM_LIST
parameter can be either a comma, space, or plus-separated list of
subsystem names, or a
.I HEX_MASK
(hexadecimal or decimal number).
.PP
The value of output setting uses space-separated list.
.EX
.RB client# "lctl get_param dump_on_eviction"
dump_on_eviction=ldlm stale
.EE
.PP
The following subsystems are supported:
.TP
.BR 1 " (0x01)"
Special alias for enabling all subsystems except pinger, this is old behavior:
.BR llite ", " ldlm ", " stale ". Equivalent to mask " 0x0E .
.TP
.BR llite "(0x02)"
Client eviction during reconnect, the server informs the client that it has
been evicted. This affects the client-side, but server could be a client to
another server.
.TP
.BR ldlm " (0x04)"
Eviction by LDLM (Distributed Lock Manager) due to lock callback timer expired,
server side event.
.TP
.BR stale " (0x08)"
Eviction triggered by stale recovery state — e.g., when a client fails to
reconnect within recovery timeout and its state is considered abandoned by
the MDS/OSS, server side.
.TP
.BR pinger " (0x10)"
Eviction of a client due to failure at pinger heartbeats —
the server did not receive a request from the client during the waiting time.
Previously, pinger evictions did not trigger logging or crashes;
this subsystem enables diagnostic behavior.
.PP
The
.B lbug_on_eviction
parameter will trigger an immediate kernel crash (
.BR LBUG() )
when any matching eviction event occurs.
Typically this is only used to capture a crashdump of the full kernel
memory in order to perform in-depth debugging activity.
.PP
The parameter
.B dump_on_eviction
behaves similarly but only dumps the Lustre debug log without crashing
the system. This is useful for debugging production systems where crashes
are undesirable.
.SH EXAMPLES
.B Use lbug_on_eviction carefully, as it will crash a server on errors.
Pinger and ldlm evictions often occur due to network problems.
.PP
Enable logging for LDLM and stale recovery evictions (no crash):
.EX
.RB oss3# " lctl set_param dump_on_eviction=ldlm+stale"
.EE
.PP
Trigger kernel crash on client eviction:
.EX
.RB client# " lctl set_param lbug_on_eviction=llite"
.EE
.PP
Enable logging and crashes for all eviction types:
.EX
.RB mds1# " lctl set_param dump_on_eviction=ldlm,stale,pinger"
.RB oss3# " lctl set_param lbug_on_eviction=0x1E"
.EE
.PP
Disable all eviction logging (default behavior):
.EX
.RB # " lctl set_param dump_on_eviction=0"
.RB # " lctl set_param lbug_on_eviction=0"
.EE
.SH AVAILABILITY
The
.B dump_on_eviction
and
.B lbug_on_eviction
parameters are part of the
.BR lustre (7)
filesystem since release 2.12.0,
.\" Added in commit v2_11_55_0-22-g97381ffc92
but the ability to specify
.I SUBSYSTEM_LIST
or
.I HEX_MASK
is only available since release 2.18.0.
.\" Added in commit v2_17_50-86-g4e402a4bca
.SH SEE ALSO
.BR lctl-get_param (8),
.BR lctl-set_param (8)
