xref: /freebsd/usr.bin/protect/protect.1 (revision 6452fb1e87ed9d00b52fa1e63e7c3a7516c9586c)

.\" Copyright (c) 2013 Hudson River Trading LLC
.\" Written by: John H. Baldwin <jhb@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd July 12, 2022
.Dt PROTECT 1
.Os
.Sh NAME
.Nm protect
.Nd "protect processes from being killed when swap space is exhausted"
.Sh SYNOPSIS
.Nm
.Op Fl i
.Ar command
.Nm
.Op Fl cdi
.Fl g Ar pgrp
.Nm
.Op Fl cdi
.Fl p Ar pid
.Sh DESCRIPTION
The
.Nm
command is used to mark processes as protected.
The kernel does not kill protected processes when swap space is exhausted.
Note that this protected state is not inherited by child processes by default.
.Pp
The options are:
.Bl -tag -width command
.It Fl c
Remove protection from the specified processes.
.It Fl d
Apply the operation to all current children of the specified processes.
.It Fl i
Apply the operation to all future children of the specified processes.
.It Fl g Ar pgrp
Apply the operation to all processes in the specified process group.
.It Fl p Ar pid
Apply the operation to the specified process.
.It Ar command
Execute
.Ar command
as a protected process.
.El
.Pp
Note that only one of the
.Fl p
or
.Fl g
flags may be specified when adjusting the state of existing processes.
.Pp
Daemons can be protected on startup using
.Ao Ar name Ac Ns Va _oomprotect
option from
.Xr rc.conf 5 .
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
Mark the Xorg server as protected:
.Pp
.Dl "pgrep Xorg | xargs protect -p"
.Pp
Protect all ssh sessions and their child processes:
.Pp
.Dl "pgrep sshd | xargs protect -dip"
.Pp
Remove protection from all current and future processes:
.Pp
.Dl "protect -cdi -p 1"
.Pp
Using
.Xr ps 1
to check if the protect flag has been applied to the process:
.Pp
.Dl "ps -O flags,flags2 -p 64430"
.Pp
.Dl " PID        F       F2 TT  STAT    TIME COMMAND"
.Dl "64430 10104002 00000001  5  S+   0:00.00 ./main"
.Dl "        ^P            ^PI"
.Pp
In the above example
.Nm P
points at the protected flag and
.Nm PI
points at the inheritance flag.
The process is protected if
.Nm P
bit is set to 1.
All children of this process will also be protected if
.Nm PI
bit is set to 1.
.Sh DIAGNOSTICS
.Bl -diag
.It "protect: procctl: Operation not permitted"
The
.Nm
command does not have the required permissions to protect selected processes.
There are many reasons why this could be the case, e.g.:
.Bl -dash
.It
.Nm
is not executed by root.
.It
.Nm
is executed inside a
.Xr jail 8 ,
which is not supported at the moment.
.El
.El
.Sh SEE ALSO
.Xr ps 1 ,
.Xr procctl 2 ,
.Xr rc.conf 5
.Sh BUGS
If you protect a runaway process that allocates all memory the system will
deadlock.