Written by: John H. Baldwin <jhb@FreeBSD.org>
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.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.
p The options are: l -tag -width command t Fl c Remove protection from the specified processes. t Fl d Apply the operation to all current children of the specified processes. t Fl i Apply the operation to all future children of the specified processes. t Fl g Ar pgrp Apply the operation to all processes in the specified process group. t Fl p Ar pid Apply the operation to the specified process. t Ar command Execute .Ar command as a protected process. .El
p Note that only one of the .Fl p or .Fl g flags may be specified when adjusting the state of existing processes.
p 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:
p .Dl "pgrep Xorg | xargs protect -p"
p Protect all ssh sessions and their child processes:
p .Dl "pgrep sshd | xargs protect -dip"
p Remove protection from all current and future processes:
p .Dl "protect -cdi -p 1"
p Using .Xr ps 1 to check if the protect flag has been applied to the process:
p .Dl "ps -O flags,flags2 -p 64430"
p .Dl " PID F F2 TT STAT TIME COMMAND" .Dl "64430 10104002 00000001 5 S+ 0:00.00 ./main" .Dl " ^P ^PI"
p 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 l -diag t "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.: l -dash t .Nm is not executed by root. t .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.