diff --git a/sys/man/8/acpi b/sys/man/8/acpi
new file mode 100644
index 000000000..fc11c8e5c
--- /dev/null
+++ b/sys/man/8/acpi
@@ -0,0 +1,61 @@
+.TH ACPI 8
+.SH NAME
+acpi \- Advanced Configuration and Power Interface
+.SH SYNOPSIS
+.I (in plan9.ini)
+.B *acpi=
+.PP
+.B aux/acpi
+[
+.B -m
+.I mountpoint
+]
+[
+.B -s
+.I service
+]
+.SH DESCRIPTION
+.I Aux/acpi
+presents at
+.I mountpoint
+(default
+.BR /mnt/acpi )
+an interface to the ACPI. If a
+.I service
+is specified, the interface will be
+posted at
+.BI /srv/ service 
+as well.
+.PP
+The directory contains the following files.
+.TP
+.B battery
+Contains one line for each battery in the system.  Each line lists 12
+fields: the percent charge remaining, power unit used (mW or mA),
+remaining capacity, last full charge capacity, design capacity,
+warning and low capacity values,
+.BR "mV"
+separator, present voltage, design voltage, approximate time of charge
+left as
+.BR hh:mm:ss ,
+and the status (a string, one of
+.BR unknown ,
+.BR critical ,
+.BR discharging
+or
+.BR charging ).
+.TP
+.B cputemp
+Each line provides a current temperature reading of a specific CPU.
+.TP
+.B ctl
+The
+.B ctl
+file currently does not provide any functionality.
+.SH SOURCE
+.B /sys/src/cmd/aux/acpi.c
+.SH BUGS
+ACPI itself.
+.SH HISTORY
+.I Acpi
+first appeared in 9front (October, 2016).
diff --git a/sys/man/8/apm b/sys/man/8/apm
index f16f89ff4..59b0c4d30 100644
--- a/sys/man/8/apm
+++ b/sys/man/8/apm
@@ -110,3 +110,5 @@ and
 .B off
 should be supported but doing so requires
 nontrivial help from the kernel.
+.SH "SEE ALSO"
+.IR acpi (8)
diff --git a/sys/src/cmd/aux/acpi.c b/sys/src/cmd/aux/acpi.c
index 417e23275..6381ed36e 100644
--- a/sys/src/cmd/aux/acpi.c
+++ b/sys/src/cmd/aux/acpi.c
@@ -417,7 +417,7 @@ fsattach(Req *r)
 static void
 usage(void)
 {
-	fprint(2, "usage: aux/acpi [-D] [-d /dev] [-m /mnt/acpi] [-s service]\n");
+	fprint(2, "usage: aux/acpi [-Dp] [-m /mnt/acpi] [-s service]\n");
 	exits("usage");
 }
 
@@ -454,6 +454,8 @@ threadmain(int argc, char **argv)
 	case 's':
 		srv = EARGF(usage());
 		break;
+	default:
+		usage();
 	}ARGEND
 
 	if((ec = open("/dev/ec", ORDWR)) < 0)
@@ -500,7 +502,7 @@ threadmain(int argc, char **argv)
 	amlenum(amlroot, "_PSL", enumtmp, nil);
 
 	threadpostmountsrv(&fs, srv, mtpt, MREPL);
-	return;
+	threadexits(nil);
 
 fail:
 	fprint(2, "%r\n");