diff --git a/doc/sudo_logsrvd.man.in b/doc/sudo_logsrvd.man.in
index a6a4af21b..20adc9b34 100644
--- a/doc/sudo_logsrvd.man.in
+++ b/doc/sudo_logsrvd.man.in
@@ -16,7 +16,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.TH "SUDO_LOGSRVD" "@mansectsu@" "October 3, 2019" "Sudo @PACKAGE_VERSION@" "System Manager's Manual"
+.TH "SUDO_LOGSRVD" "@mansectsu@" "October 16, 2019" "Sudo @PACKAGE_VERSION@" "System Manager's Manual"
 .nh
 .if n .ad l
 .SH "NAME"
@@ -46,6 +46,16 @@ utility in the same way as logs generated directly by the
 \fBsudoers\fR
 plugin.
 .PP
+The server also supports restarting interrupted log transfers.
+To distinguish completed I/O logs from incomplete ones, the
+I/O log timing file is set to be read-only when the log is complete.
+.PP
+Configuration parameters for
+\fBsudo_logsrvd\fR
+may be specified in the
+sudo_logsrvd.conf(@mansectform@)
+file.
+.PP
 The options are as follows:
 .TP 12n
 \fB\-f\fR, \fB\--file\fR
@@ -60,7 +70,7 @@ Display a short help message to the standard output and exit.
 \fB\-n\fR, \fB\--no-fork\fR
 Run
 \fBsudo_logsrvd\fR
-in the the foreground instead of detaching from the terminal and becoming
+in the foreground instead of detaching from the terminal and becoming
 a daemon.
 .TP 12n
 \fB\-R\fR, \fB\--random-drop\fR
@@ -74,12 +84,6 @@ client to restart a connection.
 Print the
 \fBsudo_logsrvd\fR
 version and exit.
-.PP
-Configuration parameters for
-\fBsudo_logsrvd\fR
-may be set in the
-sudo_logsrvd.conf(@mansectform@)
-file.
 .SS "Debugging sudo_logsrvd"
 \fBsudo_logsrvd\fR
 supports a flexible debugging framework that is configured via
@@ -98,8 +102,12 @@ Sudo front end configuration
 .TP 26n
 \fI@sysconfdir@/sudo_logsrvd.conf\fR
 Sudo log server configuration file
+.TP 26n
+\fI@iolog_dir@\fR
+Default I/O log file location
 .SH "SEE ALSO"
 sudo.conf(@mansectform@),
+sudo_logsrvd.conf(@mansectform@),
 sudoers(@mansectform@),
 sudo(@mansectsu@),
 sudo_sendlog(@mansectsu@),
diff --git a/doc/sudo_logsrvd.mdoc.in b/doc/sudo_logsrvd.mdoc.in
index c2baa6cae..2431c75b5 100644
--- a/doc/sudo_logsrvd.mdoc.in
+++ b/doc/sudo_logsrvd.mdoc.in
@@ -15,7 +15,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd October 3, 2019
+.Dd October 16, 2019
 .Dt SUDO_LOGSRVD @mansectsu@
 .Os Sudo @PACKAGE_VERSION@
 .Sh NAME
@@ -44,6 +44,16 @@ utility in the same way as logs generated directly by the
 .Nm sudoers
 plugin.
 .Pp
+The server also supports restarting interrupted log transfers.
+To distinguish completed I/O logs from incomplete ones, the
+I/O log timing file is set to be read-only when the log is complete.
+.Pp
+Configuration parameters for
+.Nm
+may be specified in the
+.Xr sudo_logsrvd.conf @mansectform@
+file.
+.Pp
 The options are as follows:
 .Bl -tag -width Fl
 .It Fl f , -file
@@ -69,12 +79,6 @@ Print the
 .Nm
 version and exit.
 .El
-.Pp
-Configuration parameters for
-.Nm
-may be set in the
-.Xr sudo_logsrvd.conf @mansectform@
-file.
 .Ss Debugging sudo_logsrvd
 .Nm
 supports a flexible debugging framework that is configured via
@@ -92,9 +96,12 @@ please refer to its manual.
 Sudo front end configuration
 .It Pa @sysconfdir@/sudo_logsrvd.conf
 Sudo log server configuration file
+.It Pa @iolog_dir@
+Default I/O log file location
 .El
 .Sh SEE ALSO
 .Xr sudo.conf @mansectform@ ,
+.Xr sudo_logsrvd.conf @mansectform@ ,
 .Xr sudoers @mansectform@ ,
 .Xr sudo @mansectsu@ ,
 .Xr sudo_sendlog @mansectsu@ ,
diff --git a/logsrvd/iolog_writer.c b/logsrvd/iolog_writer.c
index b10717d60..296f37261 100644
--- a/logsrvd/iolog_writer.c
+++ b/logsrvd/iolog_writer.c
@@ -37,6 +37,7 @@
 #include <unistd.h>
 
 #include "log_server.pb-c.h"
+#include "sudo_gettext.h"	/* must be included before sudo_compat.h */
 #include "sudo_compat.h"
 #include "sudo_queue.h"
 #include "sudo_debug.h"
@@ -809,6 +810,7 @@ bool
 iolog_restart(RestartMessage *msg, struct connection_closure *closure)
 {
     struct timespec target;
+    struct stat sb;
     int iofd;
     debug_decl(iolog_restart, SUDO_DEBUG_UTIL)
 
@@ -830,6 +832,19 @@ iolog_restart(RestartMessage *msg, struct connection_closure *closure)
 	goto bad;
     }
 
+    /* If the timing file write bit is clear, log is already complete. */
+    if (fstatat(closure->iolog_dir_fd, "timing", &sb, 0) == -1) {
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
+	    "unable to stat %s/timing", closure->details.iolog_path);
+	goto bad;
+    }
+    if (!ISSET(sb.st_mode, S_IWUSR)) {
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
+	    "%s already complete", closure->details.iolog_path);
+	closure->errstr = _("log is already complete, cannot be restarted");
+	goto bad;
+    }
+
     /* Open existing I/O log files. */
     if (!iolog_open_all(closure->iolog_dir_fd, closure->details.iolog_path,
 	    closure->iolog_files, "r+"))
@@ -856,6 +871,8 @@ iolog_restart(RestartMessage *msg, struct connection_closure *closure)
     /* Ready to log I/O buffers. */
     debug_return_bool(true);
 bad:
+    if (closure->errstr == NULL)
+	closure->errstr = _("unable to restart log");
     debug_return_bool(false);
 }
 
diff --git a/logsrvd/logsrvd.c b/logsrvd/logsrvd.c
index 9b822428a..313ec74e8 100644
--- a/logsrvd/logsrvd.c
+++ b/logsrvd/logsrvd.c
@@ -236,7 +236,7 @@ handle_accept(AcceptMessage *msg, struct connection_closure *closure)
 	debug_return_bool(true);
     }
 
-    /* Send log ID to client for restarting connectoins. */
+    /* Send log ID to client for restarting connections. */
     if (!fmt_log_id_message(closure->details.iolog_path, &closure->write_buf))
 	debug_return_bool(false);
     if (sudo_ev_add(NULL, closure->write_ev, NULL, false) == -1) {
@@ -297,6 +297,7 @@ static bool
 handle_exit(ExitMessage *msg, struct connection_closure *closure)
 {
     struct timespec tv = { 0, 0 };
+    mode_t mode;
     debug_decl(handle_exit, SUDO_DEBUG_UTIL)
 
     if (closure->state != RUNNING) {
@@ -325,6 +326,14 @@ handle_exit(ExitMessage *msg, struct connection_closure *closure)
 	__func__, (long long)closure->elapsed_time.tv_sec,
 	closure->elapsed_time.tv_nsec);
 
+    /* Clear write bits from I/O timing file to indicate completion. */
+    mode = logsrvd_conf_iolog_mode();
+    CLR(mode, S_IWUSR|S_IWGRP|S_IWOTH);
+    if (fchmodat(closure->iolog_dir_fd, "timing", mode, 0) == -1) {
+	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
+	    "unable to fchmodat timing file");
+    }
+
     /* Schedule the final commit point event immediately. */
     if (sudo_ev_add(NULL, closure->commit_ev, &tv, false) == -1) {
 	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
@@ -352,7 +361,7 @@ handle_restart(RestartMessage *msg, struct connection_closure *closure)
     if (!iolog_restart(msg, closure)) {
 	sudo_debug_printf(SUDO_DEBUG_WARN, "%s: unable to restart I/O log", __func__);
 	/* XXX - structured error message so client can send from beginning */
-	if (!fmt_error_message("unable to restart log", &closure->write_buf))
+	if (!fmt_error_message(closure->errstr, &closure->write_buf))
 	    debug_return_bool(false);
 	sudo_ev_del(NULL, closure->read_ev);
 	if (sudo_ev_add(NULL, closure->write_ev, NULL, false) == -1) {
diff --git a/logsrvd/logsrvd.h b/logsrvd/logsrvd.h
index 652976ad5..1f59ee3fb 100644
--- a/logsrvd/logsrvd.h
+++ b/logsrvd/logsrvd.h
@@ -145,6 +145,7 @@ int logsrvd_conf_syslog_facility(void);
 int logsrvd_conf_syslog_acceptpri(void);
 int logsrvd_conf_syslog_rejectpri(void);
 int logsrvd_conf_syslog_alertpri(void);
+mode_t logsrvd_conf_iolog_mode(void);
 const char *logsrvd_conf_logfile_path(void);
 const char *logsrvd_conf_logfile_time_format(void);
 
diff --git a/logsrvd/logsrvd_conf.c b/logsrvd/logsrvd_conf.c
index 467d34207..dd603bacb 100644
--- a/logsrvd/logsrvd_conf.c
+++ b/logsrvd/logsrvd_conf.c
@@ -98,6 +98,12 @@ static struct logsrvd_config {
 } *logsrvd_config;
 
 /* iolog getters */
+mode_t
+logsrvd_conf_iolog_mode(void)
+{
+    return logsrvd_config->iolog.mode;
+}
+
 const char *
 logsrvd_conf_iolog_dir(void)
 {