diff --git a/helper/tmpdir-setup b/helper/tmpdir-setup
index 01207427..aab193f4 100755
--- a/helper/tmpdir-setup
+++ b/helper/tmpdir-setup
@@ -1,42 +1,60 @@
 #! /usr/bin/bash
 
-# Input (environment):
-#
-#   MXQ_JOBID   : job ident
-#   MXQ_SIZE    : size in GB
-#   MXQ_UID     : uid
-
-# Output:
-#
-#   /dev/shm/mxqd/tmp/$JOBID  mounted, space from /scratch/local2
+usage() {
+    cat <<EOF >&2
+usage:
+    $0 create JOBID SIZE UID  # create SIZE GiB /dev/shm/mxqd/mnt/job/$JOBID
+EOF
+    exit 1
+}
 
 tmpdir=/scratch/local2/mxqd/tmp
 mntdir=/dev/shm/mxqd/mnt/job
-filename=$tmpdir/$MXQ_JOBID.tmp
-mountpoint=$mntdir/$MXQ_JOBID
-
-umask 006
-mkdir -p $tmpdir
-mkdir -p $mntdir
-
-status=1;
-
-if fallocate -l ${MXQ_SIZE}G $filename; then
-    if loopdevice=$(losetup --find --show $filename); then
-        if mkfs.ext4 \
-                -q \
-                -m 0 \
-                -E nodiscard,mmp_update_interval=300,lazy_journal_init=1,root_owner=$MXQ_UID:0 \
-                -O '64bit,ext_attr,filetype,^has_journal,huge_file,inline_data,^mmp,^quota,sparse_super2' \
-                $loopdevice \
-                && mkdir -p $mountpoint && mount -Odata=writeback,barrier=0  $loopdevice $mountpoint; then
-            rmdir $mountpoint/lost+found
-            status=0
+
+cmd_create() {
+    (( $# == 3 )) || usage
+    MXQ_JOBID=$1
+    MXQ_SIZE=$2
+    MXQ_UID=$3
+
+    filename=$tmpdir/$MXQ_JOBID.tmp
+    mountpoint=$mntdir/$MXQ_JOBID
+
+    umask 006
+    mkdir -p $tmpdir
+    mkdir -p $mntdir
+
+    status=1;
+
+    if fallocate -l ${MXQ_SIZE}G $filename; then
+        if loopdevice=$(losetup --find --show $filename); then
+            if mkfs.ext4 \
+                    -q \
+                    -m 0 \
+                    -E nodiscard,mmp_update_interval=300,lazy_journal_init=1,root_owner=$MXQ_UID:0 \
+                    -O '64bit,ext_attr,filetype,^has_journal,huge_file,inline_data,^mmp,^quota,sparse_super2' \
+                    $loopdevice \
+                    && mkdir -p $mountpoint && mount -Odata=writeback,barrier=0  $loopdevice $mountpoint; then
+                rmdir $mountpoint/lost+found
+                status=0
+            fi
+            losetup -d $loopdevice
         fi
-        losetup -d $loopdevice
+        rm $filename
+    else
+        test -e $filename && rm $filename
     fi
-    rm $filename
-else
-    test -e $filename && rm $filename
-fi
-exit $status
+    exit $status
+}
+
+(( $# > 0 )) || usage
+cmd="$1"
+shift;
+case "$cmd" in
+    create)
+        cmd_create "$@"
+        ;;
+    *)
+        usage
+        ;;
+esac
diff --git a/mxqd.c b/mxqd.c
index 098595cf..6bb06af0 100644
--- a/mxqd.c
+++ b/mxqd.c
@@ -1292,7 +1292,6 @@ static unsigned long start_job(struct mxq_group_list *glist)
 
     pid_t pid;
     int res;
-    int status;
 
     assert(glist);
     assert(glist->user);
@@ -1310,28 +1309,21 @@ static unsigned long start_job(struct mxq_group_list *glist)
 
     if (group->job_tmpdir_size > 0) {
         mx_mysql_disconnect(server->mysql);
-        pid = fork();
-        if (pid==0) {
-            char *argv[2];
-            char *envp[4];
-            argv[0] = tmpdir_script,
-            argv[1] = NULL;
-            envp[0] = mx_asprintf_forever("MXQ_JOBID=%lu", job->job_id);
-            envp[1] = mx_asprintf_forever("MXQ_SIZE=%u", group->job_tmpdir_size);
-            envp[2] = mx_asprintf_forever("MXQ_UID=%d", group->user_uid);
-            envp[3] = NULL;
-            execve(tmpdir_script, argv,envp);
-            mx_log_fatal("exec %s : %m", tmpdir_script);
-            exit(1);
-        }
+        char *argv[] = {
+            tmpdir_script,
+            "create",
+            mx_asprintf_forever("%lu", job->job_id),
+            mx_asprintf_forever("%u", group->job_tmpdir_size),
+            mx_asprintf_forever("%d", group->user_uid),
+            NULL
+        };
+        int status = mx_call_external(tmpdir_script, argv);
+        free(argv[2]);
+        free(argv[3]);
+        free(argv[4]);
         mx_mysql_connect_forever(&(server->mysql));
-        if (pid < 0) {
-            mx_log_err("fork: %m");
-            mxq_unload_job_from_server(server->mysql, job->job_id);
-            return(0);
-        }
-        waitpid(pid, &status, 0);
-        if (status) {
+        if (status == -1) {
+            mx_log_err("create job tmpdir: %m");
             mxq_unload_job_from_server(server->mysql, job->job_id);
             return 0;
         }