diff --git a/xCAT-server/lib/perl/xCAT/SvrUtils.pm b/xCAT-server/lib/perl/xCAT/SvrUtils.pm
index b15aa3002..a4440e7b3 100644
--- a/xCAT-server/lib/perl/xCAT/SvrUtils.pm
+++ b/xCAT-server/lib/perl/xCAT/SvrUtils.pm
@@ -1693,6 +1693,45 @@ sub nfs_export_exists {
     return 0;
 }
 
+#-----------------------------------------------------------------------------
+
+=head3 nfs_export_line
+
+    The /etc/exports line for a directory a service node serves to its nodes.
+
+    Arguments:
+        $dir        the directory to export
+        reexport    true when $dir is itself an NFS mount
+
+    Returns:
+        one export line, with no trailing newline.
+
+    A local directory keeps the options xCAT has always written. Re-exporting an NFS mount needs
+    two more: the kernel cannot derive a filesystem id for one, so exportfs refuses it without an
+    explicit fsid, and crossmnt lets a client cross into the mount below. The fsid is derived
+    from the path so that it survives a restart -- a new one would make every client's mount
+    stale.
+
+=cut
+
+#-----------------------------------------------------------------------------
+sub nfs_export_line {
+    my ( $dir, %opts ) = _nfs_method_args(@_);
+    my $options = 'rw,no_root_squash,sync,no_subtree_check,insecure';
+    if ( $opts{reexport} ) {
+        $options .= ',crossmnt,fsid=' . _nfs_export_fsid($dir);
+    }
+    return "$dir *($options)";
+}
+
+# A stable, non-zero fsid for a path. 0 is reserved for the export root.
+sub _nfs_export_fsid {
+    my ($dir) = @_;
+    my $sum = 0;
+    $sum = ( $sum * 31 + ord($_) ) % 2147483647 for split //, $dir;
+    return $sum || 1;
+}
+
 sub _ensure_nfs_exported {
     my ($nfsserver, $nfsdirectory, $callback, %opts) = @_;
     my $export_options = 'rw,no_root_squash,sync,no_subtree_check,insecure';
diff --git a/xCAT-server/lib/xcat/plugins/AAsn.pm b/xCAT-server/lib/xcat/plugins/AAsn.pm
index 188d7ebdc..bc5350ccf 100644
--- a/xCAT-server/lib/xcat/plugins/AAsn.pm
+++ b/xCAT-server/lib/xcat/plugins/AAsn.pm
@@ -919,6 +919,24 @@ sub setup_NFS
     my $rc = 0;
     if (xCAT::Utils->isLinux())
     {
+        # servicenode.nfsserver=1 means this node serves files to the nodes behind it. With
+        # site.installloc set it MOUNTS the install directory from the management node and the
+        # caller exports nothing, so the node served no NFS at all: an Ubuntu compute node stops
+        # at "Unable to find a live file system on the network", because casper mounts the
+        # install tree over NFS from its own service node. Exporting a mount needs an fsid, which
+        # nfs_export_line adds.
+        my $installdir = xCAT::TableUtils->getInstallDir() || "/install";
+        unless (xCAT::SvrUtils->nfs_export_exists($installdir))
+        {
+            my $line = xCAT::SvrUtils->nfs_export_line($installdir,
+                reexport => (xCAT::Utils->isMounted($installdir) ? 1 : 0));
+            xCAT::Utils->runcmd("/bin/echo '$line' >> /etc/exports", 0);
+            if ($::RUNCMD_RC != 0)
+            {
+                xCAT::MsgUtils->message('S', "Could not add $installdir to /etc/exports.");
+            }
+        }
+
         #my $os = xCAT::Utils->osver();
         #if ($os =~ /sles.*/)
         #{
@@ -930,6 +948,14 @@ sub setup_NFS
         #    $rc = xCAT::Utils->startService("nfs");
         #}
         $rc = xCAT::Utils->startservice("nfs");
+
+        # After the daemon, so a fresh export is picked up. An export the kernel refuses is
+        # reported and does not fail the service node, which has other services to set up.
+        xCAT::Utils->runcmd("/usr/sbin/exportfs -a", 0);
+        if ($::RUNCMD_RC != 0)
+        {
+            xCAT::MsgUtils->message('S', "Error with /usr/sbin/exportfs -a.");
+        }
     }
     else
     {    #AIX
diff --git a/xCAT-test/unit/svrutils_nfs_export_line.t b/xCAT-test/unit/svrutils_nfs_export_line.t
new file mode 100644
index 000000000..3adbfcbfc
--- /dev/null
+++ b/xCAT-test/unit/svrutils_nfs_export_line.t
@@ -0,0 +1,52 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use FindBin;
+use Test::More;
+
+# A service node with servicenode.nfsserver=1 is asked to "set up file services on this service
+# node". When site.installloc is set it MOUNTS /install from the management node, and AAsn.pm
+# then exported nothing at all, so the node served no NFS. An Ubuntu compute node boots the live
+# installer with casper, which mounts the install tree over NFS from its own service node, and it
+# stopped at "Unable to find a live file system on the network". Measured on xcat22-sn:
+# showmount -e returned an empty list and /etc/exports was empty while nfs-kernel-server was
+# active.
+#
+# Re-exporting an NFS mount is not the same as exporting a local directory. Linux requires an
+# explicit fsid, because it cannot derive one from the underlying filesystem, and refuses the
+# export without it.
+
+use lib "$FindBin::Bin/../../perl-xCAT";
+use lib "$FindBin::Bin/../../xCAT-server/lib/perl";
+use xCAT::SvrUtils;
+
+can_ok('xCAT::SvrUtils', 'nfs_export_line') or done_testing() && exit;
+
+my $local = xCAT::SvrUtils->nfs_export_line('/install');
+is($local, '/install *(rw,no_root_squash,sync,no_subtree_check,insecure)',
+    'a local directory keeps the options xCAT has always written');
+
+my $reexport = xCAT::SvrUtils->nfs_export_line('/install', reexport => 1);
+like($reexport, qr{^/install \*\(},            're-export names the same directory and clients');
+like($reexport, qr{\brw\b},                    '... stays read-write');
+like($reexport, qr{\bno_root_squash\b},        '... keeps no_root_squash, which the installer needs');
+like($reexport, qr{\binsecure\b},              '... keeps insecure, for clients on high ports');
+like($reexport, qr{\bfsid=\d+},                '... carries an fsid, without which exportfs refuses an NFS mount');
+like($reexport, qr{\bcrossmnt\b},              '... carries crossmnt, so the mount below it is followed');
+
+# The fsid must be stable across runs, or every restart hands clients a new filesystem identity
+# and their mounts go stale.
+is(xCAT::SvrUtils->nfs_export_line('/install', reexport => 1), $reexport,
+    'the same directory yields the same fsid every time');
+
+my ($install_fsid) = $reexport      =~ /fsid=(\d+)/;
+my ($tftp_fsid)    = xCAT::SvrUtils->nfs_export_line('/tftpboot', reexport => 1) =~ /fsid=(\d+)/;
+isnt($tftp_fsid, $install_fsid, 'two directories do not share one fsid');
+cmp_ok($install_fsid, '>', 0, 'the fsid is not 0, which Linux reserves for the export root');
+# The guard that keeps it non-zero is only reachable when the checksum itself is 0, which an
+# empty path produces. Drive it directly rather than claim a path that cannot reach it.
+cmp_ok(xCAT::SvrUtils::_nfs_export_fsid(''), '>', 0,
+    'a path whose checksum is 0 still yields a usable fsid');
+
+done_testing();