diff --git a/osbase/logtree/logtree.go b/osbase/logtree/logtree.go
new file mode 100644
index 0000000..c20681d
--- /dev/null
+++ b/osbase/logtree/logtree.go
@@ -0,0 +1,158 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package logtree
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+
+	"source.monogon.dev/osbase/logbuffer"
+)
+
+// LogTree is a tree-shaped logging system. For more information, see the package-
+// level documentation.
+type LogTree struct {
+	// journal is the tree's journal, storing all log data and managing subscribers.
+	journal *journal
+	// root is the root node of the actual tree of the log tree. The nodes contain per-
+	// DN configuration options, notably the current verbosity level of that DN.
+	root *node
+}
+
+func New() *LogTree {
+	lt := &LogTree{
+		journal: newJournal(),
+	}
+	lt.root = newNode(lt, "")
+	return lt
+}
+
+// node represents a given DN as a discrete 'logger'. It implements the
+// LeveledLogger interface for log publishing, entries from which it passes over to
+// the logtree's journal.
+type node struct {
+	// dn is the DN which this node represents (or "" if this is the root node).
+	dn DN
+	// tree is the LogTree to which this node belongs.
+	tree *LogTree
+	// verbosity is the current verbosity level of this DN/node, affecting .V(n)
+	// LeveledLogger calls
+	verbosity     VerbosityLevel
+	rawLineBuffer *logbuffer.LineBuffer
+
+	// mu guards children.
+	mu sync.Mutex
+	// children is a map of DN-part to a children node in the logtree. A DN-part is a
+	// string representing a part of the DN between the deliming dots, as returned by
+	// DN.Path.
+	children map[string]*node
+}
+
+// newNode returns a node at a given DN in the LogTree - but doesn't set up the
+// LogTree to insert it accordingly.
+func newNode(tree *LogTree, dn DN) *node {
+	n := &node{
+		dn:       dn,
+		tree:     tree,
+		children: make(map[string]*node),
+	}
+	// TODO(q3k): make this limit configurable. If this happens, or the default (1024) gets changes, max chunk size
+	// calculations when serving the logs (eg. in NodeDebugService) must reflect this.
+	n.rawLineBuffer = logbuffer.NewLineBuffer(1024, n.logRaw)
+	return n
+}
+
+// nodeByDN returns the LogTree node corresponding to a given DN. If either the
+// node or some of its parents do not exist they will be created as needed.
+func (l *LogTree) nodeByDN(dn DN) (*node, error) {
+	traversal, err := newTraversal(dn)
+	if err != nil {
+		return nil, fmt.Errorf("traversal failed: %w", err)
+	}
+	return traversal.execute(l.root), nil
+}
+
+// nodeTraversal represents a request to traverse the LogTree in search of a given
+// node by DN.
+type nodeTraversal struct {
+	// want is the DN of the node's that requested to be found.
+	want DN
+	// current is the path already taken to find the node, in the form of DN parts. It
+	// starts out as want.Parts() and progresses to become empty as the traversal
+	// continues.
+	current []string
+	// left is the path that's still needed to be taken in order to find the node, in
+	// the form of DN parts. It starts out empty and progresses to become wants.Parts()
+	// as the traversal continues.
+	left []string
+}
+
+// next adjusts the traversal's current/left slices to the next element of the
+// traversal, returns the part that's now being looked for (or "" if the traveral
+// is done) and the full DN of the element that's being looked for.
+//
+// For example, a traversal of foo.bar.baz will cause .next() to return the
+// following on each invocation:
+//   - part: foo, full: foo
+//   - part: bar, full: foo.bar
+//   - part: baz, full: foo.bar.baz
+//   - part: "",  full: foo.bar.baz
+func (t *nodeTraversal) next() (part string, full DN) {
+	if len(t.left) == 0 {
+		return "", t.want
+	}
+	part = t.left[0]
+	t.current = append(t.current, part)
+	t.left = t.left[1:]
+	full = DN(strings.Join(t.current, "."))
+	return
+}
+
+// newTraversal returns a nodeTraversal fora a given wanted DN.
+func newTraversal(dn DN) (*nodeTraversal, error) {
+	parts, err := dn.Path()
+	if err != nil {
+		return nil, err
+	}
+	return &nodeTraversal{
+		want: dn,
+		left: parts,
+	}, nil
+}
+
+// execute the traversal in order to find the node. This can only be called once
+// per traversal. Nodes will be created within the tree until the target node is
+// reached. Existing nodes will be reused. This is effectively an idempotent way of
+// accessing a node in the tree based on a traversal.
+func (t *nodeTraversal) execute(n *node) *node {
+	cur := n
+	for {
+		part, full := t.next()
+		if part == "" {
+			return cur
+		}
+
+		mu := &cur.mu
+		mu.Lock()
+		if _, ok := cur.children[part]; !ok {
+			cur.children[part] = newNode(n.tree, full)
+		}
+		cur = cur.children[part]
+		mu.Unlock()
+	}
+}