Month: October 2018

Network problems in Docker can often be “fixed” by deleting /var/lib/docker/network/files/local-kv.db. However, in some cases it might be possible to just edit the bits that are wrong. This file is a BoltDB database.

Here’s some code to extract the keys contained in the file (libkv_example.go, heavily inspired by the example code in libkv/docs/examples.md)

package main

import (
    "time"
    "log"

    "github.com/docker/libkv"
    "github.com/docker/libkv/store"
    "github.com/docker/libkv/store/boltdb"
)

func init() {
    // Register boltdb store to libkv
    boltdb.Register()
}

func main() {
    client := "./local-kv.db" // ./ appears to be necessary

    // Initialize a new store
    kv, err := libkv.NewStore(
        store.BOLTDB, // or "boltdb"
        []string{client},
        &store.Config{
            Bucket: "libnetwork",
            ConnectionTimeout: 10*time.Second,
        },
    )
    if err != nil {
        log.Fatalf("Cannot create store: %v", err)
    }

    pair, err := kv.List("docker/network")
    for _, p := range pair {
        println("key:", string(p.Key))
        println("value:", string(p.Value))
    }
}

Make sure to work on a copy of your local-kv.db file, and that you have write permissions to your copy. Also note that this script is anything but thoroughly tested.

If you’re new to go like me, here are the commands to install Go, the required libraries and run the program (if you’re on Debian):

sudo apt-get install golang-1.8-go
PATH=/usr/lib/go-1.8/bin/:$PATH
# feel free to try go build libkv_example.go without the go get commands
# you'll most likely get an error like this:
# libkv_example.go:7:5: cannot find package "github.com/docker/libkv" in any of:
# ...
go get github.com/docker/libkv
go get go.etcd.io/bbolt
go build libkv_example.go
./libkv_example