root dir for execdriver (/var/run/docker) should be configurable

Signed-off-by: Shishir Mahajan <shishir.mahajan@redhat.com>

contrib/completion/bash/docker

@@ -1161,6 +1161,7 @@ _docker() {
 		--dns-search
 		--exec-driver -e
 		--exec-opt
+		--exec-root
 		--fixed-cidr
 		--fixed-cidr-v6
 		--graph -g

daemon/config.go

@@ -25,6 +25,7 @@ type CommonConfig struct {
 	DnsSearch      []string
 	EnableCors     bool
 	ExecDriver     string
+	ExecRoot       string
 	GraphDriver    string
 	Labels         []string
 	LogConfig      runconfig.LogConfig
@@ -38,9 +39,11 @@ type CommonConfig struct {
 // the current process.
 // Subsequent calls to `flag.Parse` will populate config with values parsed
 // from the command-line.
+
 func (config *Config) InstallCommonFlags() {
 	flag.StringVar(&config.Pidfile, []string{"p", "-pidfile"}, defaultPidFile, "Path to use for daemon PID file")
 	flag.StringVar(&config.Root, []string{"g", "-graph"}, defaultGraph, "Root of the Docker runtime")
+	flag.StringVar(&config.ExecRoot, []string{"-exec-root"}, "/var/run/docker", "Root of the Docker execdriver")
 	flag.BoolVar(&config.AutoRestart, []string{"#r", "#-restart"}, true, "--restart on the daemon has been deprecated in favor of --restart policies on docker run")
 	flag.BoolVar(&config.Bridge.EnableIptables, []string{"#iptables", "-iptables"}, true, "Enable addition of iptables rules")
 	flag.BoolVar(&config.Bridge.EnableIpForward, []string{"#ip-forward", "-ip-forward"}, true, "Enable net.ipv4.ip_forward")

daemon/daemon.go

@@ -911,8 +911,7 @@ func NewDaemon(config *Config, registryService *registry.Service) (daemon *Daemo
 	}
 
 	sysInfo := sysinfo.New(false)
-	const runDir = "/var/run/docker"
-	ed, err := execdrivers.NewDriver(config.ExecDriver, config.ExecOptions, runDir, config.Root, sysInitPath, sysInfo)
+	ed, err := execdrivers.NewDriver(config.ExecDriver, config.ExecOptions, config.ExecRoot, config.Root, sysInitPath, sysInfo)
 	if err != nil {
 		return nil, err
 	}

docs/man/docker.1.md

@@ -56,6 +56,9 @@ To see the man page for a command run **man docker <command>**.
 **--exec-opt**=[]
   Set exec driver options. See EXEC DRIVER OPTIONS.
 
+**--exec-root**=""
+  Path to use as the root of the Docker execdriver. Default is `/var/run/docker`.
+
 **--fixed-cidr**=""
   IPv4 subnet for fixed IPs (e.g., 10.20.0.0/16); this subnet must be nested in the bridge subnet (which is defined by \-b or \-\-bip)
 

docs/sources/reference/commandline/cli.md

@@ -152,6 +152,7 @@ expect an integer, and they can only be specified once.
       --default-ulimit=[]                    Set default ulimit settings for containers
       -e, --exec-driver="native"             Exec driver to use
       --exec-opt=[]                          Set exec driver options
+      --exec-root="/var/run/docker"          Root of the Docker execdriver
       --fixed-cidr=""                        IPv4 subnet for fixed IPs
       --fixed-cidr-v6=""                     IPv6 subnet for fixed IPs
       -G, --group="docker"                   Group for the unix socket