linux – 如何在docker中成功启用udev同步？

我已经从这个site下载并安装了静态链接的docker 1.6.1,并在RHEL 7.1上运行它：

[root@localhost bin]# ./docker -d
WARN[0000] Udev sync is not supported. This will lead to unexpected behavior,data loss and errors
INFO[0000] +job init_networkdriver()
INFO[0000] +job serveapi(unix:///var/run/docker.sock)
INFO[0000] Listening for HTTP on unix (/var/run/docker.sock)
INFO[0000] -job init_networkdriver() = OK (0)
INFO[0000] Loading containers: start.

INFO[0000] Loading containers: done.
INFO[0000] docker daemon: 1.6.1 97cd073; execdriver: native-0.2; graphdriver: devicemapper
INFO[0000] +job acceptconnections()
INFO[0000] -job acceptconnections() = OK (0)
INFO[0000] Daemon has completed initialization

我可以看到有一个警告：“不支持Udev同步.这将导致意外行为,数据丢失和错误”,并且在检查docker源代码后,我发现警告日志来自deviceset.go：

func (devices *DeviceSet) initDevmapper(doInit bool) error {
    ......

    // https://github.com/docker/docker/issues/4036
    if supported := devicemapper.UdevSetSyncSupport(true); !supported {
        log.Warnf("Udev sync is not supported. This will lead to unexpected behavior,data loss and errors")
    }
    log.Debugf("devicemapper: udev sync support: %v",devicemapper.UdevSyncSupported())

    ......
}

devicemapper.UdevSetSyncSupport是这样的：

// UdevSyncSupported returns whether device-mapper is able to sync with udev
//
// This is essential otherwise race conditions can arise where both udev and
// device-mapper attempt to create and destroy devices.
func UdevSyncSupported() bool {
    return DmUdevGetSyncSupport() != 0
}

// UdevSetSyncSupport allows setting whether the udev sync should be enabled.
// The return bool indicates the state of whether the sync is enabled.
func UdevSetSyncSupport(enable bool) bool {
    if enable {
        DmUdevSetSyncSupport(1)
    } else {
        DmUdevSetSyncSupport(0)
    }
    return UdevSyncSupported()
}

我可以看到原因是启用udev同步失败.如何成功启用udev同步？

更新：
检查dm_udev_set_sync_support的反汇编代码后：

(gdb) disassemble dm_udev_set_sync_support
Dump of assembler code for function dm_udev_set_sync_support:
=> 0x0000000000a3e4e0 <+0>:     repz retq
End of assembler dump.

它是一个空函数,什么都不做,没有提到set sync支持.这是否意味着这个静态构建的docker二进制文件是不可用的？

最佳答案

我不能重现你的问题;我得到以下内容：

(gdb) disassemble dm_udev_set_sync_support
Dump of assembler code for function dm_udev_set_sync_support@plt:
   0x0000000000403420 <+0>:     jmpq   *0xda8c92(%rip)        # 0x11ac0b8 

帮自己一个忙：忽略docker.io所做的构建,直接从RHEL获取Docker.它可以在Extras频道中找到.虽然它通常比上游版本落后几周(例如1.6而不是1.7),但它也经过了充分测试并保证实际工作.