jlink 错误 ：Can not connect to J-Link via USB

//环境：centos6，jlink连接44b0开发板

$ ./JLinkExe

Can not connect to J-Link via USB.

有贴：检查USB连接，USB驱动，ARM7复位脚连接复位芯片和J-LINK复位脚相重。去掉复位芯片。
相应J-LINK设置正确，运行J-LINKARM.EXE。  （偶刚入门，尚不知哪是复位脚，so另找出路）
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一贴：切换到xp，连接jlink，打开成功后再切回linux就解决问题。 (我就不幸运了,继续寻找)
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一贴：//http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka15933.html
原文解释：
“The J-Link device is probably configured for a J-Link USB ID other than 0. Due to that, it can't be recognized by the uVision J-Link Debugger driver used for ARM7/9 devices.
RESOLUTION

Configure the J-Link for USB ID 0. This can be done with the J-Link commander tool found in the MDK-ARM installation directory C:\Keil\ARM\Segger\JLink.exe. This will identify the J-Link with ID different than 0 and when connected, provides a command "usbaddr" to change the ID:”

J-Link>USBADDR=0
USB地址成功变更为'0'。请拔下设备，然后再插回去。
J-LINK>
后重新连接到PC上。
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J-Link>USBADDR=0
但我这还是提示：No communication with J-Link !
而且修改speed时
J-Link>speed 50000
JTAG speed: 0 kHz
比较晕。 怀疑是驱动问题，在官网又找了个V4.69b的驱动.(http://www.segger.com/jlink-software.html?step=&file=JLinkLinux_469b&serial=)
先安装好libusb,libreadline,再安装jlink v4.69b.可以了。提示：
SEGGER J-Link Commander V4.69b ('?' for help)
Compiled Apr 19 2013 18:55:30
DLL version V4.69b, compiled Apr 19 2013 18:55:27
Firmware: J-Link ARM V8 compiled Dec  1 2015 11:42:48
Hardware: V8.00
S/N: *** ***
Feature(s): RDI,FlashDL,FlashBP,JFlash,GDBFull
VTarget = 3.209V
Info: TotalIRLen = 4, IRPrint = 0x01
Found 1 JTAG device, Total IRLen = 4:
 #0 Id: 0x1F0F0F0F, IRLen: 04, IRPrint: 0x1, ARM7TDMI Core
Found ARM with core Id 0x1F0F0F0F (ARM7)
JTAG speed: 100 kHz
J-Link>

后来重启了，又不行了。想到重装jlink时ldconfig有问题，试试，

ldconfig: 无法创建临时缓冲文件 /etc/ld.so.cache~: 权限不够

su切换到root，无意试了试打开jlink，竟可以了。

(JLinkExe运行需root权限，同时只能运行一个jlink程序。)

(原来困扰我的jlink问题竟然一个su就解决了，汗，， )