uuid

记一次磁盘扩容失败并恢复

由 邮差的信 提交于 2020-01-28 08:13:11
扩容前： 然后准备给home扩容： 扩容前先备份一下: 分两步： 1.备份VG，这个是系统会自动备份的，文件在/etc/lvm/archive/目录下 2.备份superblock superblock记录了磁盘的格式、已经使用大小等等信息 dd if=/dev/mapper/centos-home of=./backup_before_add bs=4096 count=1 扩容 添加新硬盘后： fdisk /dev/sda 扩容完成 增加了500M 模拟错误 我遇到的错误是新添加的硬盘离线了，我模拟下把新加入的sdb磁盘删除，重启后显示如下错误： Warning: Device for PV uuid not found or rejected by a filter 来分析下原因： 本来名叫centos的vg是有sda2和sdb1共同组成的，共计4.5G，现在sdb磁盘找不到了，sdb1也就找不到了。 通过vi打开/etc/lvm/arichive/下最新的.vg文件可以印证这一点： 正确处理 Device for PV uuid not found的姿势 先说正确的处理方式： 1.先备份vg和superblock,vg系统自动备份了，superblock的备份还是通过dd命令 dd if=/dev/mapper/centos-home of=./backup_after

DLNA第一步UPnP协议栈

由 人走茶凉 提交于 2020-01-27 05:39:08
前面公司有DLNA项目，研究了一下，在网上关于DLNA的资源很少,就将自己的心得写出来，以供参考。 其它的关于DLNA的介绍就不多说，要了解DLNA需要了解upnp,因为DLNA在upnp之上，初学者可以从http://www.upnp.org下载upnp的资料.也欢迎大家加入197683240 DLNA交流群。 upnp 分为四步：发现 、 描述 、 控制 、 事件 发现 当一个 UPnP 的设备加入网络，并想知道什么 UPnP 服务在网络上可用，它发送一个发现消息多播地址 239.255.255.250 端口 1900 通过 UDP 协议。此消息包含一个头，类似于一个 HTTP 请求。该协议有时被称为为 HTTPU （ HTTP 通过 UDP ）： M-SEARCH * HTTP/1.1 ST: upnp:rootdevice MX: 3 MAN: "ssdp:discover" 所有其他UPnP设备或方案都必须回应此消息类似的消息发送回设备，使用UDP单播，宣布该设备或程序实现的UPnP型材。一个有趣的怪癖：发送UDP单播设备发现消息被送往港口。 对于每一个配置文件，它实现发送一条消息： HTTP/1.1 200 OK ST:upnp:rootdevice USN:uuid:1d8ec8a7-4736-4598-9950-9710c992e471::upnp

Platform-independent GUID generation in C++?

由 a 夏天 提交于 2020-01-27 03:24:48
问题 What is the best way to programmatically generate a GUID or UUID in C++ without relying on a platform-specific tool? I am trying to make unique identifiers for objects in a simulation, but can't rely on Microsoft's implementation as the project is cross-platform. Notes: Since this is for a simulator, I don't really need cryptographic randomness. It would be best if this is a 32 bit number. 回答1: If you can afford to use Boost, then there is a UUID library that should do the trick. It's very

Platform-independent GUID generation in C++?

由 瘦欲@ 提交于 2020-01-27 03:24:09
问题 What is the best way to programmatically generate a GUID or UUID in C++ without relying on a platform-specific tool? I am trying to make unique identifiers for objects in a simulation, but can't rely on Microsoft's implementation as the project is cross-platform. Notes: Since this is for a simulator, I don't really need cryptographic randomness. It would be best if this is a 32 bit number. 回答1: If you can afford to use Boost, then there is a UUID library that should do the trick. It's very

How should I store GUID in MySQL tables?

由 前提是你 提交于 2020-01-26 08:07:21
问题 Do I use varchar(36) or are there any better ways to do it? 回答1: My DBA asked me when I asked about the best way to store GUIDs for my objects why I needed to store 16 bytes when I could do the same thing in 4 bytes with an Integer. Since he put that challenge out there to me I thought now was a good time to mention it. That being said... You can store a guid as a CHAR(16) binary if you want to make the most optimal use of storage space. 回答2: I would store it as a char(36). 回答3: Adding to the

How should I store GUID in MySQL tables?

由 …衆ロ難τιáo~ 提交于 2020-01-26 08:02:06
问题 Do I use varchar(36) or are there any better ways to do it? 回答1: My DBA asked me when I asked about the best way to store GUIDs for my objects why I needed to store 16 bytes when I could do the same thing in 4 bytes with an Integer. Since he put that challenge out there to me I thought now was a good time to mention it. That being said... You can store a guid as a CHAR(16) binary if you want to make the most optimal use of storage space. 回答2: I would store it as a char(36). 回答3: Adding to the

How should I store GUID in MySQL tables?

由 拟墨画扇 提交于 2020-01-26 08:02:06
问题 Do I use varchar(36) or are there any better ways to do it? 回答1: My DBA asked me when I asked about the best way to store GUIDs for my objects why I needed to store 16 bytes when I could do the same thing in 4 bytes with an Integer. Since he put that challenge out there to me I thought now was a good time to mention it. That being said... You can store a guid as a CHAR(16) binary if you want to make the most optimal use of storage space. 回答2: I would store it as a char(36). 回答3: Adding to the

Can we use process.hrtime() as UUID in node.js?

由 房东的猫 提交于 2020-01-25 05:00:06
问题 Can we use process.hrtime() as universal unique id within the current process ? var uuid = parseInt(process.hrtime().join('')); 回答1: You can use process.hrtime() to create identifiers with low chance of collision, but they are not unique, especially not across application restarts (which matters if you persist any of them to a database or similar), and not when several threads/processes/instances are involved. From the documentation: These times are relative to an arbitrary time in the past,

Understanding long and short form of UUID

由 佐手、 提交于 2020-01-25 02:53:08
问题 I am trying to learn some bluetooth programming in android I have been able to make a rudimentary program that discovers and connects to a (currently just a single) development board with Bluetooth features built in I want to be able to send commands to the board as well as receive messages from it using RFCOMM I have been told that I will probably not be able to move any further without knowing the UUID for the board as well as the phone While digging around for this, I found out that the

Hash UUIDs without requiring ordering

由 强颜欢笑 提交于 2020-01-24 17:52:12
问题 I have two UUIDs. I want to hash them perfectly to produce a single unique value, but with a constraint that f(m,n) and f(n,m) must generate the same hash. UUIDs are 128-bit values the hash function should have no collisions - all possible input pairings must generate unique hash values f(m,n) and f(n,m) must generate the same hash - that is, ordering is not important I'm working in Go, so the resulting value must fit in a 256-bit int the hash does not need to be reversible Can anyone help?
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