vm creation, snapshots, raid create a TCP three-way handshake and four wave

1, lvm disk management to complete the requirements below, and write a detailed process: centos7 environment

1) Create a size of the at least two PV VG is composed of named testvg of 20G; PE claim size 16MB, then the size of 5G created logical volume in the volume group testlv; to mount / users directory

        pvcreate  /dev/sd{a6,c}

        vgcreate  -s 16M  testvg  /dev/sd{a6,c}

        lvcreate  -n  testlv  -L  5G  testvg 

        mkfs.ext4  /dev/testvg/testlv

        mkdir  /mnt/users

        mount  /dev/testvg/testlv  /mnt/users/

2) extend testlv to 7G, archlinux requires the user's file can not be lost

        lvextend  -l  7G   /dev/testvg/testlv

        resize2fs   /dev/testvg/testlv      (同步原来的文件系统，适用于ext系列，这里写设备名称)

        xfs_growfs  /mnt/users   （适用于xfs，这里写挂载点）

3) testlv to shrink 3G, archlinux requires the user's file can not be lost

        umount   /mnt/users/

        e2fsck  -f  /dev/testvg/testlv

        resize2fs   /dev/testvg/testlv   3G

        lvreduce  -L  3G   /dev/testvg/testlv 

         mount  /dev/testvg/testlv  /mnt/users/

4) Create a snapshot of the testlv, and try to function-based snapshot backup data validation snapshot

        lvcreate  -n  testlv_snap  -s  -p r    -L  1G  /dev/testvg/testlv 

        mkdir  /mnt/snap

        mount  testlv_snap   /mnt/snap

Restore Snapshot:

        umount   /mnt/users/

        umount  /mnt/snap/

        lvconvert  --merge  /dev/testvg/testlv_snap

        以上是centos6，如果是centos7，mount  -o  nouuid  /dev/testvg/testlv_snap   /mnt/snap

Full Restore:

        lvremove  /dev/testvg/testlv

        vgremove  testvg

        pvremove  /dev/sda6  /dev/sdc

2, to create a free space for the apparatus 1G of RAID1, ext4 file system, there is a spare disk, can be switched to automatic loading / backup directory

        创建2个分区sdb1，sdc1，sde为空闲盘，注意类型选择fd

        mdadm  -C  -a  yes  /dev/md0   -l 1  -n  2  -x  1  -c 1G  /dev/sd{b1,c1,e}            -x  1  代表1个备用的

        cat  /proc/mdstat    可以查看raid成员

        mdadm  -D   /dev/md0   查看详细的raid信息

        mkfs.ext4  /dev/md0

        mkdir  /mnt/raid

        开机可自动挂载要写在/etc/fstab文件里

        mount  -a

3, brief TCP connection establishment and disconnection process

Three-way handshake and four wave

Three-way handshake:

 客户端访问服务器

 客户端发送SYN=1,seq=x序号给到服务器

 服务器回应发送ack=x+1  SYN=1. ACK=1 seq=y序号给客户端

 客户端发送ACK=1.seq=x+1  ack=y+1给服务器

 y+1代表客户端收到之前服务器发送的seq=y的信息，并且回应服务器希望服务器下次发送y+1

Four wave:

客户端向服务器发送FIN=1,seq=u序号的信息给服务器

服务器回应ACK=1，seq=v，ack=u+1的信息给客户端

服务器把数据传完，发送FIN=1ACK=1  seq=w  ack=u+1给客户端

客户端发送ACK=1  seq=u+1 ack=w+1给服务器

FIN标记位是结束标记

4 distinction, TCP and UDP DESCRIPTION

TCP, UDP operate at the transport layer

TCP connection-oriented, that is, before the transfer of data to send data packets to test whether loss

Connectionless UDP does not directly send data out of the test

TCP send data packets have order, are numbered.

UDP does not order, first received earlier, probably after some data will be sent to receive, thus causing data errors are not reliable

TCP applies to e-mail, downloading, file transfer

UDP used in video, voice

vm creation, snapshots, raid create a TCP three-way handshake and four wave

Guess you like