Shulou(Shulou.com)06/03 Report--

1, disk lvm management, complete the following requirements, and write the detailed process: centos7 environment

1)Create a VG named testvg with at least two PVs of 20 gigabytes in size; PE size of 16MB is required, and then create a logical volume testlv of 5 gigabytes in the volume group; mount to/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, requiring archlinux users to have files that cannot be lost

lvextend -l 7G /dev/testvg/testlv resize2fs /dev/testvg/testlv (Sync the original file system, for ext series, write device name here) xfs_growfs /mnt/users (For xfs, write mount point here)

3)Narrowing testlv to 3G requires that archlinux users 'files cannot 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 testlv and try to back up data based on the snapshot to verify the functionality of the snapshot

lvcreate -n testlv_snap -s -p r -L 1G /dev/testvg/testlv mkdir /mnt/snap mount testlv_snap /mnt/snap

Snapshot restore:

umount /mnt/users/ umount /mnt/snap/ lvconvert --merge /dev/testvg/testlv_snap centos6, centos 7, mount -o nouuid /dev/testvg/testlv_snap /mnt/snap

All restored:

lvremove /dev/testvg/testlv vgremove testvg pvremove /dev/sda6 /dev/sdc

2. Create a RAID1 device with 1G of free space, ext4 file system, and a free disk that can be automatically mounted to the/backup directory after booting.

Create 2 partitions sdb1, sdc1, sde for free disk, pay attention to type selection fd mdadm -C -a yes /dev/md0 -l 1 -n 2 -x 1 -c 1G /dev/sd{b1,c1,e} - x1 stands for 1 spare. cat /proc/mdstat You can view raid members mdadm -D /dev/md0 View detailed raid information mkfs.ext4 /dev/md0 mkdir /mnt/raid The file/etc/fstab should be installed automatically. mount -a

3. Briefly describe the TCP link establishment and disconnection process

Three handshakes and four waves.

Three handshakes:

The client accesses the server and sends SYN=1,seq=x sequence number to the server. The server responds by sending ack=x+1 SYN=1. ACK=1 seq=y sequence number The client sends ACK=1.seq=x+1 ack=y+1 to the server y+1 represents that the client receives the seq=y message sent by the server before and responds that the server wants the server to send y+1 next time.

Four waves:

The client sends the information of FIN=1,seq=u sequence number to the server, and the server responds with ACK=1, seq=v, ack=u+1 information to the client. The server finishes transmitting the data and sends FIN=1ACK=1 seq=w ack=u+1 to the client. The client sends ACK=1 seq=u+1 ack=w+1 to the server. The FIN flag bit is the end flag.

4. Briefly describe the difference between TCP and UDP

TCP and UDP work at the transport layer.

TCP is connection-oriented, that is, sending a data packet before transmitting data to test whether there is packet loss.

UDP is not connection-oriented, no test is directly sent out data

TCP sends data messages in sequence and numbers them.

UDP has no order, the first received in front, some data may be received later, this will cause data errors, is unreliable

TCP applies to mail transfer, downloads, file transfers

UDP applies to video, voice

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