Electronics global trade by HS code

List of the directory of this article:

• 1,Electronics global trade by HS code Detailed explanation of CentOS service program performance evaluation document
• 2, Why is the file system of df in linux much more than that of blkid
• 3. tmpfs file system in linux What is the full name
• 4, proc, sysfs ,Tmpfs,devpts all say what file system
• 5, What if the data modified in Linux is not written back to the disk?
• 6, What is linux's /dev/shm used for

CentOS service program performance evaluation document detailed explanation

1. Under Linux, we can use the uptime command, and this command does not need to use root permission. The uptime command has been installed in the system by default.

2. tomcat4 Tomcat Web Server service is used to support CAMS configuration management desk, self-service platform, Portal service platform and content billing authentication platform, etc.; all service program scripts in Linux system are It can be found in the "/etc/rc.d/init.d" folder, and each service corresponds to a script file.

3. For the ideal Linux memory page, the total amount of exchanges actually used should not be redundant to the amount of inactive (anonymous) memory pages. The amount of active (file) memory is equal to the amount of cache memory required by the kernel. Otherwise, the server performance cannot be improved. When the kernel needs more memory, the file memory marked as inactive will be discarded.

Why are there more df file systems in linux than blkid Many

zombie files: the deleted file has not released the corresponding space because the handle is occupied and not released. Mount point overlay: A large number of files already exist in the corresponding directory of the original file system.After mounting the new disk, the df command can be used to count the relevant space, but the su command cannot be counted.

Generally speaking, this situation is related to the differences in the file system. Because the size of the block may be different, the file occupation may also be different. As for the large capacity when mounting a USB flash drive, it may be another problem. I guess it may be caused by the calculation method.

df command parameter function in linux: check the disk space occupation of the file system. You can use this command to obtain information such as how much space is occupied on the hard disk and how much space is left at present. Syntax: df [Option] Description: The df command in linux can show the use of i-nodes and disk blocks in all file systems.

Yes, there are multiple commands in Linux that can be used to view the information of the file system.The following are some commonly used commands: df command: used to display the disk space usage of the file system, including used space, available space, file system type, etc.

How to clean up the linux disk when it is full? Regularly scan and compare important file systems to analyze those files that are often read and written #ls_lR/home; files.txt#difffilesold.txtfiles.txt predicts the growth of space by analyzing, and at the same time, you can consider reading and writing infrequently. The file is compressed to reduce the space occupied.

df can do a lot of operations on the disk. The detailed introduction of df is as follows: Syntax: df Description: The df command in linux can display the usage of i-nodes and disk blocks in all file systems.

What is the full name of the tmpfs file system in linux

1. It is a virtual memory file system, which is different from the traditional Ramdisk implemented in the form of a block device, and also It is different from Ramfs for physical memory. Tmpfs can use physical memory or swap partitions.

2. Tmpfs is a virtual memory file system, which is different from the traditional Ramdisk implemented in the form of block devices, and Ramfs for physical memory.

3, /dev/shm/ is the next very useful directory in linux, because this directory is not on the hard disk, but in the memory.Therefore, under Linux, there is no need to build ramdisk, and direct use of /dev/shm/ can achieve a good optimization effect.

proc, sysfs, tmpfs, devpts all say what file system

file system: file system is used to create and store A collection of software and data structures that store, retrieve, update and protect files. It is part of the operating system and can be regarded as an "organizer" responsible for managing all the files on the hard disk.

On the other hand, because Linux has good file system support (for example, it supports ExtFAT3romfs and other file systems) is a good platform for data, synchronization and replication, which lay a solid foundation for the development of embedded system applications.

The following file systems are currently supported by Linux: adfs, befs, cifs, ext extext, iso9660, kafs, minix, msdos, vfat, umsdos, proc, rei Serfs, swap, squashfs, nfs, hpfs, ncpfs, ntfs, affs, ufs. Options.

tmpfs is a file system (OS or some software will use it, such as oracle uses tmPfs), but it is memory-based, that is to say, the file system is mounted on memory rather than on the hard disk, so that the reading and writing of files on tmpfs is extremely efficient.

Now the default file system format of Redhat Linux is ext4.

What if the data modified in Linux is not written back to the disk?

1. It is the main disk cache used by the Linux kernel.

2. Click the arrow position logo in the lower left corner of the computer, and then select the startup terminal, enter the command Enter on the terminal, and then find the hard disk on the computer, of which sda is the first hard disk and sdb is the second hard disk.

3. Under Linux, you can use the fdisk command to create a new partition. The method is as follows: First, use the fdisk-l command to view the hard disk information. If the hard disk has spare space, it can be partitioned. Assuming that /dev/sdb is not used, fdisk/dev/sdb has an extended partition and a main partition, and the logical partition is created in the extended partition.

4. In the Linux system, configuration files are some parameters and options used to control the operation of the program. If there are some errors or incorrect settings in the configuration file, it may cause the program to fail to start or run improperly.

5. Execute sync data sync# This command writes the unwritten system buffer to the disk #containing modified i-node, delayed block I/O and read-write mapping files.

What is the use of linux's /dev/shm

/dev/shm is the next very useful directory of linux, which is the use of the Linux operating system A directory virtually generated by memory, the files in this directory are saved in memory, which is very efficient. Or this directory is used for memory mapping.

a shortcut channel of tmpfs. Map part of the memory capacity. If the memory loses power and the data is lost, it will also remap the memory. Every time you turn on/dev, the things will be reset. Completely delete and recreate.

/dev/shm/ is the next very useful directory in Linux, because this directory is not on the hard disk, but in memory.Therefore, under Linux, there is no need to build ramdisk, and direct use of /dev/shm/ can achieve a good optimization effect.