Shulou(Shulou.com)06/02 Report--

1. Linux system directory version naming rules: kernel version consists of three parts: major version number, minor version number, last version number development version: the second digit is odd stable version; the second digit is even file and directory naming rules:

The file name is up to 255byte long, 4095 bytes including the path, and is case-sensitive.

File name: letters, numbers, underscores, dots normal files-(black) directory files d (blue) link files l (bright blue) special files cd (yellow) configuration files .conf log files .log system log files .syslog system configuration files .cfg system files .i386 script files .sh file system files and directories are organized into a single root inverted tree structure

We can also view the tree structure with the tree command

The / boot directory contains system startup files (boot loader), such as Grub,Lilo or Kernel, and configuration files such as initrd,system.map. This directory contains kernel, firmware, and system-related files. / sbin contains the binaries and management tools necessary for the operation and operation of the system, mainly executables. Similar to the EXE file under WINDOWS. / bin contains binaries and utility programs in single-user mode, such as cat,ls,cp commands. / lib contains the library files needed to run the binaries under the / sbin and / bin directories. / dev contains the necessary system files and drives. / etc contains the system configuration file, the directories under it, such as / etc/hosts, / etc/resolv.conf, nsswitch.conf, as well as system defaults, network configuration files, and so on. And some configuration files for systems and applications. / home each user has a separate directory under this directory with their user name commands, where the user's personal settings files, especially those ending in profile, are saved. There are exceptions, however, where the root user's data is not in this directory, but is stored separately in the root path and in a separate / root folder. / media is a general mount point for all removable devices such as optical drives, USB external disks, and floppy disks. / mnt temporary file system mount point. For example, if you don't want to mount a drive for a long time, but just temporarily mount a flash drive and bake a MP3 for a while, you should mount it in this location. / opt in Linux systems, this directory is not used much, and opt is short for optional system package (Optional Software Packages). This directory is much more widely used in UNIX systems such as Sun Solaris. / usr user data directory, which contains utilities and applications that belong to the user. There are many important, but not critical, file system mounts below this path. Here, you will find a new bin, sbin, and lib directory that contains non-critical user and system binaries, as well as related libraries and shared directories, as well as some library files. / usr/sbin contains non-essential and not particularly important system binaries and network utilities in the system. / usr/bin contains the user's non-essential and not particularly important binaries. / usr/lib holds the library files needed for the binaries in / usr/sbin and / usr/bin. / usr/share "platform independent" shared data directory. / usr/local is the secondary directory under / usr, where local system data, including system binaries and runtime, is stored. / var this path usually holds including system logs, printer background files (spool files), timing tasks (crontab), mail, running processes, process lock files, and so on. This directory needs to pay special attention to daily inspection and maintenance, because the size of the files in this directory may grow so fast that it will quickly fill the hard disk, which will lead to all kinds of strange problems in the system. / tmp as the name implies, this is a temporary folder dedicated to storing temporary files, and the "temporary" files in this directory are emptied each time the system is rebooted. Similarly, / var/tmp also holds temporary files. The only difference between the two is that the files saved in the latter / var/tmp directory will be protected by the system, and the files in this directory will not be emptied after the system reboot. The / proc directory is a virtual (psuedo, pseudo) file system that resides in the system memory, where the system kernel and process information is stored in text format. two。 File metadata information and viewing data in the file system can be divided into two categories: 1) data (data): data in ordinary files 2) metadata (metadata): system data used to describe the characteristics of a file, such as access rights, file owner, and the distribution of file data blocks, specific time to view, and so on. You can use the * * stat** command to view the file metadata:

File file name Size file size IO Block IO block size regular file here is the display file type, this is a normal file Device device Inode Inode node number Links is linked times Access (1) access rights Uid uid number and owner Gid gid number and subordinate group Access (2) last access time of Modify file change time of Chang file if you want to change timestamp information You can use the * touch** command

* * the touch** command can be used to update the access and modification time, and can also be used to create new files (please use help or man help flexibly) if you want to modify the timestamp information you want, you can use the * * touch-t command * * here is an example: first use touch to create an empty file f1.txt, and use the * * stat** command to view metadata

We use the * * touch-tasking * command to change it to the time we want, and use * * stat** to view

We found that the time has changed, and the change (file modification time) has become the time for us to modify the file. Soft links, hard links before figuring out soft links and hard links, we need to know a concept: the inode table of the index node (inode-- index node) contains a list of all files in the file system. An inode contains the original information about the file. To put it succinctly, people refer to the file through the file name, while the directory is the mapping between the file name and the file inode number in the directory.

As shown in the figure above, the inode table structure is also a tree structure. Similar to search tree, we can use * * ll-iTunes * to see the inode of a file. When it comes to a file, we can use a command called * * cp** to copy a file or folder. We can use help or man help to see all the uses of cp, but using the cp command is to copy the file again and point to it with a new inode. We can use soft and hard links not to copy physical files hard links create hard links will add additional entries to reference files, corresponding to a physical file on the same file system, the inode number is the same, the number of links increases if deleted, the number of links decreases, when the number of links is 00:00, we can use the command * * ln** to create hard links

We found that when the hard link is not created, the number of links is only 1, when the hard link is created, the two inode numbers are the same, and the number of links increases to 2 symbols (soft) link one symbolic link points to another file, the content of the symbolic link is the name of the file it applies, the directory can be carried out and can be cross-partitioned, and we can obviously know if the original file is deleted. If the link fails, we can use * * ln-slots * to create a soft connection.

We can see clearly that when f1.txt is deleted, the link is invalid, but the link only points to the path, so if f1.txt comes back, the link is still useful 4. Linux file management class commands linux file management class commands a lot of commands Probably commonly used are as follows: ls: list directories cd: switch directories pwd: show the current directory mkdir: create a new directory rmdir: delete an empty directory cp: copy files or directories rm: remove files or directories mv: move files and directories, or modify the names of files and directories 5. Vim some small exercises

If you are used to using vi and want to change it to vim, you can use the alias vi=vim command. If you want to change it permanently, you can see my previous article.

1) copy / etc/profile to / tmp/ directory, delete the white space character at the beginning of the line in / tmp/profile file with the find and replace command * enter / tmp/profile using vim, type: 1s/ g to explain: 1 represents the first line, s represents substitute replacement, and then represents to convert the space to nothing, that is to delete the space G means replace if the whole line satisfies the conditions 2) set tab indentation to 4 characters in vim * to change the formatting in vim, you can change * * set ts=4 in .vimrc (note: ts is the abbreviation of tabstop, let TAB be 4 spaces wide) set expandtab this method requires restarting vim or you can enter: set ts=4:set expandtab:%retab after entering the file using vim!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.