[Linux/LPIC] Memorandum

Overview

--Memo the content you were interested in as a memorandum ――Please note that the description is not exhaustive.

Super

Summary of package management command differences

Device mounting procedure

--Create partition - fdisk - parted --File system implementation - ext2~4 --ext2 does not support journals --Commands: mkfs, mke2fs --Parameter setting command: tune2fs - XFS --Command; mkfs.xfs --Mount --Description in fstab, etc.

GRUB configuration files and updates

• GRUB2
  • /etc/default/grub --Files in /etc/grub.d --Update command; grub-mkconfig

dmesg and systemd-journald

Creating a file system

--Ext2 is selected by default (all of the following use ext2 for type)

Runlevel target on systemd operation

ln default

--- b t (number the lines excluding blank lines) is the default

A command that can display the UUID of the device

• blkid
• lsblk

A command that can list all the set environment variables

• env
• printenv
• set

Exception usage of init (telinit)

--Usually change the runlevel using numbers - telinit 5 - init 5 --As an exception, if you want to reload "/ etc/inittab" without restarting the system, do the following: --telinit q or telinit Q --init q or init Q

High

Package management tool

rpm command

Only --f takes a file name as an argument. Only --p takes a package file name as an argument.

dpkg command

yum subcommand / zypper subcommand

--yum configuration file - /etc/yum.conf --/etc/yum.repos.d = Package acquisition source (repository) is set in the file in the directory --zypper config file =

apt-get subcommand (significantly different from yum and zypper)

apt-cache subcommand

ldd --Command to search library --You can use ldd/etc/ls to search for the library used by the command. --Command to update the cache file "/etc/ld.so.cache" of the shared library - ldconfig

Boot loader

function

--Called after booting the BIOS to boot the OS and kernel

Install command

• grub-install

• version

  • GRUB Legacy
  • GRUB2

• GRUB

• setting file - /boot/grub/grub.conf - /boot/grub/menu.list

• GRUB2

• setting file --/boot/grub/grub.cfg (do not edit directly) - /etc/default/grub - /etc/grub.d

MBR (Master Boot Record)

--Saved in 446 bytes of storage --The rest is the route table 16 bytes * 4 and 2 bytes boot signature

init program

--systemd subcommand collection --systemd command is systemctl --systemctl subcommand [Unit name]

Boot-related target directory

• /etc/systemd/system/default.target --A symbolic link is set in the above --Links cannot be overwritten, so prior deletion is required when making changes. --ln Filename Create a hard link with a link name --ln -s Filename Create a symbolic link with a link name --Runlevel and target compatibility table

Shell variables / environment variables

--Major premise --The value of the environment variable cannot be retained permanently with the export command, so it must be described in the configuration file. (.Zshrc for zsh, .bash_profile for bash) --Environment variable (path) --Search and execute from the directory set in the environment variable PATH (the so-called path is in the path) --export PATH = $ PATH: directory --If the command is in a directory that is in the path, you can execute it only by the command name without specifying the path where the command is stored. --Environment variables are provided for each user. For example, the environment variables used by user1 and user2 can have different values. --Environment variables (other than paths) --Some are set by default (USER, HOME, etc.) --Set with export environment variable name = "value"

--Change shell variables to environment variables --Set by export shell variable name (after all, with export environment variable name = "value")

tar (archive function)

--tar [option] [directory name] [file name] --When creating hoge.tar that archives aa, bb, cc, the description is as follows (The archive name is described first)

% tar cf hoge.tar aa bb cc

--- c (Create new archive) --- x (extract from archive) --- t (Display archive information) --It is not compressed, and if you keep the information before putting it together, it may be larger than the original file procedure.

cpio (Archive function)

--cpio [option] --- o (create a new archive) --- i (extract from archive) -- Accept only from standard input

% cpio -i <file name.cpio

grep command (search function)

--Search for various things from the process to the contents of the file --By default, the line corresponding to the search target is displayed.

tee (Standard input output destination is bifurcated)

% dmesg | tee -a log.txt

--Receive the standard output of dmesg as a standard input with a pipe, and add both the standard output (1) and log.txt. If you do not specify the option -a (probably an abbreviation for add), it will be overwritten (>).

ln (create link)

--ln [option] Link source Link destination --Create hard link without options --Hard link --A link that directly refers to the actual file --Director hard links cannot be created (to prevent the creation of circular directories) --Cannot be created on different partitions (because inodes are managed separately and may be duplicated) --Create symbolic link with option -s --Symbolic link --A link pointing to the location of the original file (like a shortcut in Windows)

File management on Linux

--Files (including directories) are managed using "file entity (data body)" and "inode" --inode is like a label --Files are deleted when inode (hard link) reaches 0

mv (move and rename files)

--Move the "test1.txt" file to the "dir1" directory in the current directory and rename the file to "test2.txt"

% mv test1.txt dir1/test2.txt

kill signal system

--kill [-signal name or-signal number] [process ID] --killall [-signal name or-signal number] --killall -s [-signal name or-signal number] --pkill [-signal name or-signal number] process name (command name) --pkill --signal [-signal name or-signal number] process name (command name) -* 15 (TERM) is selected if no signal is specified for killall and pkill.

Process monitoring

--ps [option] --There are BSD options without "-" and UNIX options starting with "-".

Docker

Main commands

File display system basic commands

Low

Virtual terminal control program

A means of using multiple terminals on one terminal by operating a program that controls virtual terminals instead of using a large number of terminal programs.

• screen
• tmux

VM virsh --A shell for working with libvirt (a library for open source virtualization management) --Various operations such as virtual machine resource management and virtual network management are possible --Command collection

chown, chgrp (belonging group)

--You can change the owned group --chown [-R]: group name file or directory --chgrp [-R] group name file or directory --Use the "-R" option to recursively change the owning user or group of the specified directory and the files under it. --If there is no "-R" option, change the owning group for directories only

chmod (permission)

--Three digits represent the status of users (U), groups (G), and others (O) --The situation is the total value of the following numbers --If it is 753, [Full authority (4 + 2 + 1)] [Read / execute (4 + 1)] [Write / execute (2 + 1)]

find

--Command to search files and directories under the specified directory --find [search starting directory] [search expression] [action]

Difference between snapshot and backup

Regular expression

Vi editor

--To execute Linux commands without exiting the vi editor, execute the following vi command in command mode. -:![Command] --Example:! Ls The left indicates that the ls command was executed in the current directory.

tail command

tr and sed

--Sed seems to be considered as upward compatible with tr

nice and nice

--Nice values ​​(priority) are both -20 to 19 (-20 is the highest priority and 19 is the lowest priority) --The default nice value if nothing is specified is 10 --The default reason value when nothing is specified is 0 --Nice value description method is different for each --In nice, -(hyphen) is accompanied, so -10 becomes --10. --In renice, -(hyphen) is not accompanied, so -10 becomes 10.

• No need for -p

Editor type

du and df

Symbolic links and hard links

fdisk, parted and mkfs

fstab and mtab

--mount is a mounting operation that embeds a disk device in a Linux directory and makes it usable.

tune2fs --Perform existing file system management operations --Different from mkfs in that it creates a file system

File system type

telinit --Try to change the runlevel.

UUID --UUID (Universally Unique Identifier) ​​is an identifier that uniquely identifies an object on software.

Block device

--Device files that transfer data in block units instead of character units when accessed --Commands that can display the UUID of the device