Linux file and directory management command base

Posted by jeevan_y21 on Mon, 06 Apr 2020 12:49:00 +0200

1. Directory structure

Everything starts from the root '/', which is the vertex of all directories

2. Relationship between partition and directory

  • One by one correspondence between partition and directory in Windows
  • Directories and partitions in Linux are separate.
    • Different disks are represented by letters
    • Different zones are represented by numbers
      • IDE disk:
        • Different disk representations
          • For example: hda1, hda2
        • Different partition representation methods
          • For example: hda1, hda2
      • SAS/SATA/SCSI/SSD disks
        • Different disk representations
          • sda，sdb.....
        • Different partition representation methods
          • sda1，sda2....
  • By default, the partition in Linux is inaccessible, prison and black box are inaccessible.
    • There is a function that links the directory / etc / to / dev/sda1, which is called mount

2.1, Mount

Find an entrance for the zone and open a door or window for the zone.

2.2 mount point

The directory name of the partition entry, / etc is the mount point of / dev/sda1

2.3 mount command and operation

  • Mount mount

    • Usage: mount device name mount directory

      [root@oldboyedu ~]# ls /mnt/
hgfs
[root@oldboyedu ~]# cd /dev/cdrom
-bash: cd: /dev/cdrom: Not a directory
#-bash:cd:/dev/cdrom: not a directory
[root@oldboyedu ~]# mount /dev/cdrom /mnt/
mount: /dev/sr0 is write-protected, mounting read-only
#mount:/dev/sr0 is write protected and mount is read-only
[root@oldboyedu ~]# ll /mnt/
total 694
-rw-rw-r--. 1 root root     14 Sep 10  2019 CentOS_BuildTag
drwxr-xr-x. 3 root root   2048 Sep  6  2019 EFI
-rw-rw-r--. 1 root root    227 Aug 30  2017 EULA
-rw-rw-r--. 1 root root  18009 Dec 10  2015 GPL
drwxr-xr-x. 3 root root   2048 Sep 10  2019 images
drwxr-xr-x. 2 root root   2048 Sep 10  2019 isolinux
drwxr-xr-x. 2 root root   2048 Sep  6  2019 LiveOS
drwxrwxr-x. 2 root root 671744 Sep 12  2019 Packages
drwxrwxr-x. 2 root root   4096 Sep 12  2019 repodata
-rw-rw-r--. 1 root root   1690 Dec 10  2015 RPM-GPG-KEY-CentOS-7
-rw-rw-r--. 1 root root   1690 Dec 10  2015 RPM-GPG-KEY-CentOS-Testing-7
-r--r--r--. 1 root root   2883 Sep 12  2019 TRANS.TBL

  • Uninstall: umount

    • Usage: you need to go back to the directory above the mount point and enter the umount directory

      [root@oldboyedu ~]# ll /mnt/
total 694
-rw-rw-r--. 1 root root     14 Sep 10  2019 CentOS_BuildTag
drwxr-xr-x. 3 root root   2048 Sep  6  2019 EFI
-rw-rw-r--. 1 root root    227 Aug 30  2017 EULA
-rw-rw-r--. 1 root root  18009 Dec 10  2015 GPL
drwxr-xr-x. 3 root root   2048 Sep 10  2019 images
drwxr-xr-x. 2 root root   2048 Sep 10  2019 isolinux
drwxr-xr-x. 2 root root   2048 Sep  6  2019 LiveOS
drwxrwxr-x. 2 root root 671744 Sep 12  2019 Packages
drwxrwxr-x. 2 root root   4096 Sep 12  2019 repodata
-rw-rw-r--. 1 root root   1690 Dec 10  2015 RPM-GPG-KEY-CentOS-7
-rw-rw-r--. 1 root root   1690 Dec 10  2015 RPM-GPG-KEY-CentOS-Testing-7
-r--r--r--. 1 root root   2883 Sep 12  2019 TRANS.TBL
[root@oldboyedu ~]# cd /mnt/
[root@oldboyedu /mnt]# umount /mut
umount: /mut: mountpoint not found
[root@oldboyedu /mnt]# umount /mnt
umount: /mnt: target is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
#umount:/mnt:target is busy. (in some cases, the device is found by lsof (8) or fuser (1)
[root@oldboyedu /mnt]# cd ..
[root@oldboyedu /]# umount /mnt
[root@oldboyedu /]# ll /mnt/
total 0
drwxr-xr-x. 2 root root 6 Apr  4 18:22 hgfs

  • View mount

    [root@oldboyedu ~]# df -h
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        1.9G     0  1.9G   0% /dev
tmpfs           1.9G     0  1.9G   0% /dev/shm
tmpfs           1.9G   12M  1.9G   1% /run
tmpfs           1.9G     0  1.9G   0% /sys/fs/cgroup
/dev/sda3        19G  2.0G   18G  11% /
/dev/sda1       253M  161M   93M  64% /boot
tmpfs           378M     0  378M   0% /run/user/0
# Total size of device name use size remaining use% mount point

2.4 standardization of FHS catalogue

  • The root directory "/" is mounted on the first disk. System related content

  • "/ usr" directory is mounted on the second disk with user related content

    [root@oldboyedu ~]# ls -ld /bin /lib /sbin /tmp
lrwxrwxrwx.  1 root root    7 Apr  4 18:05 /bin -> usr/bin
lrwxrwxrwx.  1 root root    7 Apr  4 18:05 /lib -> usr/lib
lrwxrwxrwx.  1 root root    8 Apr  4 18:05 /sbin -> usr/sbin
drwxrwxrwt. 11 root root 4096 Apr  6 17:30 /tmp
[root@oldboyedu ~]# ls -ld /usr/bin /usr/lib /usr/sbin /usr/tmp
dr-xr-xr-x.  2 root root 28672 Apr  4 18:23 /usr/bin
dr-xr-xr-x. 29 root root  4096 Apr  4 18:06 /usr/lib
dr-xr-xr-x.  2 root root 12288 Apr  4 18:23 /usr/sbin
lrwxrwxrwx.  1 root root    10 Apr  4 18:05 /usr/tmp -> ../var/tmp

3. Directory structure of linux

3.1 Linux directory definition

  • Marked with **** is the key memory
[root@oldboyedu /]# tree -L 1 /
/
├── bin -> usr/bin      #binaies, store command related*****
├── boot                #Boot partition, system kernel and boot program*****
├── dev					#Device, the directory where the device partition is located*****
├── etc					#Binary package configuration path
├── home				#Home directory of ordinary users*****
├── lib -> usr/lib		#32-bit library file
├── lib64 -> usr/lib64	#64 bit library file
├── media				#media
├── mnt					#Temporary mount point*****
├── opt					#option optional package (custom)
├── proc				#Virtual file system, directory for storing process and kernel information*****
├── root				#Administrator's home directory*****
├── run					#Running program related information file
├── sbin -> usr/sbin	#Directory of system binaies administrator command*****
├── srv					#The directory of the data serving the user
├── sys					#Virtual file system, directory for storing process and kernel information
├── tmp					#Temporary files sitting in directory*****
├── usr					#Directory of system software and user related programs, the second level directory*****
└── var					#Changeable data*****

4. / etc system initialization and setting related files

4.1. Configuration file of network card / etc / sysconfig / network scripts / ifcfg-eth0: used to configure files for Internet access

  • NIC name

    • CentOS7: ems33
    • Before CentOS 7: eth0 is the first network card eth1 is the second network card

  • Graphical configuration command:

    • CentOS7: nmtui
    • CentOS6: setup

  • Profile content

    [root@oldboyedu ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 
TYPE=Ethernet		#NIC type 
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none 		#Enable address protocol – static: static protocol – bootp: protocol – dhcp: Protocol - none: do not specify protocol [preferably]
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=eth0
UUID=a183d342-6fb0-4adc-8aba-7dced2f24643
DEVICE=eth0			#Network card interface name 
ONBOOT=yes			#Whether yes|no is activated when the system starts
IPADDR=10.0.0.200	 #IP address of network card 
PREFIX=24			#Subnet mask 24 = 255.255.255.0
GATEWAY=10.0.0.254	 #Network card gateway address
DNS1=112.100.100.100  #Network card DNS address 
IPV6_PRIVACY=no

4.2, / etc/resolv.conf Linux system DNS client configuration file

  • DNS Domain Name System

    • Function: the domain name entered in the browser is resolved to the IP address of the server, and then the server can be found to provide content
    • A long time ago, I couldn't remember IP0.0.0.200 when I was online....
    • At last, DNS was invented. The public resolution server resource requests its IP address if it wants to resolve
    • Important functions: the domain name entered in the browser is resolved to the IP address of the server, and there are many other functions.
    • The / etc/resolv.conf configuration file of DNS has been basically abandoned, which is replaced by DNS1=112.100.100.100 in the network card configuration file
    • As long as it is set in the network card configuration, it will be automatically updated to / etc/resolv.conf
    • But if you update the / etc/resolv.conf file first, the network card will be automatically cleared before
    [root@oldboyedu ~]# echo "nameserver 1.1.1.1" >> /etc/resolv.conf 
[root@oldboyedu ~]# cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 112.100.100.100
nameserver 1.1.1.1
[root@oldboyedu ~]# systemctl restart network
[root@oldboyedu ~]# cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 112.100.100.100

4.3/etc/hosts system local DNS resolution file

10.0.0.200 www.oldboyedu.com
10.0.0.201 www.baidu.com
 Everyone's computer must have a HOSTS for parsing.
  • When the browser re enters www.baidu.com, the priority is to find hosts for parsing.
  • The local DNS configuration file hosts takes precedence over the DNS resolution of the public network.
  • LAN developer test.

4.4/etc/fstab: configure the files automatically mounted by the boot device

  • The device can only be used after being hung. Have we ever mounted the root / boot?

    • The system automatically mounts the partition when we install the system

  • The automount file is / etc/fstab

  • For example, insert a U disk, and hope to access it directly after the next boot. It needs to be configured in / etc/fstab

    [root@oldboyedu ~]# cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Sat Apr  4 18:04:58 2020
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=63ff48bb-a38e-4a8a-afad-f24d25c7e442 /           xfs     defaults      0              0
UUID=00efac36-5fb3-4fcd-9249-a6210a52b5f0 /boot       xfs     defaults      0              0
UUID=9aa96766-7dd9-4fd4-979c-30ac56a20d57 swap        swap    defaults      0              0
//Device name (UUID) mount point file system type mount parameter whether to back up whether to power on check disk

    • View device UUID

      • blkid

        [root@oldboyedu ~]# blkid
/dev/sda3: UUID="63ff48bb-a38e-4a8a-afad-f24d25c7e442" TYPE="xfs" 
/dev/sda1: UUID="00efac36-5fb3-4fcd-9249-a6210a52b5f0" TYPE="xfs" 
/dev/sda2: UUID="9aa96766-7dd9-4fd4-979c-30ac56a20d57" TYPE="swap" 
/dev/sr0: UUID="2019-09-11-18-50-31-00" LABEL="CentOS 7 x86_64" TYPE="iso9660" PTTYPE="dos"

  • Set up auto mount

    [root@oldboyedu ~]# cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Sat Apr  4 18:04:58 2020
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=63ff48bb-a38e-4a8a-afad-f24d25c7e442 /                       xfs     defaults        0 0
UUID=00efac36-5fb3-4fcd-9249-a6210a52b5f0 /boot                   xfs     defaults        0 0
UUID=9aa96766-7dd9-4fd4-979c-30ac56a20d57 swap                    swap    defaults        0 0
UUID="2019-09-11-18-50-31-00"             /media                  iso9660 defaults        0 0

    Restart the server to view the directory (online environment cannot restart the server)

    [root@oldboyedu ~]# mount /dev/cdrom /media/
#Manually mount to the auto mounted directory, remember not to restart
mount: /dev/sr0 is write-protected, mounting read-only
[root@oldboyedu ~]# ll /media/
total 694
-rw-rw-r--. 1 root root     14 Sep 10  2019 CentOS_BuildTag
drwxr-xr-x. 3 root root   2048 Sep  6  2019 EFI
-rw-rw-r--. 1 root root    227 Aug 30  2017 EULA
-rw-rw-r--. 1 root root  18009 Dec 10  2015 GPL
drwxr-xr-x. 3 root root   2048 Sep 10  2019 images
drwxr-xr-x. 2 root root   2048 Sep 10  2019 isolinux
drwxr-xr-x. 2 root root   2048 Sep  6  2019 LiveOS
drwxrwxr-x. 2 root root 671744 Sep 12  2019 Packages
drwxrwxr-x. 2 root root   4096 Sep 12  2019 repodata
-rw-rw-r--. 1 root root   1690 Dec 10  2015 RPM-GPG-KEY-CentOS-7
-rw-rw-r--. 1 root root   1690 Dec 10  2015 RPM-GPG-KEY-CentOS-Testing-7
-r--r--r--. 1 root root   2883 Sep 12  2019 TRANS.TBL


    Connecting to 10.0.0.200:22...
Connection established.
To escape to local shell, press 'Ctrl+Alt+]'.

WARNING! The remote SSH server rejected X11 forwarding request.
Last login: Mon Apr  6 17:58:06 2020 from 10.0.0.1
[root@oldboyedu ~]# ll /media/
total 694
-rw-rw-r--. 1 root root     14 Sep 10  2019 CentOS_BuildTag
drwxr-xr-x. 3 root root   2048 Sep  6  2019 EFI
-rw-rw-r--. 1 root root    227 Aug 30  2017 EULA
-rw-rw-r--. 1 root root  18009 Dec 10  2015 GPL
drwxr-xr-x. 3 root root   2048 Sep 10  2019 images
drwxr-xr-x. 2 root root   2048 Sep 10  2019 isolinux
drwxr-xr-x. 2 root root   2048 Sep  6  2019 LiveOS
drwxrwxr-x. 2 root root 671744 Sep 12  2019 Packages
drwxrwxr-x. 2 root root   4096 Sep 12  2019 repodata
-rw-rw-r--. 1 root root   1690 Dec 10  2015 RPM-GPG-KEY-CentOS-7
-rw-rw-r--. 1 root root   1690 Dec 10  2015 RPM-GPG-KEY-CentOS-Testing-7
-r--r--r--. 1 root root   2883 Sep 12  2019 TRANS.TBL

4.5, / etc/issue and / etc/issue.net: display kernel parameter file in local window

Clear the contents of these two documents

[root@oldboyedu ~]# > /etc/issue
[root@oldboyedu ~]# > /etc/issue.net

4.6. / etc / RedHat release: view the system version

[root@oldboyedu ~]# uname -r
3.10.0-1062.18.1.el7.x86_64
[root@oldboyedu ~]# cat /etc/redhat-release 
CentOS Linux release 7.7.1908 (Core)
[root@oldboyedu ~]# cat /etc/os-release #This file is more detailed and complex
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

4.7, / etc/sysctl.conf: Linux kernel parameter setting file

Linux kernel configuration and optimized files

4.8, / etc/init.d: directory of software startup program (before CentOS7)

4.9, / etc/initab: set the startup level and start the corresponding level script file (before CentOS7)

[root@oldboyedu ~]# cat /etc/inittab 
# inittab is no longer used when using systemd.
#
# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
#
# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
#
# systemd uses 'targets' instead of runlevels. By default, there are two main targets:
#
# multi-user.target: analogous to runlevel 3
# graphical.target: analogous to runlevel 5
#
# To view current default target, run:
# systemctl get-default
#
# To set a default target, run:
# systemctl set-default TARGET.target
#

  • Linux system run level description:

    Operation level Grade level
    0 Shutdown
    1 Single user mode (used to retrieve the administrator password)
    2 No NFS, multi-user mode
    3 Command line mode text mode
    4 not used
    5 Graphic mode desktop mode
    6 restart

  • View run level

    • CentOS6:

      • runlevel

        [root@oldboyedu ~]# runlevel 
N 3

    • CentOS7:

      • who -r

        [root@oldboyedu ~]# who -r
         run-level 3  2020-04-06 18:02

      • systemctl get-default

        [root@oldboyedu ~]# systemctl get-default 
multi-user.target

  • CentOS7 run level

    [root@oldboyedu ~]# ll /usr/lib/systemd/system  | grep level | grep -v wants
lrwxrwxrwx. 1 root root   15 Apr  4 18:22 runlevel0.target -> poweroff.target
lrwxrwxrwx. 1 root root   13 Apr  4 18:22 runlevel1.target -> rescue.target
lrwxrwxrwx. 1 root root   17 Apr  4 18:22 runlevel2.target -> multi-user.target
lrwxrwxrwx. 1 root root   17 Apr  4 18:22 runlevel3.target -> multi-user.target
lrwxrwxrwx. 1 root root   17 Apr  4 18:22 runlevel4.target -> multi-user.target
lrwxrwxrwx. 1 root root   16 Apr  4 18:22 runlevel5.target -> graphical.target
lrwxrwxrwx. 1 root root   13 Apr  4 18:22 runlevel6.target -> reboot.target
-rw-r--r--. 1 root root  761 Mar 18 07:46 systemd-update-utmp-runlevel.service

    • Switch operation level

      [root@oldboyedu ~]# systemctl set-default graphical.target 
Removed symlink /etc/systemd/system/default.target.
Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/graphical.target.
[root@oldboyedu ~]# systemctl get-default 
graphical.target  #Graphical
[root@oldboyedu ~]# systemctl set-default multi-user.target 
Removed symlink /etc/systemd/system/default.target.
Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/multi-user.target.
[root@oldboyedu ~]# systemctl get-default 
multi-user.target #text

Topics: Linux CentOS network RPM

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