System Management and Umask

Time and TimeZone configuration

Set Time:

Timedatectl set-time "Time"

To view time zones:

Timedatectl List-timezones

Set the time zone:

Timedatectl Set-timezone Asia/shanghai

Network configuration

Static IP configuration:

Bootproto=static

Ipaddr=

netmask=

gateway=

dns1=

Dns2=

Onboot=yes

To modify the NIC name:

Change the cfg-enoxxxxxxx NIC name to Ifcfg-eth0

First turn off the device name acquired by the BIOS boot

Vim/etc/sysconfig/grub

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(RHGB: Do not display process startup information, delete and swipe to/boot/grub2/grub.cfg to display the start status of each service in the system boot)

Here, the boot is not in effect, and you need to run the following command to brush the configuration of Vim/etc/sysconfig/grub to/boot/grub2/grub.cfg

Grub2-mkconfig-o/boot/grub2/grub.cfg

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Vim/boot/grub2/grub.cfg Verify that the first configuration has been brushed into a startup item

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Next, you can modify the name of the NIC.

Cp/etc/sysconfig/network-script/ifcfg-enoxxxxxxxx/etc/sysconfig/network-script/ifcfg-eth0

Mv/etc/sysconfig/network-script/ifcfg-enoxxxxxxxx/etc/sysconfig/network-script/ifcfg-enoxxxxxxxx.bak

Vim/etc/sysconfig/network-script/ifcfg-eth0, change name=enoxxxxxxxx to Eth0

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Restart your computer.

Boot script

Example: empty all Files under the/tmp folder on boot

Vim/etc/rc.d/rc.local

chmod +x rc.local

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Add Users and groups (introduction)

Through the graphical interface:

Install a package that manages users first

Yum–y Install System-config-users

Enter the command in the graphical interface: System-config-users, bring up the user management interface

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Default Permissions

Umask (Matte)

By default, the maximum permissions for a folder are 777

By default, the maximum permissions for a file are 666

For example, an average user's umask is 002

The corresponding file 664

The corresponding folder 775

Root's Umask value is 022

The default permissions for files and folders are:

Folder: 777 binary code minus umask binary code

Files: 666 binary code minus umask binary code

Special permissions for files and folders

Suid and Sgid Special permissions

Suid: When Suid is applied to a binary file (command), then anyone who executes the command is temporarily used for command owner permissions and can only be applied to the executable file; u+s

Sgid: When Sgid is applied to a binary file, people and people temporarily have the command to have group permissions when executing the command, only on the executable file, and if Sgid is applied to a directory, then anyone who creates a file/directory in that directory will inherit the group of the directory itself; g+s

System Management and Umask