The difference between Centos6 and Centos7 systems

Table of Contents

1. System type

2. Service management

3. File system

4. File structure

5. Desktop system

6. Host name

7. Check the system version

8. Time synchronization

9. Firewall

10. Login prompt

11. Character set

12. Time zone setting

13. Regional settings

14. grub (GRand Unified Bootloader)

15. Kernel

16. Database

17. Network card name

18. Nested virtualization technology

19. USB extension

20. Comparison chart

1. System type

The system type of centos6 is sysvinit (sysvinit is the init system of system V)

The system type of centos7 is systemd (systemed is the latest initialization system intt of the Linux system. The design goal of systemed is to overcome the inherent shortcomings of sysvinit, thereby efficiently improving the startup speed of the system).

You can check the system type through pstree -p. The first process of centos6 is init (pid=1), and the first process of centos7 is systemd (pid=1).

centos6 starts in a certain order and starts very slowly; centos7 starts in parallel and starts quickly.
In fact, many differences between centos6 and 7 are related to the system type sysvinit/systemd.

2. Service Management

centos6: uses service and chconfig management services (service service start/stop/restart/status/reload)
centos7: Use systemctl to manage services, but you can also use service and chconfig commands (systemctl start/stop/restart/reload service)

3. File system

centos6.X: The default file system is EXT4 (Fourth EXtended filesystem). The capacity of a single file system of EXT4 reaches 1EB (1,048,576TB, 1EB=1024PB, 1PB=1024TB), and the size of a single file reaches 16TB (4K block size); supported Unlimited number of subdirectories.
centos7.X: The default file system is XFS. The size is 9EB and the maximum file system size is 18EB.

You can use blkid /dev/sda1 to view the file system

[root@centos7 ~]# blkid /dev/sda1
/dev/sda1: UUID="d617fdc4-033b-431e-96d5-b106bbc9461d" TYPE="xfs"

4. File structure

centos6: /bin, /sbin, /lib, /lib64 are under /
centos7: /bin, /sbin, /lib, /lib64 are under /usr

5. Desktop system

centos6：GNOME 2.x
centos7: GNOME 3.x (GNOME Shell)

6. Host name

centos6: The configuration file is /etc/sysconfig/network (permanent settings)
centos7: The configuration file is /etc/hostname (permanent setting) and you can also use the command to set it permanently: hostnamectl set-hostname hostname #hostname is a new hostname management tool

7. Check system version

All redhat series (centos) can use cat /etc/redhat-release

centos7 can also use cat /etc/os-release to support the unified release version name and version number file of all systemd systems. This can be used to test ubuntu16 and 18; you can also use cat /proc/version to view the system version

[root@localhost ~]# cat /etc/os-release
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"

8. Time synchronization

centos6: using ntp
centos7: Using chrony can also use ntp

9. Firewall

centos6: iptables firewall
centos7: firewalld firewall

cat /etc/issue #Some production environments will clear this file. Please analyze the specific situation in detail.

[root@centso7 ~]# cat /etc/issue
\S
Kernel \r on an \m

11. Character set

centos6: use /etc/sysconfig/i18n
centos7: use /etc/local.conf

Centos7 can also use the character set management tool localectl to set it. localctl set-locale LANG=zh_CN.UTF-8 #localectl is a new character management tool

[root@centos7 ~]# cat /etc/locale.conf
LANG="zh_CN.UTF-8"

12. Time zone setting

centos6: in /etc/sysconfig/clock
centos7: There is no such configuration file, you need to use timedatectl to set it

[root@centos7 ~]# timedatectl
      Local time: Monday 2023-11-13 11:38:33 CST
  Universal time: 1 2023-11-13 03:38:33 UTC
        RTC time: 1 2023-11-13 02:34:26
       Time zone: Asia/Shanghai (CST, + 0800)
     NTP enabled: yes
NTP synchronized: no
 RTC in local TZ: no
      DST active: n/a

13. Regional Settings

centos6:

vim /etc/sysconfig/i18n LANG="ja_JP.utf8"
/etc/sysconfig/i18n
locale

centos7:

localectl set-locale LANG=ja_JP.utf8
localectl status

14.grub（GRand Unified Bootloader）

centos6: using grub
centos7: using grub2

The name of the configuration file has changed. In grub, the configuration file is grub.conf or menu.lst (a soft link to grub.conf). In grub2, it is renamed grub.cfg.