RHEL7/CentOS7 vs RHEL6/CentOS6 Differences

CentOS 7 has been changed from UNIX System V Init, which was conventionally used, to Systemd.
Therefore, the management command has changed significantly.

root/src/udev/udev-builtin-net_id.c

 * Two character prefixes based on the type of interface:
 *   en -- ethernet
 *   sl -- serial line IP (slip)
 *   wl -- wlan
 *   ww -- wwan
 *
 * Type of names:
 *   b<number>                             -- BCMA bus core number
 *   ccw<name>                             -- CCW bus group name
 *   o<index>[d<dev_port>]                 -- on-board device index number
 *   s<slot>[f<function>][d<dev_port>]     -- hotplug slot index number
 *   x<MAC>                                -- MAC address
 *   [P<domain>]p<bus>s<slot>[f<function>][d<dev_port>]
 *                                         -- PCI geographical location
 *   [P<domain>]p<bus>s<slot>[f<function>][u<port>][..][c<config>][i<interface>]
 *                                         -- USB port number chain

https://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-net_id.c#n20

• If bash-completion is installed, you can tab complement with systemctl like Cisco.
  For example, after systemctl there are candidates in two tabs
• When changing service file of systemd in RHEL 7 / CentOS 7, it is necessary to reflect it with “systemctl daemon-reload”.
• systemtl status UNIT result shows various information.

# systemctl status sshd.service
sshd.service - OpenSSH server daemon
   Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled)
   Active: active (running) since Month 2016-05-30 06:46:08 JST; 1h 45min ago
 Main PID: 1054 (sshd)
   CGroup: /system.slice/sshd.service
           mq1054 /usr/sbin/sshd -D

 May 30 06:46:08 centos7 systemd[1]: Started OpenSSH server daemon.
 May 30 06:46:08 centos7 sshd[1054]: Server listening on 0.0.0.0 port 22.
 May 30 06:46:08 centos7 sshd[1054]: Server listening on :: port 22.
 May 30 08:26:38 centos7 sshd[2592]: Accepted password for root from 192.168.56.1 port 52987 ssh2

• Even in 7 series you can use the ifconfig, route, netsat, arp commands by installing net-tools.
• There is no change in the setting file.

• It is recommended not to edit / etc / sysconfig / clock or / etc / localtime, but to set the time zone with the timedatectl command

Setting for system clock

# cp -p /etc/localtime /etc/localtime.org
# ln -sf /usr/share/zoneinfo/Asia/Tokyo /etc/localtime

Hardware clock setting

Corresponding to the fact that the time zone does not return to UTC upon restart

ZONE="Asia/Tokyo"
UTC=false

Even if LANG is set, LANG is overwritten by /etc/profile.d/lang.sh depending on the environment variable of the connection source terminal when ssh login is done.
For example, on the same server, LANG = C if LANG = C terminal, LANG = ja_JP.UTF-8 if LANG=UTF-8 terminal.
If you want to standardize on the server, you also need to set LANG in /etc/profile.

In /etc/profile, read /etc/locale.conf.

LANG="ja_JP.UTF-8"

...
#LANG
. /etc/locale.conf
export LANG

Even if LANG is set, LANG is overwritten by /etc/profile.d/lang.sh depending on the environment variable of the connection source, so if you want to unify it, add it to /etc/profile Also you need to set LANG.

• Logs are now saved with binary journal.
• It is also possible to set the rsyslog and save the log as text.