CentOS

CentOS(8), RedHat, Amazon Linux2

hostnamectl

# hostnamectl
Static hostname: Hostname01

# hostnamectl set-hostname NewHostName

timedatectl

# timedatectl
 Local Time    : MDAY YYYY-MM-DD: HH:mm:ss UTC 
 Universal Time: MDAY YYYY-MM-DD: HH:mm:ss UTC
 Time zone: n/a (UTC, +000)

# timedatectl set-timezone Asia/Tokyo
# timedatectl
 Local Time    : MDAY YYYY-MM-DD: HH:mm:ss JST
 Universal Time: MDAY YYYY-MM-DD: HH:mm:ss UTC
 Time zone     : Asia/Tokyo (JST, +0900)

Amazon Linux2 - Packages

# amazon-linux-extras list | grep package

# amazon-linux-extras install package

Create Linux Group

# groupadd group01 -g 500
# groupadd group02 -g 501

Create Linux User

# useradd -u 500 user01 -g 500
# useradd -u 501 user02 -g 500
# useradd -u 502 user03 -g 501


# id user01
uid=500(user01) gid=500(group01) groups=500(group01)

# id user02
uid=501(user02) gid=500(group01) groups=500(group01)

# id user03
uid=502(user03) gid=501(group02) groups=501(group02)

User Mod

# usermod user01 -aG wheel
# id user01
uid=500(user01) gid=500(group01) groups=500(group01),10(wheel)

umask

file:.bash_profile
umask 0002

$ touch tmpfile
$ ls -al
-rw-rw-r-- 1 user01 group01 0 MDAY DAY hh:mm testfile