1. RANDOM

    例：echo $RANDOM

  2. openssl rand -base64 8

  3. 用时间

    date +%s%N

    date +%t%N

  4. head /dev/urandom/cksum

  5. 利用UUID

  6. expect

    yum install expect -y

    mkpasswd -l 8

一般可以用如下取随机

echo $(date +%t%N)$RANDOM |md5sum

测试随机性

for n in `seq 20`

do

  echo $RANDOM|md5sum|cut -c 1-9

done > a.txt

sort

uniq -c

sort -rn -k1