初始化状态后

[root@bandwagon ~]# free -lh
             total       used       free     shared    buffers     cached
Mem:          507M        66M       441M       148K       5.8M        29M
Low:          507M        66M       441M
High:           0B         0B         0B
-/+ buffers/cache:        31M       476M
Swap:         131M         0B       131M

[root@bandwagon ~]# df -lh
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2        11G  855M  9.1G   9% /
tmpfs           254M     0  254M   0% /dev/shm
/dev/sda1       283M   55M  214M  21% /boot


[root@bandwagon ~]# cat /etc/centos-release
CentOS release 6.8 (Final)

[root@bandwagon ~]# uname -a
Linux bandwagon 4.10.4-1.el6.elrepo.i686 #1 SMP Sat Mar 18 11:05:18 EDT 2017 i68
6 i686 i386 GNU/Linux

[root@bandwagon ~]# cat /etc/centos-release
CentOS Linux release 7.3.1611 (Core)

[root@bandwagon ~]# free -lh
              total        used        free      shared  buff/cache   available
Mem:           503M         58M         69M        8.3M        376M        413M
Low:           503M        434M         69M
High:            0B          0B          0B
Swap:          131M          0B        131M

[root@bandwagon ~]# df -lh
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        242M     0  242M   0% /dev
tmpfs           252M     0  252M   0% /dev/shm
tmpfs           252M  8.3M  244M   4% /run
tmpfs           252M     0  252M   0% /sys/fs/cgroup
/dev/sda2 11G 1.3G 8.6G 13% /
/dev/sda1       380M  142M  218M  40% /boot
tmpfs            51M     0   51M   0% /run/user/0
[root@bandwagon ~]#

安装centos6 比 centos7 节省空间和资源，但是centos7更方便安装，最后还是选择 centos7。