扩容树莓派SD卡分区空间
每次装完树莓派上的系统，第一件事就是要把没有利用的SD卡空间利用上，因为img镜像一般都是最小化的，所以用dd还原镜像到SD卡后，SD卡都还会有一部分未使用的空间。
之前我一直都是装完系统，把SD卡笔记本上的gparted这种图形界面的软件进行扩容操作，由于现在笔记本上没有Archlinux系统了，所以这次就直接在树莓派上操作了。
[root@alarmpi ~]# fdisk /dev/mmcblk0
Welcome to fdisk (util-linux 2.25.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): p
Disk /dev/mmcblk0: 14.9 GiB, 15931539456 bytes, 31116288 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x0e8c6e83
Device Boot Start End Sectors Size Id Type
/dev/mmcblk0p1 2048 206847 204800 100M c W95 FAT32 (LBA)
/dev/mmcblk0p2 206848 2097151 1890304 923M 83 Linux
Command (m for help): d
Partition number (1,2, default 2): 2
Partition 2 has been deleted.
注意第二个分区的Start，记录下来。然后删掉第二个分区。
Command (m for help): n
Partition type
p primary (1 primary, 0 extended, 3 free)
e extended (container for logical partitions)
Select (default p): p
Partition number (2-4, default 2): 2
First sector (206848-31116287, default 206848):
Last sector, +sectors or +size{K,M,G,T,P} (206848-31116287, default 31116287):
Created a new partition 2 of type 'Linux' and of size 14.8 GiB.
Command (m for help): p
Disk /dev/mmcblk0: 14.9 GiB, 15931539456 bytes, 31116288 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x0e8c6e83
Device Boot Start End Sectors Size Id Type
/dev/mmcblk0p1 2048 206847 204800 100M c W95 FAT32 (LBA)
/dev/mmcblk0p2 206848 31116287 30909440 14.8G 83 Linux
创建个新的主分区，First sector输入第一步记录下来的那个值，也就是我这里的Default的值。新建好后，输入p查看，第二个分区的size已经调整完毕。
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Re-reading the partition table failed.: Device or resource busy
The kernel still uses the old table. The new table will be used at the next reboot or after you run partprobe(8) or kpartx(8).
[root@alarmpi ~]# reboot
输入w，保存分区表并退出，会提示分区表写入失败，因为设备正忙，直接重启即可。
[root@alarmpi ~]# resize2fs /dev/mmcblk0p2
resize2fs 1.42.12 (29-Aug-2014)
Filesystem at /dev/mmcblk0p2 is mounted on /; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/mmcblk0p2 is now 3863680 (4k) blocks long.
[root@alarmpi ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/root 15G 647M 14G 5% /
devtmpfs 214M 0 214M 0% /dev
tmpfs 218M 0 218M 0% /dev/shm
tmpfs 218M 260K 218M 1% /run
tmpfs 218M 0 218M 0% /sys/fs/cgroup
tmpfs 218M 0 218M 0% /tmp
/dev/mmcblk0p1 100M 17M 84M 17% /boot
tmpfs 44M 0 44M 0% /run/user/0
重启后，立即执行resize2fs命令，df查看容量，Avail已经是14G啦，搞定，收工。
码字不易，见好就分享~