fork from here http://www.cnblogs.com/hugetong/p/6914248.html
boot分区，MBR加密：https://wiki.archlinux.org/index.php/Dm-crypt/Specialties#Securing_the_unencrypted_boot_partition
首先，我选择在LUKS上创建btrfs。查看上述文档的btrfs章节。
1. btrfs不支持swap file，必须使用swap分区 https://wiki.archlinux.org/index.php/Btrfs#Swap_file
2. 不建议在裸盘直接使用btrfs文件系统。https://wiki.archlinux.org/index.php/Btrfs#Partitionless_Btrfs_disk
3. btrfs带压缩会提高性能表现。https://wiki.archlinux.org/index.php/Btrfs#Compression
4. 新概念 subvolumes。 https://wiki.archlinux.org/index.php/Btrfs#Subvolumes
这个更详细，讲的更清楚，上边那个讲的很不清楚。。。：https://btrfs.wiki.kernel.org/index.php/SysadminGuide#Subvolumes
btrfs文档：https://wiki.archlinux.org/index.php/Btrfs （跟上边那一堆，明明都是一个。。。）
多个磁盘的情况下可以组成一个pool，Btrfs支持 RAID0，1, 10, 5, 6。https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices
5. 不要使用btrfs 的 RAID5, RAID6模式。
6. 常用命令们
https://btrfs.wiki.kernel.org/index.php/Getting_started#Basic_Filesystem_Commands
7. 最大容量 70% ？？
Be aware that for that size, it will report full when reaching about 75%.
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1. 初始化一个 btrfs 文件系统
1 root@archiso ~ # mkfs.btrfs -L vd_root -f /dev/mapper/vd_root :( btrfs-progs v4.10.2 See http://btrfs.wiki.kernel.org for more information. Label: vd_root UUID: ba0b8b0b-8753-455b-90f6-422f61d59df1 Node size: 16384 Sector size: 4096 Filesystem size: 20.00GiB Block group profiles: Data: single 8.00MiB Metadata: DUP 1.00GiB System: DUP 8.00MiB SSD detected: no Incompat features: extref, skinny-metadata Number of devices: 1 Devices: ID SIZE PATH 1 20.00GiB /dev/mapper/vd_root root@archiso ~ #
2. 创建一个 subvolume
root@archiso ~ # btrfs subvolume create mnt/real_root Create subvolume 'mnt/real_root'
3. 创建快照（很显然从命令来看，快照也是一个subvolume ）
root@archiso ~ # btrfs subvolume snapshot mnt/real_root mnt/snapshot_of_real_root Create a snapshot of 'mnt/real_root' in 'mnt/snapshot_of_real_root'
4. 设置default
root@archiso ~ # btrfs subvolume set-default 257 mnt root@archiso ~ # btrfs subvolume get-default mnt ID 257 gen 16 top level 5 path real_root
5. 删除快照或subvolume
root@archiso ~ # btrfs subvolume list /root/mnt ID 257 gen 22 top level 5 path real_root ID 258 gen 16 top level 5 path snapshot_of_real_root ID 259 gen 22 top level 5 path snapshot/snapshot_of_real_root_2 root@archiso ~ # btrfs subvolume create mnt/test Create subvolume 'mnt/test' root@archiso ~ # btrfs subvolume list /root/mnt ID 257 gen 22 top level 5 path real_root ID 258 gen 16 top level 5 path snapshot_of_real_root ID 259 gen 22 top level 5 path snapshot/snapshot_of_real_root_2 ID 260 gen 24 top level 5 path test root@archiso ~ # btrfs subvolume delete mnt/test Delete subvolume (no-commit): '/root/mnt/test' root@archiso ~ # btrfs subvolume list /root/mnt ID 257 gen 22 top level 5 path real_root ID 258 gen 16 top level 5 path snapshot_of_real_root ID 259 gen 22 top level 5 path snapshot/snapshot_of_real_root_2 root@archiso ~ #
6. 根据文档里的描述， 选用Flat方式创建subvolume
https://btrfs.wiki.kernel.org/index.php/SysadminGuide#Flat
root@archiso ~ # find mnt mnt mnt/real_root mnt/real_root/root mnt/real_root/home mnt/snapshot root@archiso ~ # btrfs subvolume get-default mnt ID 257 gen 30 top level 5 path real_root root@archiso ~ # btrfs subvolume list mnt ID 257 gen 30 top level 5 path real_root ID 261 gen 29 top level 257 path real_root/root ID 262 gen 30 top level 257 path real_root/home root@archiso ~ #
7. 挂载指定的 subvolume
root@archiso ~ # btrfs subvolume list mnt ID 257 gen 12 top level 5 path top ID 258 gen 11 top level 257 path top/root ID 259 gen 12 top level 257 path top/home root@archiso ~ # mount -o subvol=top/root /dev/mapper/crypt_root mnt