Unionfs: 联合文件系统.Unionfs是一个堆栈式的联合文件系统, 2004年由纽约州立大学石溪分校开发, 它可以把多个目录(也叫分支)内容合并在一起, 而目录的物理位置是分开的. Unionfs允许只读和可读写目录并存,就是说可同时删除和增加内容. Unionfs应用的地方很多, 比如在多个磁盘分区上合并不同文件系统的主目录,或把几张CD光盘合并成一个统一的光盘目录(归档). 另外,具有写时复制(copy-on-write)功能Unionfs可以把只读和可读写文件系统合并在一起,虚拟上允许只读文件系统的修改可以保存到可写文件系统当中.
Unionfs, developed at Stony Brook university since 2004, is a stackable unification file system, which can merge the contents of several directories (so called branches) while keeping their physical content separate. It allows any mix of read-only and read-write branches, as well as insertion and deletion of branches on the fly. Unionfs can be used in several ways, for example to unify home directories from multiple filesystems on different disk partitions, or to merge several CDs to create a unified view of a photo archive. In a similar view, Unionfs, with copy-on-write functionality, can be used to merge read-only and read-write filesystems together and to virtually allow modification of read-only filesystems saving changes to the writable ones.
SLAX is a 177 MB Linux Live distribution which aims at compacting full featured Linux operating system to a portable medium (like usb flash drive or mini-cd) and allows everyone to boot Linux on any machine without the need to install it. It works even on computers with no harddisk at all. Unionfs is the most important part of a SLAX, it allows SLAX to seem and act as a real Linux OS with full-writable root directory tree. So let s speak about unionfs first.