On Fri, 04 Mar 2016 08:11:43 +0100 Frédéric Marchal <frederic.marc...@wowtechnology.com> wrote:
> On Friday 04 March 2016 07:18:59 Adam Wilson wrote: > > On Fri, 4 Mar 2016 04:03:01 +1100 Andrew McGlashan > > > > <andrew.mcglas...@affinityvision.com.au> wrote: > > > On 4/03/2016 3:07 AM, Adam Wilson wrote: > > > > On Fri, 4 Mar 2016 03:03:53 +1100 Andrew McGlashan > > > > > > > > <andrew.mcglas...@affinityvision.com.au> wrote: > > > >> It also may have been files in the file system, but where > > > >> another file system mount hides them.... > > > > > > > > What does this mean? Mounts overlapping and hiding other mounts? > > > > > > > > Explain, please. > > > > > > Yes, this is more likely to happen to the root file system. > > > > > > Say you have a bunch of files in /boot, but for some reason you > > > have a /boot partition that wasn't mounted when those files were > > > created .... then you mount the /normal/ boot partition over it > > > and now the other files are now hidden from view, but still > > > taking up space. > > > > So you're talking about creating files in an unmounted partition, > > and then mounting it, but since file addition happened when the FS > > was still in an unmounted state, the new files weren't written to > > the journal? > > > > Surely in that case the new files would simply not be registered and > > act as free space (as if they had been deleted)? > > This is not about a caching service. It is about the way the content > of a mounted disk is made visible to you. > > Have you ever wondered how a path name, on your main hard disk, such > as /mnt/usb becomes a link to a USB disk known to the system > as /dev/sdd1? > > When you type > > mount /dev/sdd1 /mnt/usb > > It tells the system that, from now on, the directory named "/mnt/usb" > becomes the entry point to the file system that sit at "/dev/sdd1". > > Any call such as "ls /mnt/usb" will list the content of the USB disk > instead of the usual content of /mnt/usb. > > When the device is unmounted, the directory that serves as its mount > point is restored as a regular directory. > > Now, imagine /mnt/usb is not mounted. It is a directory just like any > other. If you copy files to /mnt/usb, they will be copied to that > directory and you have access to them as long as no device is mounted > under /mnt/usb. Ah. I see. Thank you for that- I was a little bit unsure as to what was being referred to, until you came and gave an example.
