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Kernel & Userland: Allow to mount image files formatted with Ext2FS

This commit is contained in:
Liav A 2020-03-26 02:51:16 +02:00 committed by Andreas Kling
parent 6b59311d4b
commit a60ea79a41
8 changed files with 101 additions and 51 deletions

View file

@ -7,12 +7,13 @@ mount - mount a filesystem
```**c++
#include <unistd.h>
int mount(const char* source, const char* target, const char* fs_type, int flags);
int mount(int source_fd, const char* target, const char* fs_type, int flags);
```
## Description
`mount()` mounts a filesystem stored at `source` by overlaying its contents over `target`.
`mount()` mounts a filesystem stored at `source_fd` by overlaying its contents
over `target`.
`fs_type` must be one of the following supported filesystems:
@ -21,9 +22,10 @@ int mount(const char* source, const char* target, const char* fs_type, int flags
* `DevPtsFS` (or `devpts`): The pseudoterminal pseudo-filesystem (normally mounted at `/dev/pts`).
* `TmpFS` (or `tmp`): A non-persistent filesystem that stores all its data in RAM. An instance of this filesystem is normally mounted at `/tmp`.
For Ext2FS, `source` must be a path to a block device storing the filesystem contents. All
the other filesystems ignore the `source` argument (by convention, it should have the same
value as `fs_type`).
For Ext2FS, `source_fd` must refer to an open file descriptor to a file containing
the filesystem image. This may be a device file or any other seekable file. All
the other filesystems ignore the `source_fd` — you can even pass an invalid file
descriptor such as -1.
The following `flags` are supported:
@ -37,14 +39,22 @@ mounted file system.
### Bind mounts
If `MS_BIND` is specified in `flags`, `fs_type` is ignored and a bind mount is performed
instead. In this case `source` is treated as a path to a file or directory whose contents
are overlayed over `target`. This can be used as an alternative to symlinks or hardlinks.
If `MS_BIND` is specified in `flags`, `fs_type` is ignored and a bind mount is
performed instead. In this case, the file or directory specified by `source_fd`
is overlayed over `target` — the target appears to be replaced by a copy of the
source. This can be used as an alternative to symlinks or hardlinks.
## Errors
* `EFAULT`: The `fs_type` or `target` are invalid strings.
* `EPERM`: The current process does not have superuser privileges.
* `ENODEV`: The `fs_type` is unrecognized, or the device is not found, or the device doesn't contain a valid filesystem image.
* `ENODEV`: The `fs_type` is unrecognized, or the file descriptor to source is
not found, or the source doesn't contain a valid filesystem image. Also, this
error occurs if `fs_type` is valid, but the file descriptor from `source_fd`
is not seekable.
* `EBADF`: If the `source_fd` is not valid, and either `fs_type` specifies a
file-backed filesystem (and not a pseudo filesystem), or `MS_BIND` is
specified in flags.
All of the usual path resolution errors may also occur.

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@ -12,18 +12,26 @@ $ mount
## Description
If invoked without any arguments, `mount` prints a list of all currently mounted filesystems.
If invoked without any arguments, `mount` prints a list of all currently mounted
filesystems.
If invoked as `mount -a`, `mount` mounts all the filesystems configured in `/etc/fstab`. This
is normally done on system startup by [`SystemServer`(7)](../man7/SystemServer.md).
If invoked as `mount -a`, `mount` mounts all the filesystems configured in
`/etc/fstab`. This is normally done on system startup by
[`SystemServer`(7)](../man7/SystemServer.md).
Otherwise, `mount` performs a single filesystem mount. Source, target, and fstype have the
same meaning as in the [`mount`(2)](../man2/mount.md) syscall (if not specified, fstype
defaults to `ext2`).
Otherwise, `mount` performs a single filesystem mount. Source should be a path
to a file containing the filesystem image. Target, and fstype have the same
meaning as in the [`mount`(2)](../man2/mount.md) syscall (if not specified,
fstype defaults to `ext2`).
Options correspond to the mount flags, and should be specified as a comma-separated list of
flag names (lowercase and without the `MS_` prefix). Additionally, the name `defaults` is
accepted and ignored.
A special source value "none" is recognized, in which case
[`mount`(8)](mount.md) will not attempt to open the source as a file, and will
pass an invalid file descriptor to [`mount`(2)](../man2/mount.md). This is
useful for mounting pseudo filesystems.
Options correspond to the mount flags, and should be specified as a
comma-separated list of flag names (lowercase and without the `MS_` prefix).
Additionally, the name `defaults` is accepted and ignored.
## Files