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58 lines
2.3 KiB
Markdown
58 lines
2.3 KiB
Markdown
## Name
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mount - mount a filesystem
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## Synopsis
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```**c++
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#include <unistd.h>
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int mount(int source_fd, const char* target, const char* fs_type, int flags);
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```
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## Description
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`mount()` mounts a filesystem stored at `source_fd` by overlaying its contents
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over `target`.
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`fs_type` must be one of the following supported filesystems:
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* `Ext2FS` (or `ext2`): The ext2 filesystem.
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* `ProcFS` (or `proc`): The process pseudo-filesystem (normally mounted at `/proc`).
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* `DevPtsFS` (or `devpts`): The pseudoterminal pseudo-filesystem (normally mounted at `/dev/pts`).
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* `TmpFS` (or `tmp`): A non-persistent filesystem that stores all its data in RAM. An instance of this filesystem is normally mounted at `/tmp`.
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For Ext2FS, `source_fd` must refer to an open file descriptor to a file containing
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the filesystem image. This may be a device file or any other seekable file. All
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the other filesystems ignore the `source_fd` — you can even pass an invalid file
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descriptor such as -1.
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The following `flags` are supported:
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* `MS_NODEV`: Disallow opening any devices from this file system.
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* `MS_NOEXEC`: Disallow executing any executables from this file system.
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* `MS_NOSUID`: Ignore set-user-id bits on executables from this file system.
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* `MS_BIND`: Perform a bind-mount (see below).
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These flags can be used as a security measure to limit the possible abuses of the newly
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mounted file system.
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### Bind mounts
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If `MS_BIND` is specified in `flags`, `fs_type` is ignored and a bind mount is
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performed instead. In this case, the file or directory specified by `source_fd`
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is overlayed over `target` — the target appears to be replaced by a copy of the
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source. This can be used as an alternative to symlinks or hardlinks.
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## Errors
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* `EFAULT`: The `fs_type` or `target` are invalid strings.
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* `EPERM`: The current process does not have superuser privileges.
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* `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.
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* `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.
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All of the usual path resolution errors may also occur.
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## See also
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* [`mount`(8)](../man8/mount.md)
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