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20th chunk of `mount.man`
1cece2c79b6035aed6f0fe0ce3124bc81a0df1b11cb654df0000000100000fa2
  Sets the mode of the mountpoint.

   Mount options for devpts
       The devpts filesystem is a pseudo filesystem, traditionally mounted on
       /dev/pts. In order to acquire a pseudo terminal, a process opens
       /dev/ptmx; the number of the pseudo terminal is then made available to
       the process and the pseudo terminal slave can be accessed as
       /dev/pts/<number>.

       uid=value and gid=value
           This sets the owner or the group of newly created pseudo terminals
           to the specified values. When nothing is specified, they will be set
           to the UID and GID of the creating process. For example, if there is
           a tty group with GID 5, then gid=5 will cause newly created pseudo
           terminals to belong to the tty group.

       mode=value
           Set the mode of newly created pseudo terminals to the specified
           value. The default is 0600. A value of mode=620 and gid=5 makes
           "mesg y" the default on newly created pseudo terminals.

       newinstance
           Create a private instance of the devpts filesystem, such that
           indices of pseudo terminals allocated in this new instance are
           independent of indices created in other instances of devpts.

           All mounts of devpts without this newinstance option share the same
           set of pseudo terminal indices (i.e., legacy mode). Each mount of
           devpts with the newinstance option has a private set of pseudo
           terminal indices.

           This option is mainly used to support containers in the Linux
           kernel. It is implemented in Linux kernel versions starting with
           2.6.29. Further, this mount option is valid only if
           CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
           configuration.

           To use this option effectively, /dev/ptmx must be a symbolic link to
           pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux
           kernel source tree for details.

       ptmxmode=value
           Set the mode for the new ptmx device node in the devpts filesystem.

           With the support for multiple instances of devpts (see newinstance
           option above), each instance has a private ptmx node in the root of
           the devpts filesystem (typically /dev/pts/ptmx).

           For compatibility with older versions of the kernel, the default
           mode of the new ptmx node is 0000. ptmxmode=value specifies a more
           useful mode for the ptmx node and is highly recommended when the
           newinstance option is specified.

           This option is only implemented in Linux kernel versions starting
           with 2.6.29. Further, this option is valid only if
           CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
           configuration.

   Mount options for fat
       (Note: fat is not a separate filesystem, but a common part of the msdos,
       umsdos and vfat filesystems.)

       blocksize={512|1024|2048}
           Set blocksize (default 512). This option is obsolete.

       uid=value and gid=value
           Set the owner and group of all files. (Default: the UID and GID of
           the current process.)

       umask=value
           Set the umask (the bitmask of the permissions that are not present).
           The default is the umask of the current process. The value is given
           in octal.

       dmask=value
           Set the umask applied to directories only. The default is the umask
           of the current process. The value is given in octal.

       fmask=value
           Set the umask applied to regular files only. The default is the
           umask of the current process. The value is given in octal.

       allow_utime=value
           This option controls the permission check of mtime/atime.

           20
               If current process is in group of file’s group ID, you can
               change timestamp.

           2
Title: Filesystem-Specific Mount Options: devpts and fat
Summary
The document details mount options specific to devpts and fat filesystems. For devpts, it describes `uid`, `gid`, and `mode` to configure ownership and permissions of newly created pseudo terminals, `newinstance` for creating a private instance, and `ptmxmode` for setting the mode of the ptmx device node. For fat, it lists `blocksize`, `uid`, `gid`, `umask`, `dmask`, `fmask`, and `allow_utime` to control block size, ownership, permissions, and timestamp modification permissions.