FS_IOC_SETFLAGS(2const) - Linux manual page (original) (raw)

FSIOCSETFLAGS(2const) FSIOCSETFLAGS(2const)

NAME top

   FS_IOC_GETFLAGS, FS_IOC_SETFLAGS - ioctl() operations for inode
   flags

SYNOPSIS top

   **#include <linux/fs.h>** /* Definition of **FS_*** constants */
   **#include <sys/ioctl.h>**

   **int ioctl(int** _fd_**, FS_IOC_GETFLAGS, int ***_attr_**);**
   **int ioctl(int** _fd_**, FS_IOC_SETFLAGS, const int ***_attr_**);**

DESCRIPTION top

   Various Linux filesystems support the notion of _inode flags_—
   attributes that modify the semantics of files and directories.
   These flags can be retrieved and modified using two [ioctl(2)](../man2/ioctl.2.html)
   operations:

       int attr;
       fd = open("pathname", ...);

       ioctl(fd, FS_IOC_GETFLAGS, &attr);  /* Place current flags
                                              in 'attr' */
       attr |= FS_NOATIME_FL;              /* Tweak returned bit mask */
       ioctl(fd, FS_IOC_SETFLAGS, &attr);  /* Update flags for inode
                                              referred to by 'fd' */

   The [lsattr(1)](../man1/lsattr.1.html) and [chattr(1)](../man1/chattr.1.html) shell commands provide interfaces to
   these two operations, allowing a user to view and modify the inode
   flags associated with a file.

   The following flags are supported (shown along with the
   corresponding letter used to indicate the flag by [lsattr(1)](../man1/lsattr.1.html) and
   [chattr(1)](../man1/chattr.1.html)):

   **FS_APPEND_FL** 'a'
          The file can be opened only with the **O_APPEND** flag.  If
          applied to a directory, forbids removing files from the
          directory (via **unlink**(), **rename**(), and the like).  (This
          restriction applies even to the superuser.)  Only a
          privileged process (**CAP_LINUX_IMMUTABLE**) can set or clear
          this attribute.

   **FS_COMPR_FL** 'c'
          Store the file in a compressed format on disk.  This flag
          is _not_ supported by most of the mainstream filesystem
          implementations; one exception is **btrfs**(5).

   **FS_DIRSYNC_FL** 'D' (since Linux 2.6.0)
          Write directory changes synchronously to disk.  This flag
          provides semantics equivalent to the [mount(2)](../man2/mount.2.html) **MS_DIRSYNC**
          option, but on a per-directory basis.  This flag can be
          applied only to directories.

   **FS_IMMUTABLE_FL** 'i'
          The file is immutable: no changes are permitted to the file
          contents or metadata (permissions, timestamps, ownership,
          link count, and so on).  (This restriction applies even to
          the superuser.)  Only a privileged process
          (**CAP_LINUX_IMMUTABLE**) can set or clear this attribute.

   **FS_JOURNAL_DATA_FL** 'j'
          Enable journaling of file data on [ext3(5)](../man5/ext3.5.html) and [ext4(5)](../man5/ext4.5.html)
          filesystems.  On a filesystem that is journaling in _ordered_
          or _writeback_ mode, a privileged (**CAP_SYS_RESOURCE**) process
          can set this flag to enable journaling of data updates on a
          per-file basis.

   **FS_NOATIME_FL** 'A'
          Don't update the file last access time when the file is
          accessed.  This can provide I/O performance benefits for
          applications that do not care about the accuracy of this
          timestamp.  This flag provides functionality similar to the
          [mount(2)](../man2/mount.2.html) **MS_NOATIME** flag, but on a per-file basis.

   **FS_NOCOW_FL** 'C' (since Linux 2.6.39)
          The file will not be subject to copy-on-write updates.
          This flag has an effect only on filesystems that support
          copy-on-write semantics, such as Btrfs.  See [chattr(1)](../man1/chattr.1.html) and
          **btrfs**(5).

   **FS_NODUMP_FL** 'd'
          Don't include this file in backups made using **dump**(8).

   **FS_NOTAIL_FL** 't'
          This flag is supported only on Reiserfs.  It disables the
          Reiserfs tail-packing feature, which tries to pack small
          files (and the final fragment of larger files) into the
          same disk block as the file metadata.

   **FS_PROJINHERIT_FL** 'P' (since Linux 4.5)
          Inherit the quota project ID.  Files and subdirectories
          will inherit the project ID of the directory.  This flag
          can be applied only to directories.

   **FS_SECRM_FL** 's'
          Mark the file for secure deletion.  This feature is not
          implemented by any filesystem, since the task of securely
          erasing a file from a recording medium is surprisingly
          difficult.

   **FS_SYNC_FL** 'S'
          Make file updates synchronous.  For files, this makes all
          writes synchronous (as though all opens of the file were
          with the **O_SYNC** flag).  For directories, this has the same
          effect as the **FS_DIRSYNC_FL** flag.

   **FS_TOPDIR_FL** 'T'
          Mark a directory for special treatment under the Orlov
          block-allocation strategy.  See [chattr(1)](../man1/chattr.1.html) for details.
          This flag can be applied only to directories and has an
          effect only for ext2, ext3, and ext4.

   **FS_UNRM_FL** 'u'
          Allow the file to be undeleted if it is deleted.  This
          feature is not implemented by any filesystem, since it is
          possible to implement file-recovery mechanisms outside the
          kernel.

   In most cases, when any of the above flags is set on a directory,
   the flag is inherited by files and subdirectories created inside
   that directory.  Exceptions include **FS_TOPDIR_FL**, which is not
   inheritable, and **FS_DIRSYNC_FL**, which is inherited only by
   subdirectories.

STANDARDS top

   Linux.

NOTES top

   In order to change the inode flags of a file using the
   **FS_IOC_SETFLAGS** operation, the effective user ID of the caller
   must match the owner of the file, or the caller must have the
   **CAP_FOWNER** capability.

COLOPHON top

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Linux man-pages 6.10 2024-06-13 FSIOCSETFLAGS(2const)

Pages that refer to this page:access(2), chmod(2), chown(2), ioctl_fs(2), link(2), mount(2), setxattr(2), unlink(2), capabilities(7), xattr(7)

FS_IOC_SETFLAGS(2const) - Linux manual page (original) (raw)

NAME top

SYNOPSIS top

DESCRIPTION top

STANDARDS top

NOTES top

SEE ALSO top

COLOPHON top