--- name: "mknod" section: "2" platform: "linux" package: "man-pages" version: "6.19-1" release: "Arch Linux 2026-11-01" platforms: ["linux", "freebsd", "macos"] url: "https://new.carta.tech/mknod/2" --- # mknod(2) create a special or ordinary file ## NAME mknod, mknodat - create a special or ordinary file ## LIBRARY Standard C library (*libc*, *-lc*) ## SYNOPSIS ``` #include ``` **int mknod(const char \****path***, mode\_t** *mode***, dev\_t** *dev***);** **#include \** /\* Definition of AT\_\* constants \*/ **#include \** **int mknodat(int** *dirfd***, const char \****path***, mode\_t** *mode***, dev\_t** *dev***);** Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)): **mknod**(): ``` _XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE ``` ## DESCRIPTION The system call **mknod**() creates a filesystem node (file, device special file, or named pipe) named *path*, with attributes specified by *mode* and *dev*. The *mode* argument specifies both the file mode to use and the type of node to be created. It should be a combination (using bitwise OR) of one of the file types listed below and zero or more of the file mode bits listed in [**inode**(7)](/inode/7.md). The file mode is modified by the process's *umask* in the usual way: in the absence of a default ACL, the permissions of the created node are (*mode* & ~*umask*). The file type must be one of **S\_IFREG**, **S\_IFCHR**, **S\_IFBLK**, **S\_IFIFO**, or **S\_IFSOCK** to specify a regular file (which will be created empty), character special file, block special file, FIFO (named pipe), or UNIX domain socket, respectively. (Zero file type is equivalent to type **S\_IFREG**.) If the file type is **S\_IFCHR** or **S\_IFBLK**, then *dev* specifies the major and minor numbers of the newly created device special file ([**makedev**(3)](/makedev/3.md) may be useful to build the value for *dev*); otherwise it is ignored. If *path* already exists, or is a symbolic link, this call fails with an **EEXIST** error. The newly created node will be owned by the effective user ID of the process. If the directory containing the node has the set-group-ID bit set, or if the filesystem is mounted with BSD group semantics, the new node will inherit the group ownership from its parent directory; otherwise it will be owned by the effective group ID of the process. ### mknodat() The **mknodat**() system call operates in exactly the same way as **mknod**(), except for the differences described here. If *path* is relative, then it is interpreted relative to the directory referred to by the file descriptor *dirfd* (rather than relative to the current working directory of the calling process, as is done by **mknod**() for a relative pathname). If *path* is relative and *dirfd* is the special value **AT\_FDCWD**, then *path* is interpreted relative to the current working directory of the calling process (like **mknod**()). If *path* is absolute, then *dirfd* is ignored. See [**openat**(2)](/openat/2.md) for an explanation of the need for **mknodat**(). ## RETURN VALUE **mknod**() and **mknodat**() return zero on success. On error, -1 is returned and *errno* is set to indicate the error. ## ERRORS - **EACCES** The parent directory does not allow write permission to the process, or one of the directories in the path prefix of *path* did not allow search permission. (See also [**path\_resolution**(7)](/path_resolution/7.md).) - **EBADF** (**mknodat**()) *path* is relative but *dirfd* is neither **AT\_FDCWD** nor a valid file descriptor. - **EDQUOT** The user's quota of disk blocks or inodes on the filesystem has been exhausted. - **EEXIST** *path* already exists. This includes the case where *path* is a symbolic link, dangling or not. - **EFAULT** *path* points outside your accessible address space. - **EINVAL** *mode* requested creation of something other than a regular file, device special file, FIFO or socket. - **ELOOP** Too many symbolic links were encountered in resolving *path*. - **ENAMETOOLONG** *path* was too long. - **ENOENT** A directory component in *path* does not exist or is a dangling symbolic link. - **ENOMEM** Insufficient kernel memory was available. - **ENOSPC** The device containing *path* has no room for the new node. - **ENOTDIR** A component used as a directory in *path* is not, in fact, a directory. - **ENOTDIR** (**mknodat**()) *path* is relative and *dirfd* is a file descriptor referring to a file other than a directory. - **EPERM** *mode* requested creation of something other than a regular file, FIFO (named pipe), or UNIX domain socket, and the caller is not privileged (Linux: does not have the **CAP\_MKNOD** capability); also returned if the filesystem containing *path* does not support the type of node requested. - **EROFS** *path* refers to a file on a read-only filesystem. ## VERSIONS POSIX.1-2001 says: "The only portable use of **mknod**() is to create a FIFO-special file. If *mode* is not **S\_IFIFO** or *dev* is not 0, the behavior of **mknod**() is unspecified." However, nowadays one should never use **mknod**() for this purpose; one should use [**mkfifo**(3)](/mkfifo/3.md), a function especially defined for this purpose. Under Linux, **mknod**() cannot be used to create directories. One should make directories with [**mkdir**(2)](/mkdir/2.md). ## STANDARDS POSIX.1-2024 XSI. ## HISTORY - **mknod**() SVr4, 4.4BSD, SUSv1, POSIX.1-2001 XSI (but see VERSIONS). - **mknodat**() glibc 2.4, Linux 2.6.16, POSIX.1-2008 XSI. ## NOTES There are many infelicities in the protocol underlying NFS. Some of these affect **mknod**() and **mknodat**(). ## SEE ALSO [**mknod**(1)](/mknod/1.md), [**chmod**(2)](/chmod/2.md), [**chown**(2)](/chown/2.md), [**fcntl**(2)](/fcntl/2.md), [**mkdir**(2)](/mkdir/2.md), [**mount**(2)](/mount/2.md), [**socket**(2)](/socket/2.md), [**stat**(2)](/stat/2.md), [**umask**(2)](/umask/2.md), [**unlink**(2)](/unlink/2.md), [**makedev**(3)](/makedev/3.md), [**mkfifo**(3)](/mkfifo/3.md), [**acl**(5)](/acl/5.md), [**path\_resolution**(7)](/path_resolution/7.md)