Do Empty Files Consume Disk Space? Understanding Inodes in Linux

We start by questioning if creating an empty file with touch on Linux actually consumes disk space and aim to provide a clear answer by examining the Linux file system principles.

Using touch empty_file.txt and ls -l, the file size appears as 0, but the intuition suggests some space must be used.

# touch abcdefghigklmn.txt
# ls -l
total 0
-rw-r--r-- 1 root root 0 Aug 17 17:49 empty.file

Running df -i shows inode usage; after creating another empty file the IUsed count increases by one, confirming that a new inode is allocated.

# df -i
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
......
/dev/sdb1            2147361984 12785019 2134576965   1% /search

# touch empty_file2.txt
df -i
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
......
/dev/sdb1            2147361984 12785020 2134576964   1% /search

The conclusion is that creating an empty file consumes one inode.

To understand what an inode stores, we look at the ext2_inode structure from the Linux source (fs/ext2/ext2.h):

struct ext2_inode {
    __le16  i_mode;          # file permissions
    __le16  i_uid;           # owner UID
    __le32  i_size;          # file size in bytes
    __le32  i_atime;         # last access time
    __le32  i_ctime;         # creation time
    __le32  i_mtime;         # modification time
    __le32  i_dtime;         # deletion time
    __le16  i_gid;           # group ID
    __le16  i_links_count;   # link count
    __le32  i_blocks;        # block count
    ...
    __le32  i_block[EXT2_N_BLOCKS]; # block pointers
    ...
};

Using stat we can view an inode's metadata directly:

# stat test
  File: `test'
  Size: 0          Blocks: 0   IO Block: 1024 regular empty file
Device: 801h/2049d  Inode: 26   Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2020-03-01 12:14:31.000000000 +0800
Modify: 2020-03-01 12:14:31.000000000 +0800
Change: 2020-03-01 12:14:31.000000000 +0800

Each inode occupies a fixed size; on the author’s machine it is 256 bytes, as shown by dumpe2fs -h:

# dumpe2fs -h /dev/mapper/vgroot-lvroot
dumpe2fs 1.41.12 (17-May-2010)
...
Inode size:               256

Interestingly, the inode itself does not store the file name. File names are kept in the directory’s data structures. The relevant ext2_dir_entry struct is:

struct ext2_dir_entry {
    __le32  inode;          /* Inode number */
    __le16  rec_len;        /* Directory entry length */
    __le16  name_len;       /* Name length */
    char    name[];         /* File name, up to EXT2_NAME_LEN */
};

Thus, creating an empty file consumes one inode and also a small amount of space in the parent directory’s block to store the name and inode number.

The article ends with a real‑world incident where a machine ran out of inodes because a process kept creating empty log files, leading to service failure until the unnecessary files were removed.