Filesystem limitations

POSIX defines the set of services a filesystem must provide. However, not all filesystems are capable of delivering all those services.

Filesystem Access date Modification date Status change date Filename lengtha Permissions Directories Hard links Soft links Decompression on read
Image No No No 255 Yes No No No No
RAMb Yes Yes Yes 255 Yes No No No No
ETFS Yes Yes Yes 91 Yes Yes No Yes No
QNX 4 Yes Yes Yes 48c Yes Yes Yes Yes No
Power-Safe Yes Yes Yes 510 Yes Yes Yes Yes No
DOS Yesd Yes No 8.3e No Yes No No No
NTFS Yes Yes Yes 755 No Yes No No Yes
CD-ROM Yesf Yesf Yesf 207g Yesf Yes No Yesf No
UDF Yes Yes Yes 254 Yes Yes No No No
HFS, HFS Plus Yes Yes Yes 255h Yes Yes Yes Yes No
FFS3 No Yes Yes 255 Yes Yes No Yes No
NFS Yes Yes Yes i Yesi Yes Yesi Yesi No
CIFS No Yes No i Yesi Yes No No No
Ext2 Yes Yes Yes 255 Yes Yes Yes Yes No

a Our internal representation for file names is UTF-8, which uses a variable number of bytes per character. Many on-disk formats instead use UCS2, which is a fixed number (2 bytes). Thus a length limit in characters may be 1, 2, or 3 times that number in bytes, as we convert from on-disk to OS representation. The lengths for the QNX 4, Power-Safe, and EXT2 filesystems are in bytes; those for UDF, CD/Joliet, and DOS/VFAT are in characters.

b The RAM "filesystem" (/dev/shmem) isn't really a filesystem; it's a window onto the shared memory names that has some filesystem-like characteristics. See "Builtin RAM disk" later in this chapter.

c 505 if .longfilenames is enabled; otherwise, 48.

d VFAT or FAT32 (Windows 95 or later).

e 255-character filename lengths used by VFAT or FAT32 (Windows 95 or later).

f With Rock Ridge extensions.

g 103 characters with Joliet extensions; 255 with Rock Ridge extensions.

h 31 on HFS.

i Limited by the remote filesystem.