| A | B |
|---|---|
| Developer(s) | Mingming Cao, Andreas Dilger, Alex Zhuravlev (Tomas), Dave Kleikamp, Theodore Ts’o, Eric Sandeen, Sam Naghshineh, others |
| Full name | Fourth extended file system |
| Introduced | 10 October 2006 with Linux 2.6.19 |
| Preceded by | ext3 |
| Partition IDs | 0x83: MBR / EBR. EBD0A0A2-B9E5-4433-87C0-68B6B72699C7: GPT Windows BDP.1 0FC63DAF-8483-4772-8E79-3D69D8477DE4: GPT Linux filesystem data.1 933AC7E1-2EB4-4F13-B844-0E14E2AEF915: GPT /home partition.2 3B8F8425-20E0-4F3B-907F-1A25A76F98E8: GPT /srv (server data) partition. |
| Structures | … |
| Directory contents | Linked list, hashed B-tree |
| File allocation | Extents / Bitmap |
| Bad blocks | Table |
| Limits | … |
| Max volume size | 1 EiB |
| Max file size | 16–256 TiB (for 4–64 KiB block size) |
| Max no. of files | 4 billion (specified at filesystem creation time) |
| Max filename length | 255 bytes (fewer for multibyte character encodings such as Unicode) |
| Allowed filename characters | All characters and character sequences permitted, except for NULL (‘\0’), ’/’, and the special file names ”.” and ”..” which are reserved for indicating (respectively) current and parent directories. |
| Features | … |
| Dates recorded | Modification (mtime), data or attribute modification (ctime), access (atime), deletion (dtime), creation (crtime) |
| Date range | 14 December 1901 – 10 May 24463 |
| Date resolution | Nanosecond |
| Forks | No |
| Attributes | acl, bh, bsddf, commit=nrsec, data=journal, data=ordered, data=writeback, delalloc, extents, journal_dev, mballoc, minixdf, noacl, nobh, nodelalloc, noextents, nomballoc, nombcache, nouser_xattr, oldalloc, orlov, user_xattr |
| File system permissions | Unix permissions, POSIX ACLs |
| Transparent compression | No |
| Transparent encryption | Yes |
| Data deduplication | No |
| Copy-on-write | No |
| Other | … |
| Supported operating systems | • Linux • FreeBSD (full read/write support since version 12.0) • macOS (read-only with ext4fuse, full with ExtFS) • Windows (read–write without journaling with ext2fsd) • KolibriOS (read-only) |
ext4
(echo:: @ ᯤ)
Footnotes
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Previously, Linux used the same GUID for the data partitions as Windows (Basic data partition: EBD0A0A2- B9E5- 4433- 87C0- 68B6B72699C7). Linux never had a separate unique partition type GUID defined for its data partitions. This created problems when dual-booting Linux and Windows in UEFI-GPT setup. The new GUID (Linux filesystem data: 0FC63DAF- 8483- 4772- 8E79- 3D69D8477DE4) was defined jointly by GPT fdisk and GNU Parted developers. It is identified as type code 0x8300 in GPT fdisk. (See definitions in gdisk’s parttypes.cc) ↩ ↩2
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“DiscoverablePartitionsSpec”. freedesktop.org. Retrieved 7 April 2018. ↩
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“ext4: Fix handling of extended tv_sec”. Linux-stable kernel tree. Retrieved 14 February 2017. ↩