Ext4

ext4 journaling file system or fourth extended filesystem is a journaling file system for Linux and it is the default file system for many Linux distributions such as Ubuntu and Debian. RHEL default fs is XFS.

Since Linux kernel 4.1 on June 2015, ext4 natively supports file encryption

Basic commands

• mkfs and mke2fs
• Creating an ext4 filesystem: (by default since 2010 will do a quick and lazy initialization )

Creating an ext4 in a disk

mkfs.ext4 /dev/sdX

Creating an ext4 FS in an LV:

mkfs.ext4 /dev/vg01/lv01

To prevent lazy initialization mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/mapper/fc-root

• resize2fs (See also: xfs_growfs)

resize2fs

resize2fs file system resizer for ext2/ext3/ext4 (resize2fs /dev/mapper/VolGroup-lv_root). Online resize (expand) is supported in resize2fs since 2006.. resize2fs code: https://github.com/tytso/e2fsprogs/blob/master/resize/resize2fs.c. See also: ext2online

EXT4 Features timeline

• 2015 File encryption
• 2010 Lazy Initialization
• 2006 Online resize (expand) support

Activities

Basic

1. Create an file ext4 system using: mkfs.ext4
2. Create an ext4 file system an mount it using systemd: https://codingbee.net/rhcsa/rhcsa-mount-filesystems-during-boot-time-using-systemd

Advanced

1. Configure an LVM Volume with an ext4 filesystem: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/high_availability_add-on_administration/s1-lvmsetupnfs-haaa
2. Learn about Lazy initialization feature of ext4: https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem#Lazy_Initialization

See also

• ZFS, LVM (lvcreate), mdadm, fdisk and partitions
• XFS default filesystem for RHEL 7.0 in 2014.
• tune2fs which allows among other actions to modify reserved space
• ext2online
• JFS2, mkfs.jfs (Linux), jfsutils and xfs_growfs
• chfs (AIX)
• inode, superblock and block size
• stat command. stat -c %h -- YOUR_FILE
• mount and findmnt
• fsck and e2fsck
• ext4 e2fsck, fsck.ext4, superblock, inode, block size, mkfs.ext4 tune2fs, wipefs, resize2fs stat, extents, Review ext4 journalctl logs. Read-only file system, virt-resize, ACL
• chmod, setuid and setgid
• wipefs

https://lwn.net/Articles/639427/

https://en.wikipedia.org/wiki/Ext4#Features

https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem#Lazy_Initialization

https://manpages.debian.org/stretch/e2fsprogs/resize2fs.8.en.html

https://github.com/tytso/e2fsprogs/commit/bf69235ad0073c80386b70caba0e1b58e5f85697

https://www.technomenace.com/2014/08/how-to-extend-lvm-on-qcow2-images/

https://en.wikipedia.org/wiki/Ext4#Features

https://help.ubuntu.com/community/InstallingANewHardDrive

https://linux.die.net/man/8/xfs_growfs

https://unix.stackexchange.com/questions/167610/determining-if-a-file-is-a-hard-link-or-symbolic-link