Editing Ext4

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[[wikipedia:ext4|ext4]] ([[2008]]) [[journaling]] [[File system|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]]. [[Red Hat Enterprise Linux|RHEL]] default fs is [[XFS]].

Since [[Linux kernel]] [[4.1]] on June 2015<ref>https://lwn.net/Articles/639427/</ref>, ext4 natively supports file [[cryptography|encryption]]

* https://man7.org/linux/man-pages/man5/ext4.5.html

==Basic commands==
*[[mkfs]] and [[mke2fs]]
* Creating an ext4 filesystem: (by default since 2010 will do a quick and lazy initialization <ref>https://en.wikipedia.org/wiki/Ext4#Features</ref>)
:Creating an ext4 in a disk
:: <code>[[mkfs.ext4]] [[/dev/sd]]X</code> 
:Creating an ext4 FS in an [[Linux Administration/Devices and Filesystems/LVM|LV]]:
:: <code>mkfs.ext4 /dev/vg01/lv01</code> 
:To prevent lazy initialization <code>mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/mapper/fc-root</code><ref>https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem#Lazy_Initialization</ref>
* [[resize2fs]] (See also: [[xfs_growfs]])

=== resize2fs ===
<code>[[resize2fs]]</code><ref>https://manpages.debian.org/stretch/e2fsprogs/resize2fs.8.en.html</ref> file system resizer  for ext2/ext3/[[ext4]] (<code>resize2fs /dev/mapper/VolGroup-lv_root</code>). Online resize (expand) is supported in resize2fs since 2006<ref>https://github.com/tytso/e2fsprogs/commit/bf69235ad0073c80386b70caba0e1b58e5f85697</ref>.<ref>https://www.technomenace.com/2014/08/how-to-extend-lvm-on-qcow2-images/</ref>. resize2fs code: https://github.com/tytso/e2fsprogs/blob/master/resize/resize2fs.c. See also: [[ext2online]]

== ext4 features timeline==
* 2020 ext4 [[fast commit]] support ([[Linux Kernel 5.10]] December 2020)
* [[2015]] [[File encryption]]
* 2010 Lazy Initialization<ref>https://en.wikipedia.org/wiki/Ext4#Features</ref>
* 2006 Online [[resize]] (expand) support
* 2006 [[Extents]] replace the traditional block mapping scheme used by <code>[[ext2]]</code> and <code>[[ext3]]</code>

== Activities ==
Basic
# Create an file ext4 system using: <code>[[ext4/mkfs.ext4|mkfs.ext4]]</code>
# Create an ext4 file system an [[mount]] it using [[systemd]]: https://codingbee.net/rhcsa/rhcsa-mount-filesystems-during-boot-time-using-systemd

Advanced
# Configure an [[Linux Administration/Devices and Filesystems/LVM|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
# Learn about Lazy initialization feature of ext4: https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem#Lazy_Initialization
# [[Review ext4 journalctl logs]]

== [[Mount options]] ==

== Related terms ==
* <code>[[e2label]]</code>
* [[XFS]]
* [[Reservation percentage]]

== See also ==
* {{ext4}}
* {{filesystems}}
* {{fs}}
* {{Linux filesystem commands}}
* [[ZFS]], [[LVM]], [[mdadm]], [[fdisk]] and [[partitions]]
* {{XFS}}
* [[ext2online]]
* {{JFS2}}
* {{mount}}
* {{Linux Commands privileges}}
* <code>[[smartctl]]</code>

[[Category:Operating systems]]
[[Category:File systems]]
[[Category:Storage]]