A filesystem (aka filesystem) is the software structure (the formatting) that is located on a storage device or in memory, and dictates how data is organized there.
When a filesystem is located on a storage device, like a disk or DVDROM, then it is called a physical filesystem. When it is located in memory, like for example when the Linux kernel loads the proc filesystem in RAM, then it is called a virtual filesystem.
When referring to storage capacities, there are two units of measurements:
Commands that use units of 1024 bytes: fdisk, lsblk, sfdisk, etc.
user1@rhel10-vm2:~$ ls /usr/lib/tuned/profiles
accelerator-performance balanced desktop intel-sst network-latency optimize-serial-console throughput-performance virtual-host
aws balanced-battery hpc-compute latency-performance network-throughput powersave virtual-guest
user1@rhel10-vm2:~$
Verify that the tuned service is installed with DNF:
user1@rhel10-vm2:~$ dnf list --installed | grep tuned
tuned.noarch 2.25.1-2.el10_0 @rhel-10-for-x86_64-baseos-rpms
Verify the status of the service with systemctl:
user1@rhel10-vm2:~$ systemctl status tuned
● tuned.service - Dynamic System Tuning Daemon
Loaded: loaded (/usr/lib/systemd/system/tuned.service; enabled; preset: enabled)
Active: active (running) since Fri 2026-08-21 19:29:51 CEST; 1h 15min ago
Invocation: fa8cec68b5b449ee9d4f13e2ef0a4618
Docs: man:tuned(8)
man:tuned.conf(5)
man:tuned-adm(8)
Main PID: 936 (tuned)
Tasks: 4 (limit: 10680)
Memory: 17.7M (peak: 19.7M)
CPU: 952ms
CGroup: /system.slice/tuned.service
└─936 /usr/bin/python3 -Es /usr/sbin/tuned -l -P
Warning: some journal files were not opened due to insufficient permissions.
user1@rhel10-vm2:~$
Display the list of available tuning profiles:
Syslogs contain subsets of information on faults, events, audit & session data, all related the monitored objects. Not all logs depict errors. Syslog can include audit and event logs.
Any program or process capable of generating syslogs.
aka syslog severity levels or syslog priorities. The describe different levels of importance. Example of syslog severities: emergency, alert, critical, informational, warnings.
Verify the version of rsyslogd deployed on a RHEL machine:
The Linux kernel is not a monolithic file but rather a set of RPM packages.
Find out the installed kernel packages:
user1@localhost:~$ rpm -qa *kernel*
kernel-modules-extra-matched-6.12.0-124.8.1.el10_1.x86_64
kernel-tools-libs-6.12.0-124.8.1.el10_1.x86_64
kernel-modules-core-6.12.0-124.8.1.el10_1.x86_64
kernel-core-6.12.0-124.8.1.el10_1.x86_64
kernel-modules-6.12.0-124.8.1.el10_1.x86_64
kernel-modules-extra-6.12.0-124.8.1.el10_1.x86_64
kernel-tools-6.12.0-124.8.1.el10_1.x86_64
kernel-6.12.0-124.8.1.el10_1.x86_64
user1@localhost:~$
Find out the kernel version and release:
user1@localhost:~$ uname --help
Usage: uname [OPTION]...
Print certain system information. With no OPTION, same as -s.
-a, --all print all information, in the following order,
except omit -p and -i if unknown:
-s, --kernel-name print the kernel name
-n, --nodename print the network node hostname
-r, --kernel-release print the kernel release
-v, --kernel-version print the kernel version
-m, --machine print the machine hardware name
-p, --processor print the processor type (non-portable)
-i, --hardware-platform print the hardware platform (non-portable)
-o, --operating-system print the operating system
--help display this help and exit
--version output version information and exit
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Full documentation <https://www.gnu.org/software/coreutils/uname>
or available locally via: info '(coreutils) uname invocation'
user1@localhost:~$
user1@localhost:~$ uname -v
#1 SMP PREEMPT_DYNAMIC Fri Oct 17 13:03:58 EDT 2025
user1@localhost:~$ uname -r
6.12.0-124.8.1.el10_1.x86_64
user1@localhost:~$
With the exception of the efi and grub2 directories, which deal with the bootloader for UEFI and BIOS systems respectively, the rest of the files and subdirectories under the /boot/ directory are related to the kernel.
On a BIOS machine, GRUB2 does not exist as a monolithic file. It takes more than one shape and form, depending on the boot stage. The first form of GRUB2 is a binary code on a section on the MBR of a bootable disk. Once the linux firmware locates the first form of GRUB2, it loads it in memory. The program then relies on the GRUB2-related files under /boot/ and /etc/ to respectively load the main image of GRUB2 and read the configuration.
Read this technote
A Flatpak remote is a local representation of an online Flatpak repository. It can be a statically defined ‘.flatpakrepo’ file, manually placed under ‘/etc/flatpak/repos.d/’, or a dynamically defined section of the active configuration file, which is the ‘/var/lib/flatpak/repo/config’ file.
The addition of a description of a Flatpak remote in the active configuration file is performed by the Flatpak tool, when the command flatpak remote-add is executed.
Units are configuration files that describe the resources that are managed by systemd. They are stored in four file system paths. If I do a manual search I can approximately tell where they are:
Wassim@linux:~$ find / -mindepth 1 -name systemd 2>/dev/null
/home/Wassim/Documents/ddupdate/systemd
/home/Wassim/.config/systemd
/run/systemd
/run/udev/tags/systemd
/run/user/1000/systemd
/etc/xdg/systemd
/etc/systemd
/var/lib/systemd
/var/lib/flatpak/runtime/org.gnome.Platform/x86_64/49/e51263e53d04900556e2f97ac2b27201f632f604d68d67f50323f9a99389fdb0/files/lib/systemd
/var/lib/flatpak/runtime/org.gnome.Platform/x86_64/49/e51263e53d04900556e2f97ac2b27201f632f604d68d67f50323f9a99389fdb0/files/share/licenses/gnome/systemd
/var/lib/flatpak/runtime/org.gnome.Platform/x86_64/50/a8da766dd0273a67539d2b98358ed6809d8e729280baf63428108837135229d3/files/lib/systemd
<---- output omitted ---->
/var/lib/snapd/snap/gnome-3-38-2004/143/usr/lib/systemd
/usr/lib/systemd
/usr/lib/systemd/systemd
/usr/lib64/systemd
/usr/lib64/python3.12/site-packages/systemd
/usr/share/licenses/systemd
/usr/share/doc/systemd
/usr/share/systemd
/usr/share/cockpit/systemd
Wassim@linux:~$
/run/systemd seem to store runtime unit files, because /run/ typically contains runtime data, so it can not be a permanent location of systemd unit files. There is also /etc/systemd and /usr/lib/systemd/system/. The latter appears to store system units:
List the enabled repos: either with dnf repolist or dnf repolist --enabled. I can add the verbose option -v.
user1@localhost:~$ dnf repolist -v
Loaded plugins: builddep, changelog, config-manager, copr, debuginfo-install, download, generate_completion_cache, groups-manager, kpatch, needs-restarting, notify-packagekit, playground, product-id, repoclosure, repodiff, repograph, repomanage, reposync, subscription-manager, system-upgrade, uploadprofile
Not root, Subscription Management repositories not updated
DNF version: 4.20.0
cachedir: /var/tmp/dnf-user1-w76vxc5s
OS software 2.7 MB/s | 2.7 kB 00:00
Application software 2.7 MB/s | 2.8 kB 00:00
Repo-id : AppStream
Repo-name : Application software
Repo-revision : 1761027148
Repo-updated : Tue 21 Oct 2025 08:12:28 AM CEST
Repo-pkgs : 4,514
Repo-available-pkgs: 4,514
Repo-size : 6.5 G
Repo-baseurl : file:///mnt/AppStream
Repo-expire : 172,800 second(s) (last: Sat 04 Jul 2026 10:29:26 PM CEST)
Repo-filename : /etc/yum.repos.d/local.repo
Repo-id : baseOS
Repo-name : OS software
Repo-revision : 1761027164
Repo-updated : Tue 21 Oct 2025 08:12:45 AM CEST
Repo-pkgs : 946
Repo-available-pkgs: 946
Repo-size : 1.3 G
Repo-baseurl : file:///mnt/BaseOS
Repo-expire : 172,800 second(s) (last: Sat 04 Jul 2026 10:29:26 PM CEST)
Repo-filename : /etc/yum.repos.d/local.repo
Total packages: 5,460
user1@localhost:~$
user1@localhost:~$ dnf repolist --enabled -v
Loaded plugins: builddep, changelog, config-manager, copr, debuginfo-install, download, generate_completion_cache, groups-manager, kpatch, needs-restarting, notify-packagekit, playground, product-id, repoclosure, repodiff, repograph, repomanage, reposync, subscription-manager, system-upgrade, uploadprofile
Not root, Subscription Management repositories not updated
DNF version: 4.20.0
cachedir: /var/tmp/dnf-user1-w76vxc5s
Last metadata expiration check: 0:05:39 ago on Sat 11 Jul 2026 05:38:51 PM CEST.
Repo-id : AppStream
Repo-name : Application software
Repo-revision : 1761027148
Repo-updated : Tue 21 Oct 2025 08:12:28 AM CEST
Repo-pkgs : 4,514
Repo-available-pkgs: 4,514
Repo-size : 6.5 G
Repo-baseurl : file:///mnt/AppStream
Repo-expire : 172,800 second(s) (last: Sat 11 Jul 2026 05:38:51 PM CEST)
Repo-filename : /etc/yum.repos.d/local.repo
Repo-id : baseOS
Repo-name : OS software
Repo-revision : 1761027164
Repo-updated : Tue 21 Oct 2025 08:12:45 AM CEST
Repo-pkgs : 946
Repo-available-pkgs: 946
Repo-size : 1.3 G
Repo-baseurl : file:///mnt/BaseOS
Repo-expire : 172,800 second(s) (last: Sat 11 Jul 2026 05:38:51 PM CEST)
Repo-filename : /etc/yum.repos.d/local.repo
Total packages: 5,460
user1@localhost:~$
#LessonLearned There is no difference in output between dnf repolist -v and dnf repolist --enabled -v.