The /etc/sysconfig directory contains some files that control the system's configuration after boot. The contents of this directory depend on the packages that you have installed on the system. The /etc/sysconfig directory largely provides a single view of many configuration files that are used by systemd and related components that control system configuration, such as Network Manager. In newer releases of Oracle Linux, the number of configuration files in this directory is diminishing because configuration is better handled by systemd and other configuration units. For more information about systemd, see Oracle Linux 8: Managing the System With systemd.

Certain files that you might find in the /etc/sysconfig directory include the following:

atd

Specifies command line arguments for the atd daemon.

autofs

Defines custom options for automatically mounting devices and controlling the operation of the automounter.

crond

Passes arguments to the crond daemon at boot time.

chronyd

Passes arguments to the chronyd daemon used for NTP services at boot time.

firewalld

Passes arguments to the firewall daemon (firewalld) at boot time.

grub

Specifies default settings for the GRUB 2 bootloader. This file is a symbolic link to /etc/default/grub. For more information, see About the GRUB 2 Bootloader.

named

Passes arguments to the name service daemon at boot time. The named daemon is a Domain Name System (DNS) server that's part of the Berkeley Internet Name Domain (BIND) distribution. This server maintains a table that associates host names with IP addresses on the network.

samba

Passes arguments to the smbd, nmbd, and winbindd daemons at boot time to support file-sharing connectivity for Windows clients, NetBIOS-over-IP naming service, and connection management to domain controllers.

selinux

Controls the state of SELinux on the system. This file is a symbolic link to /etc/selinux/config.

For more information, see Oracle Linux: Administering SELinux.

snapper

Defines a list of btrfs file systems and thinly provisioned LVM volumes whose contents can be recorded as snapshots by the snapper utility.

For more information, see Oracle Linux 8: Managing Local File Systems .

sysstat

Configures logging parameters for system activity data collector utilities such as sar.

For more information, see /usr/share/doc/initscripts*/sysconfig.txt.

The files in the /proc directory hierarchy contain information about the system hardware and the processes that are running on the system. You can change the configuration of the kernel by writing to certain files that have write permission.

Files that are under the /proc directory are virtual files that the kernel creates on demand to present a view of the underlying data structures and system information. As such, /proc is an example of a virtual file system. Most virtual files are listed as 0 bytes in size, but they contain large amount of information when viewed.

Virtual files such as /proc/interrupts, /proc/meminfo, /proc/mounts, and /proc/partitions provide a view of the system's hardware. Other files, such as /proc/filesystems and the files under /proc/sys, provide information about the system's configuration and through which you can change configurations as needed.

Files that contain information about related topics are grouped into virtual directories. A separate directory exists in the /proc directory for each process that's running on the system. The directory's name corresponds to the numeric process ID. For example, /proc/1 corresponds to the systemd process that has a PID of 1.

To examine virtual files, you can use commands such as cat, less, and view, as shown in the following example:

cat /proc/cpuinfo

processor         : 0
vendor_id         : GenuineIntel
cpu family        : 6
model             : 42
model name        : Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz
stepping          : 7
cpu MHz           : 2393.714
cache size        : 6144 KB
physical id       : 0
siblings          : 2
core id           : 0
cpu cores         : 2
apicid            : 0
initial apicid    : 0
fpu               : yes
fpu_exception     : yes
cpuid level       : 5
wp                : yes
...

For files that contain non human-readable content, you can use utilities such as lspci, free, top, and sysctl to access information. For example, the lspci command lists PCI devices on a system:

sudo lspci

00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
00:01.1 IDE interface: Intel Corporation 82371AB/EB/MB PIIX4 IDE (rev 01)
00:02.0 VGA compatible controller: InnoTek Systemberatung GmbH VirtualBox Graphics Adapter
00:03.0 Ethernet controller: Intel Corporation 82540EM Gigabit Ethernet Controller (rev 02)
00:04.0 System peripheral: InnoTek Systemberatung GmbH VirtualBox Guest Service
00:05.0 Multimedia audio controller: Intel Corporation 82801AA AC'97 Audio Controller (rev 01)
00:06.0 USB controller: Apple Inc. KeyLargo/Intrepid USB
00:07.0 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 08)
00:0b.0 USB controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB2 EHCI Controller
00:0d.0 SATA controller: Intel Corporation 82801HM/HEM (ICH8M/ICH8M-E) SATA Controller [AHCI mode]
        (rev 02)
...

See procfs Directory Reference for more information about the different directories available under /proc. See Managing Kernel Parameters at Runtime for information on how you can view and change kernel parameters in /proc/sys to control system runtime behavior.

In addition to the /proc file system, the kernel exports information to the /sys virtual file system (sysfs). Programs such as the dynamic device manager (udev), use /sys to access device and device driver information. See Oracle Linux 8: Managing System Devices With udev for more information about device management.

See sysfs Directory Reference to see more information about the directories that you can find in /sys.