OLE key terms

Oracle's own Linux kernel build, based on a recent upstream mainline release, shipped alongside the Red Hat Compatible Kernel. It provides newer drivers and features and is the default kernel on current Oracle Linux installs.

The kernel package that mirrors the upstream Red Hat Enterprise Linux kernel ABI, offered as an alternative to UEK for workloads needing strict RHEL compatibility. Selected by installing the kernel package and setting it as default in the bootloader.

Oracle's zero-downtime kernel patching technology. An uptrack kernel module applies accumulated patches to the running kernel in memory, so security fixes take effect without rebooting the system.

A copy-on-write filesystem available in Oracle Linux offering snapshots, subvolumes, compression, and built-in RAID. Oracle supports it as a technology preview in some releases, so check support status before production use.

Unbreakable Linux Network is Oracle's hosted repository and patch service for Oracle Linux systems. Systems register with ULN (or a local Oracle Linux Manager server) to receive errata and package updates.

Oracle's public, free package repository at yum.oracle.com providing base, updates, and add-on channels for Oracle Linux, including UEK and EPEL-style extras. Configured through repository files under /etc/yum.repos.d.

The DNF package manager used on Oracle Linux 8 and later, replacing yum. It resolves dependencies using libsolv, supports transaction history, module streams, and repository management through /etc/yum.repos.d.

The low-level RPM Package Manager that installs, upgrades, queries, and verifies individual .rpm packages. It does not resolve dependencies automatically, so dnf is normally used for installation.

A record of every dnf transaction, viewable with dnf history list and reversible with dnf history undo. Useful for auditing changes and rolling back a bad package update.

Verification that an RPM package was signed by a trusted key before installation. Enabled with gpgcheck=1 in repository files; the key is imported with rpm --import.

A storage layer on top of physical volumes and volume groups that provides flexible, resizable block devices. Logical volumes can be extended online and support snapshots and striping.

A disk partition or whole disk initialized with pvcreate for use by LVM. It carries metadata describing its volume group and the physical extents available for allocation.

A pool of physical extents formed from one or more physical volumes. Logical volumes are carved out of this pool, and the group can be extended by adding PVs with vgextend.

The static filesystem table read at boot to mount devices by UUID, label, or path. Errors here can prevent booting, so use mount -a and systemd mount units to validate changes.

A generated unit such as var-log.mount that represents a mount point and its dependencies. Units are derived from /etc/fstab and can be inspected with systemctl list-units --type=mount.

The default network management service on Oracle Linux, configured with nmcli or nmtui. It manages connections as profiles that can be activated per device and persist across reboots.

The NetworkManager command-line client used to create, modify, activate, and inspect connection profiles. Example: nmcli connection add type ethernet ifname eth0 con-name lan1.

The primary command for controlling systemd units: starting, stopping, enabling, and inspecting services, sockets, timers, and targets. It also reports unit failures and dependency trees.

A unit pair (.timer and .service) that schedules recurring or one-shot jobs as an alternative to cron. Timers support calendar expressions, persistence across downtime, and journal logging.

The per-user and system job scheduler table edited with crontab -e and stored under /var/spool/cron. Fields specify minute, hour, day, month, weekday, then the command to run.

A mandatory access control framework enforcing type-based policy on processes and files. Modes are enforcing, permissive, and disabled; context problems are the most common cause of denied access.

A tool from policycoreutils-python-utils that sets persistent SELinux file-context rules. After adding a rule, run restorecon to relabel existing files to the new context.

A command that resets file SELinux contexts to match the policy database. Run with -Rv to recursively relabel a directory tree after context rules change.

The default host firewall service on Oracle Linux, managed with firewall-cmd. It organizes rules into zones and supports runtime versus permanent configuration.

The firewalld client used to add services, ports, and rich rules to zones. Changes are runtime by default; add --permanent and reload to persist them.

The bootloader used on Oracle Linux, configured in /boot/grub2/grub.cfg and regenerated with grub2-mkconfig. It presents the kernel menu and passes kernel command-line arguments.

A command-line tool that edits GRUB 2 configuration entries, such as setting the default kernel or adding kernel arguments. Changes apply to the generated grub.cfg without manual editing.

The tool that builds the initramfs image loaded by the kernel at boot. Regenerate it after storage or driver changes with dracut -f to avoid boot failures.

Loads or removes kernel modules while resolving dependencies, unlike insmod which loads a single file. Configuration lives in /etc/modprobe.d and persistent options in modprobe.d files.

Lists currently loaded kernel modules by reading /proc/modules. Used together with modinfo to inspect module parameters and dependencies.

The command to query the systemd journal, which collects kernel and service logs. Supports filtering by unit, priority, boot, and time, and persistent storage via /var/log/journal.

The traditional syslog daemon that writes text logs under /var/log based on rules in /etc/rsyslog.conf. Often runs alongside the journal for centralized or file-based logging.

A utility that rotates, compresses, and deletes log files according to rules in /etc/logrotate.conf and /etc/logrotate.d. Prevents filesystems from filling with old logs.

Monitoring tools for live and historical performance data. top shows current process and CPU usage; sar, from the sysstat package, reports collected CPU, memory, and I/O statistics over time.

Commands to create and modify local user accounts, including home directory, shell, UID, and supplementary groups. Defaults come from /etc/default/useradd and /etc/login.defs.

Files holding user account information and encrypted password hashes respectively. /etc/shadow is readable only by root and supports password aging and account locking.

A value that determines default permissions removed from newly created files and directories. A umask of 022 yields 644 for files and 755 for directories.

Tooling in Oracle Linux cloud images that configures instances at first boot, such as network, SSH keys, and user data. cloud-init reads metadata from the instance metadata service.