OLE flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

UEK vs RHCK

UEK is Oracle's Unbreakable Enterprise Kernel, default on Oracle Linux and optimized for Oracle workloads; RHCK is the Red Hat Compatible Kernel available as an alternative boot entry.

Kickstart inst.ks

Boot parameter that points the installer to a Kickstart file (URL, NFS, or disk path) to automate partitioning, package selection, and post-install configuration.

oracle-database-preinstall package

RPM that configures kernel parameters, limits, and the oracle user/group recommended for Oracle Database installations on Oracle Linux.

sos report

Support tool that collects system configuration, logs, and diagnostics into a compressed archive under /var/tmp for analysis by Oracle Support.

rpm -qf

RPM query option that identifies which installed package owns a given file path, useful when tracing configuration file origins.

dnf history

DNF subcommand that lists past transactions; use dnf history undo ID to revert a transaction or dnf history info ID for details.

ULN registration

Unbreakable Linux Network requires a support subscription; register with uln_register and manage channels with uln-channel to receive updates.

AppStream modules

DNF modules group packages by stream (version); enable a stream with dnf module enable name:stream before installing to select the desired software version.

lvextend and xfs_growfs

lvextend increases a logical volume size; xfs_growfs then expands the mounted XFS filesystem to use the new space without unmounting.

fstab UUID mounts

Using UUID= in /etc/fstab provides persistent device identification across reboots, avoiding device name changes; obtain UUIDs with blkid.

XFS shrink limitation

XFS filesystems cannot be shrunk; plan sizes carefully or back up, recreate, and restore data if a smaller filesystem is required.

findmnt --verify

Command that checks /etc/fstab syntax and mount point validity without mounting, helping prevent boot failures from fstab errors.

nmcli connection add

Creates a NetworkManager connection profile; specify type, interface, IP method, addresses, gateway, and DNS in one command.

systemctl enable

Creates symlinks so a unit starts automatically at boot; use --now to also start it immediately. Disable reverses the symlinks.

ss -tulpn

Lists listening TCP and UDP sockets with numeric ports and owning process names/PIDs, useful for checking service availability.

nmcli con reload

Tells NetworkManager to reread connection profile files from /etc/NetworkManager/system-connections after manual edits.

chage -d 0

Sets the last password change date to zero, forcing the user to change their password at the next login.

setfacl and getfacl

setfacl modifies POSIX ACLs (e.g., setfacl -m u:user:rw file); getfacl displays ACL entries for a file or directory.

umask calculation

Default permissions are derived by subtracting umask from 666 for files and 777 for directories; umask 022 yields 644 files and 755 directories.

visudo

Safe editor for /etc/sudoers that locks the file and validates syntax before saving, preventing broken sudo configuration.

grub2-mkconfig

Regenerates GRUB 2 configuration from /etc/default/grub and /etc/grub.d scripts; output typically /boot/grub2/grub.cfg.

dracut -f

Rebuilds the initramfs for the running kernel, required after storage driver or kernel changes to ensure boot succeeds.

rd.break boot parameter

Kernel command line option that interrupts boot in the initramfs, providing a root shell for recovery such as resetting passwords.

journalctl -b -1

Displays journal entries from the previous boot, useful for diagnosing why a system failed to start normally.

sar and sysstat

sar collects and reports historical CPU, memory, I/O, and network statistics; sysstat package provides it and enables data collection.

logrotate

Rotates, compresses, and removes old log files based on rules in /etc/logrotate.conf and /etc/logrotate.d/ to control disk usage.

systemd-analyze blame

Lists systemd units sorted by boot time, helping identify services that delay startup.

setenforce 0

Switches SELinux to permissive mode at runtime (logging denials without enforcing); does not persist across reboots.

restorecon -Rv

Recursively resets SELinux file contexts to the policy default and displays changes; used after moving files into new locations.

firewall-cmd --permanent

Makes a firewalld rule persistent across reloads and reboots; must follow with firewall-cmd --reload to activate.

systemd timer OnCalendar

Timer unit setting that schedules activation using calendar syntax (e.g., daily, *-*-* 03:00:00); paired service unit runs the job.

crontab fields

Five time fields (minute, hour, day of month, month, day of week) followed by the command; user crontabs edited with crontab -e.

Ksplice uptrack-upgrade

Applies available Ksplice kernel updates to the running kernel without reboot; requires Ksplice client and subscription access.