主题： rhel
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Checking whether a Linux host needs a reboot or a service restart after updates
Debian and Ubuntu mark a pending reboot with the plain file /var/run/reboot-required, while RHEL-family systems require comparing the running kernel to the newest installed one or running a needs-restarting-style check; neither family tells you this automatically at the shell prompt.
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Verifying installed RPM packages for tampering with rpm -V
rpm -V compares installed files against the checksums, permissions and ownership recorded when the package was installed, and its single-letter output codes say exactly what changed. This methodology covers reading that output and its limits as an integrity check.
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Administering a headless RHEL host through the Cockpit web console
Cockpit gives a browser-based admin session to a RHEL server with no desktop GUI, socket-activated so it only starts on first connection. This methodology covers enabling it, opening the firewall with its own named service, and what it is actually useful for on a server.
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Planning an in-place major upgrade of RHEL with Leapp
Leapp upgrades RHEL 8 to 9, or 9 to 10, in place, but only after every upgrade-blocking finding in its preupgrade report is resolved. This methodology covers running the assessment, recording answers to its prompts, and why a backup comes before the actual upgrade step.
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Choosing and layering performance profiles with tuned on RHEL
tuned applies a named bundle of kernel and system tunables as one profile switch, and a custom profile can inherit from an existing one and override only what differs. This methodology covers listing, recommending, applying and building on top of profiles.
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Managing firewalld zones and rules without locking yourself out over SSH
firewalld separates a running configuration from a permanent one, and a plain firewall-cmd change is lost on the next reload unless made permanent. This methodology covers zones, the runtime/permanent split, rich rules, and testing a change before it becomes unrecoverable over a remote SSH session.
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Application Streams and DNF modules on RHEL: what RHEL 10 changes
RHEL 8 and 9 deliver part of AppStream as DNF modules, letting more than one version of a component exist for one OS release with only one stream active at a time. RHEL 10's own rebuilds document modularity as deprecated, with Application Stream packages installing directly instead.
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Registering a RHEL system and enabling repositories with subscription-manager and dnf
Registering RHEL, enabling the repositories a workload needs, and pinning a minor release are three separate steps with subscription-manager and dnf. This methodology covers non-interactive registration, verifying content access, and when release pinning is actually appropriate.
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Podman rootless versus rootful on RHEL-family hosts: storage, subuid, and lingering
Podman runs containers as an ordinary user (rootless) or as root (rootful), with different storage locations and privilege boundaries. This methodology covers inspecting running containers, finding storage paths, setting up subordinate UID/GID ranges, and keeping rootless services alive without a login session.
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Switching system-wide crypto policies on RHEL with update-crypto-policies
RHEL's system-wide crypto policy sets the default algorithms and protocol versions OpenSSL, GnuTLS, NSS, libkrb5 and OpenSSH offer, changeable in one command instead of editing every application's config. This methodology covers showing, setting and testing a policy, and why already-running services need a restart to pick it up.
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Triaging SELinux denials without disabling enforcement on RHEL
Most SELinux denials on RHEL are fixed with a boolean, a file context relabel or a port addition, all reversible and none requiring enforcement to be turned off. This methodology walks from finding a denial to applying and verifying the narrowest fix.
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Building an unattended RHEL install with a Kickstart file
A Kickstart file drives a RHEL, Rocky Linux or AlmaLinux install with no interactive prompts, combining one-line commands with %pre and %post scriptlets. This methodology covers validating the file before use, passing it at boot, and keeping secrets out of a file that is often served unauthenticated.
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Configuring kdump to capture a RHEL kernel crash
kdump reserves memory ahead of time so a second, minimal kernel can boot after a panic and write out a vmcore for analysis. This methodology covers reserving that memory, enabling the service, and why deliberately testing it takes down the host — schedule the test accordingly.
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Undoing a dnf transaction and locking package versions on RHEL
dnf keeps a full transaction history that can be inspected, undone or rolled back, and the versionlock mechanism pins a package to its current version across later updates. This methodology covers both, the difference between undo and rollback, and what differs in DNF5 on current Fedora.
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