すべての記事
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訓練・検証・テスト集合：各分割の役割と分け方
モデルは訓練集合で適合し、モデルやハイパーパラメーターは検証集合、または交差検証で選び、テスト集合には最終推定のために一度だけ触れる。行を無作為、層化、グループ別、時系列のどれで割り当てるかによって、推定が本番について何かを示すかどうかが決まる。
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Managing FileVault from the command line: status, recovery keys, secure token and bootstrap token
fdesetup reports and changes FileVault state and recovery-key handling; sysadminctl and profiles report which accounts can unlock the disk and whether a bootstrap token is escrowed with a device management service, which matters before relying on MDM-driven account provisioning.
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When should a service with users in every time zone schedule its maintenance window?
Open question: a maintenance window at 3 a.m. locally is midday for someone; how have small teams serving global users chosen their windows, and did traffic-minimum, staff-availability or rotating-region windows lead to fewer complaints and safer changes?
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Lesbarer Fliesstext: Zeilenlänge, Zeilenabstand und Kontrast
Drei Eigenschaften entscheiden, ob langer Text bequem lesbar ist: die Zeilenlänge (das AAA-Kriterium der WCAG deckelt sie bei 80 Zeichen), der Zeilenabstand (mindestens das 1,5-Fache der Schriftgrösse muss möglich sein, ohne dass das Layout bricht) und der Kontrast (4,5:1 für normalen Text, 3:1 für grossen). In relativen Einheiten setzen, damit Nutzende Text vergrössern und neu spationieren können.
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Godot TileMapLayer: Author Tile Identity, Terrain Rules and Collision Together
Organize tile layers around their role, keep map coordinates separate from atlas identity, and prepare complete terrain and collision data before relying on automatic painting.
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Checking a kitchen scale with coins of published mass: a repeatability, range and corner-load record
A proposed record-only protocol for a household scale: use new coins whose nominal mass the issuing mint publishes as reference masses, log readings for single coins and stacks across the scale's range, repeat placements, test the four corners and a timed hold, and keep the sheet per scale; no adjustment and no pass or fail judgement is part of it.
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Where Solaris keeps its logs, and using fmadm/fmdump for hardware and software faults
General system messages accumulate in /var/adm/messages (what dmesg replays), each SMF instance logs its own start-method output under /var/svc/log/, and the Fault Management Architecture (fmadm, fmdump) separately diagnoses hardware and some software faults into a correlated record with a UUID.
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Booting a rescue or live system and chrooting into an installed Linux to repair it
When a system will not boot at all, the standard recovery path is to boot an independent rescue or live medium, mount the installed root and its related filesystems, bind-mount the kernel's virtual filesystems into it, chroot in to run the installed system's own tools (grub-install, package manager, passwd), then unmount everything cleanly before rebooting.
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HEAD と OPTIONS：何を回答し、クライアントは何に使うか
HEAD は本文のない GET であり、ステータスとヘッダーは同じだが、Content-Length と Vary は省略できる。キャッシュ可能で、リンク、サイズ、鮮度の確認に使う。OPTIONS はリソースまたはサーバー全体（OPTIONS *）の通信オプションを問い合わせ、通常は Allow を返す。キャッシュ不可で、Access-Control-Request-Method を伴う CORS プリフライトにも使う。
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Verifying Slack request signatures: X-Slack-Signature, the 5-minute replay window and the 3-second rule
Slack signs requests as v0=<hex HMAC-SHA256> of the string "v0:{timestamp}:{raw body}" in the X-Slack-Signature header, paired with X-Slack-Request-Timestamp, which Slack's own example rejects once it differs from local time by more than five minutes. Slash commands and interactive payloads must additionally be acknowledged within three seconds, before any slow processing.
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Administering DNS Server zones and records from PowerShell, then verifying with Resolve-DnsName
Get-DnsServerZone, adding A and CNAME records, listing records with Get-DnsServerResourceRecord, the scavenging/aging settings that expire stale records, and clearing the resolver cache — with every write checked from the client side, not just the server's own view.
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IIS administration basics from PowerShell: sites, app pools, logs, and backing up the configuration
Reading sites with the IISAdministration module's Get-IISSite, recycling an application pool, where IIS writes its logs by default, and using appcmd add backup to snapshot applicationHost.config before a configuration change.
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Unity Burst and Jobs: Design Dependencies Around Shared Native Data
Structure Burst-compatible computation as producers and consumers, declare native-container access, and complete the final dependency before the main thread reads or disposes shared memory.
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Per-process CPU and I/O with pidstat and /proc/<pid>/io: finding what causes I/O wait
pidstat reports per-task CPU, memory and disk I/O without grepping a name out of top; reading /proc/<pid>/io directly separates logical I/O (rchar/wchar, including cache) from the physical read_bytes/write_bytes that actually reach the device.
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Read-only maintenance mode: serving reads while writes are paused
For storage moves, failovers and long migrations, a service can keep serving reads and refuse writes with a clear message instead of going dark; PostgreSQL's default_transaction_read_only makes new transactions read-only at the database as a backstop, and HTTP 503 with Retry-After tells clients when to try again. The mode needs one switch, a user-facing message and a rehearsal.
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Godot CharacterBody3D: grounded motion with correct velocity and physics timing
Keep velocity in distance-per-second units, integrate acceleration deliberately and use move_and_slide during physics updates with explicit grounded-state rules.
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Maven versus Gradle: what a newcomer needs to build someone else's JVM project
Maven describes a project declaratively in pom.xml and runs fixed lifecycle phases (validate, compile, test, package, verify, install, deploy) with plugin goals bound to them; Gradle runs a graph of tasks configured by build.gradle(.kts) scripts and plugins. Both resolve transitive dependencies but with different conflict rules (Maven: nearest definition; Gradle: highest version), and both ship a wrapper script that pins the build tool version.
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TLS verification errors across tools: unknown authority, CERTIFICATE_VERIFY_FAILED, self-signed in chain
Different TLS clients report the same underlying failure - an incomplete or untrusted certificate chain - in their own wording: 'certificate signed by unknown authority', 'CERTIFICATE_VERIFY_FAILED', 'unable to get local issuer certificate', 'self-signed certificate in certificate chain'. The article shows how to diagnose the actual chain with openssl s_client before reaching for any fix, and why -k or verify=False is never one.
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Pythonの処理にスレッド、プロセス、asyncioのどれを選ぶか
まず頻繁に通る処理経路を分類します。I/O待ちにはasyncio（多数の接続、非同期ライブラリ）かスレッドプール（少数のブロッキング呼び出し）が向きます。純粋なPythonのCPU処理にはプロセスかフリースレッドビルドが必要で、GILを解放するネイティブコードにはスレッドを使えます。各プールに上限を設け、プロセスの起動方式を明示し、終了処理を書きます。
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Installing, updating and verifying software with the Image Packaging System (pkg)
The pkg client covers search, install, update, uninstall, publisher management, and verify/fix against packaging metadata. pkg operations are boot-environment aware: changes to packages that require a reboot go into a new BE activated for the next boot, while other changes apply to the running BE, under the default policy with a backup BE when kernel-affecting content is touched.
機械可読： JSON