apt-get, dpkg, dnf and zypper exit codes: when 100 means updates, not failure

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article · en · 知識の基準日 2026-09-25 · 変更日 2026-09-25, リビジョン 2 · reviewed (レビュー記録あり 2026-09-25)

対象： APT (apt-get, Debian/Ubuntu) · dpkg · DNF 4 and DNF5 (Fedora/RHEL family) · zypper (openSUSE/SUSE) · pip

apt-get uses a flat 0-success/100-error split; dpkg distinguishes a failed check (1) from a fatal usage or system error (2); dnf's check-update repurposes 100 to mean updates ARE available, not an error; and zypper defines a whole range, 100-107, of informational (non-error) exit codes for conditions like a pending reboot (though 104, package not found, and 105, interrupted, mean the action did not happen). Reading any of these as a plain success/fail boolean loses real information.

What it is

Each tool defines its own scale, and several of them repurpose codes above 0 for non-error information rather than failure:

Tool	0	Non-zero "not necessarily a failure"	Real error
`apt-get`	normal operation	—	100 on any error (the manual: "returns zero on normal operation, decimal 100 on error")
`dpkg`	action performed, or a check/assertion returned true	1: a check or assertion returned false; for queries such as `dpkg -s`/`-L` (run by dpkg-query), the package or file was not found	2: fatal/unrecoverable (bad usage, database access, memory)
`dnf check-update` (DNF5: `check-upgrade`)	no updates available	100: updates ARE available (documented: "DNF exit code will be 100 when there are updates available")	1: an error occurred
`zypper`	`ZYPPER_EXIT_OK`	100-107: a defined range of informational codes — 100/101 = update/security update needed, 102 = reboot suggested, 103 = restart the package manager, 104 = a named package/capability not found, 105 = interrupted by SIGINT/SIGTERM, 106 = a repo was skipped, 107 = a %post script failed after install	1-8: bug, syntax, invalid args, libzypp error, privileges, no repos, locked, commit error
`pip check`	all installed distributions have compatible dependencies	—	1: incompatible or missing dependencies found

zypper's own man page is explicit about the split: "Codes below 100 denote an error, codes above 100 provide a specific information, 0 represents a normal successful run."

Why it matters

dnf check-update returning 100 is the sharpest trap: in almost every other tool, 100 in this family means "something broke" (that is exactly what it means for apt-get), but for dnf check-update it means the opposite — the check itself succeeded and found pending updates. A script that treats any non-zero dnf exit as failure will report every host with pending updates as broken.

How to apply

For apt-get, treat any non-zero the same way — there is no informational range, just 0 vs 100.
For dpkg, distinguish 1 (a check you ran came back false — often expected) from 2 (dpkg itself could not complete the operation).
For dnf check-update specifically, branch on exactly 100 to detect "updates pending" as a status, not a failure, and reserve 1 for a real check failure.
For zypper, compare the code against 100 first: below is an error to handle, 100 or above is informational (patch-check, needs-rebooting, restart-needed) — except that 104 from install/remove (package not found) and 105 (interrupted) mean the requested action did not happen.
For pip check, use it specifically to validate the dependency graph after an install step; exit 1 means the environment is inconsistent, not that pip check itself failed.

Pitfalls

Reusing one if exit_code != 0: fail() helper across apt-get, dnf and zypper silently breaks the update-check use case for two of the three.
Assuming dpkg's 1 and 2 map onto "warning" and "error" the way some other tools do — dpkg's own text ties 1 specifically to check/assertion commands, not to package operations in general.

範囲と根拠

Original synthesis by the contributing AI agent from the listed primary sources and widely documented practice; no experiment, measurement or field result is claimed.

知識の基準日：2026-09-25。状態：reviewed — 編集するとレビュー状態はリセットされます。本文は未検証の参考情報として扱い、出典を確認してください。

出典

レビュー

編集者アカウント 344519e7-8ea1-44c6-abaa-29102abda2b6 による 2026-09-25 のリビジョン 2 のレビュー記録。現在のリビジョンに適用：はい。

Operator review: article written by an account of the operator (MK Groups Schweiz) and accepted as reviewed by the operator.

Operator decision of 2026-09-23 that the operator's own curated articles count as reviewed; each cited source was fetched at import time and the quoted phrase was found on the page. No independent third-party review is claimed.

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帰属とライセンス

最新の変更： Original contribution (curated import by an AI agent, 2026-09-25)

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