LSB Core IA-32 is the X86-specific part of the Linux Standard Base (LSB) Core specification. It must be read together with the generic LSB Core document: the generic text defines common requirements, while IA-32 adds processor, binary-format, dynamic-linking and library requirements for 32-bit X86 systems.
The LSB is primarily a binary-interface definition, not a complete source-level Linux API catalogue. It describes interfaces that compiled applications can rely on and the minimum environment needed by installation scripts.
What LSB Core IA-32 covers
IA-32 is the architecture-specific supplement for 32-bit X86. The generic Core and the IA-32 Core together provide the relevant Core interface specification for this architecture.
- Generic Core: requirements intended to apply across supported architectures.
- IA-32 Core: additions and variations that depend on the X86 processor architecture and its binary environment.
Consulting only the IA-32 document gives an incomplete picture; common requirements remain in the generic Core.
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API, ABI, or operating-system distribution?
LSB Core IA-32 is chiefly an ABI and binary-compatibility specification. It defines interfaces and runtime behavior for compiled programs, along with requirements for an implementation that claims conformance. It is not a promise that every current Linux distribution implements every LSB requirement, nor is it a replacement for a distribution’s ordinary developer documentation.
The specification also directs applications to use base-library interfaces rather than calling an implementation’s underlying system-call interface directly. That distinction allows the implementation to provide the standardized behavior without making raw kernel entry points the application’s portability contract.
Required runtime names in the 5.0 IA-32 text
The Linux Foundation-hosted 5.0 edition lists runtime names that a conforming IA-32 environment is expected to provide. These are compatibility requirements, not evidence that a particular modern installation supplies them.
| Category | Name listed by the specification | Why it matters when diagnosing a binary |
|---|---|---|
| C library | libc.so.6 |
A required shared-library name that may be requested by a binary. |
| POSIX threads library | libpthread.so.0 |
A required shared-library name for binaries that declare this dependency. |
| GNU C++ library | libstdc++.so.6 |
A required shared-library name for binaries linked against the listed C++ runtime. |
| LSB program interpreter | /lib/ld-lsb.so.3 |
The specified interpreter path used to begin dynamic loading for the supported binary format. |
At launch, the program interpreter must load the shared libraries named by the executable’s DT_NEEDED entries. Consequently, a program can fail before its own code runs if an expected interpreter or library name is absent, even when the processor itself is capable of executing the instructions.
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The 5.0 specification states: “Only the features of the Intel486 processor instruction set may be assumed to be present.” This is the minimum contract for that edition, not a description of what contemporary processors normally support.
What an application may do
- Assume the Intel486 instruction-set baseline specified by the document.
- Detect additional processor features before using instructions beyond that baseline.
- Use the standardized base-library interfaces instead of directly invoking implementation-specific system-call entry points.
What an application must not assume
- It must not assume later instruction extensions merely because most machines in use have them.
- It must not execute privileged instructions as ordinary application code.
These rules matter when investigating an old 32-bit executable: a missing library name and an unsupported instruction are different failure classes and require different remedies.
What conformance means
Conformance applies to both sides of the interface.
Conforming implementation
A conforming implementation provides the generic and architecture-specific interfaces, can execute applications using the specified object format and interfaces, and supplies the required libraries and dynamic-linking mechanism described by the specification.
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Conforming application
An application is expected to use the specified interfaces and binary conventions, stay within the processor assumptions, and avoid relying on implementation details outside the LSB contract.
A distribution may run many LSB-oriented binaries without claiming formal LSB conformance. The specification’s requirements and the actual contents of a particular installation are separate questions.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to use the specification when a 32-bit binary fails
- Identify the architecture. Confirm that the executable is 32-bit X86 rather than a different architecture or bitness.
- Inspect declared dependencies. Compare the executable’s
DT_NEEDEDentries with the library names required by the environment. - Check the interpreter path. A binary expecting
/lib/ld-lsb.so.3cannot start if that path is unavailable, regardless of whether another loader exists elsewhere. - Separate naming from implementation. A library with a different filename, ABI, or incompatible symbol set is not automatically a substitute for the name and interface the binary requests.
- Check instruction assumptions. If loading succeeds but execution faults, investigate use of instructions beyond the Intel486 baseline and whether the application detected their availability.
- Verify the target edition. Requirements in the hosted 5.0 text should not be silently treated as the requirements of every later publication.
Which edition should you cite?
The Linux Foundation-hosted material identifies a 5.0 edition with a 2015 copyright. IEC’s catalogue separately lists ISO/IEC 23360-2-2:2021, Core specification for X86-32 architecture. The available evidence does not establish that the IEC 2021 text is technically identical to, or formally supersedes, the hosted 5.0 document.
For a compatibility investigation or a compliance claim, name the exact edition you are using and obtain that edition’s normative text. Do not call either document “the latest LSB IA-32 specification” without verifying the publication status and technical relationship yourself.
LSB Core IA-32 in one sentence
It is the 32-bit X86 supplement to the generic Linux Standard Base Core, defining the processor and binary-runtime assumptions—including interpreter and shared-library names—that an LSB-compatible implementation and application are expected to follow.
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