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Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →A UID range is a contiguous interval of numeric identifiers, but its meaning depends on the system using it. In Linux account administration, ranges help allocate user and service IDs; in Android, they can represent identities in network-policy code; IEEE EUI blocks are a separate identifier system altogether. The allocation rules, scope of uniqueness, and safe values therefore depend on the operating system and management system.
What is a UID range?
A UID range is a start-to-end interval of numeric identifiers. Software can use that interval to decide which IDs are available, reserved, assigned to a class of accounts, or considered part of the same policy. “UID” is not one universal numbering scheme: a Linux user ID, an Android identity interval, and an IEEE EUI block identify different things.
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Linux UID ranges for accounts
What the historical LSB specification says
The Linux Standard Base 2.0.1 specifies that “the system UIDs from 0 to 99 should be statically allocated by the system, and shall not be created by applications.” It also reserves UIDs 100–499 for dynamic allocation by system administrators and post-installation scripts using useradd. These figures come from the LSB 2.0.1 specification, not from a current survey or a universal rule: Linux Foundation LSB 2.0.1 UID-range guidance.
| UID interval | LSB 2.0.1 treatment | Important qualification |
|---|---|---|
| 0–99 | Statically allocated system UIDs | Applications should not create IDs in this interval |
| 100–499 | Reserved for dynamic allocation by administrators and post-install scripts using useradd |
Historical specification guidance; current distributions may use different defaults |
Are those values safe on every Linux distribution?
No. The LSB values are historical, and distributions have changed their account-allocation policies over time. Treat them as specification context rather than a universal configuration recipe. Before creating local users or service accounts, check the exact distribution and release documentation and the existing allocation policy on every system involved.
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UID ranges in centralized Linux identity management
In Red Hat Enterprise Linux 8 Identity Management (IdM), an ID range is the valid UID/GID space assigned to users, hosts, and groups in an IdM topology. Range assignment is used to avoid identifier conflicts and to provide consistent IDs across clients. This is RHEL 8 IdM guidance, not a promise that every Linux environment uses the same mechanism: Red Hat Enterprise Linux 8 identity-management planning.
How to plan a range across systems
- Define the scope that must be unique: one host, a group of servers, or the entire identity-management topology.
- Assign non-overlapping ranges to authorities or domains that can create users and groups.
- Keep the mapping consistent on clients so the same account resolves to the same numeric ID.
- Check existing local and directory IDs before introducing a new range; an overlap can make two different accounts appear to be the same owner to the operating system.
- Document the distribution and identity-management version, because range behavior is version- and implementation-specific.
What an Android UID range means
Android uses UID ranges in implementation-specific code as well as for app and user identity concepts. In Android 15.0.0_r23, the netd range parser accepts either a single UID or a start-stop interval, rejects a reversed interval, and considers two ranges overlapping when they share any UID. Those are behaviors of Android’s network-daemon implementation, not Linux account-allocation policy: Android 15.0.0_r23 UidRanges.cpp.
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Android range checks in practice
- Single value: one UID is represented as a one-element range.
- Interval: a start and stop value define the inclusive span handled by the parser.
- Reversed input: a start greater than the stop is rejected.
- Overlap: any shared UID means the two ranges overlap.
Do not apply Android’s parser rules to Linux user creation, or assume that an Android app UID corresponds to a conventional Linux service-account allocation plan.
UID ranges versus IEEE EUI blocks
IEEE also defines contiguous identifier blocks, but these are EUI identifiers rather than Linux or Android user IDs. IEEE guidance describes MA-L, MA-M, and MA-S assignments as different block sizes for EUI identifiers. They identify organizations or devices in IEEE’s identifier system and should not be used to answer a Linux UID-allocation question: IEEE guidelines for EUI, OUI, and CID identifiers.
| Context | What the UID or range identifies | Who controls allocation | How to interpret uniqueness |
|---|---|---|---|
| Linux accounts | User or service accounts represented by numeric UIDs | Distribution defaults, local administrators, or an identity service | Must be unique wherever file ownership and account identity are expected to be consistent |
Android netd |
UID identities used in network-policy range handling | Android platform implementation and callers | Ranges overlap when they share any UID |
| IEEE EUI | IEEE-assigned device or organizational identifier blocks | IEEE assignment rules | Separate from operating-system user-ID namespaces |
How to avoid UID conflicts
- Identify the namespace first. Confirm whether the numbers belong to Linux accounts, Android policy code, or IEEE EUI identifiers.
- Set the required uniqueness boundary. A local-only server, a fleet of Linux clients, and an IdM topology have different conflict scopes.
- Use documented ranges for the exact release. Do not promote the LSB 2.0.1 intervals into current universal defaults.
- Reserve non-overlapping space. Separate local, directory, service, and externally managed allocations so two authorities cannot issue the same ID.
- Audit before migration. Compare existing numeric IDs and ownership mappings before changing a range; changing a number without remapping file ownership can leave data owned by an unintended account.
- Record the policy. Keep the range boundaries, allocator, release, and exception list with your system documentation.
Choosing a range for system users
There is no single answer that is correct for every Linux installation. For a standalone host, follow that distribution’s current system-account policy and avoid IDs already in use. For centrally managed Linux systems, use the identity service’s documented non-overlapping ranges and make the range large enough for the accounts that authority is expected to create. If compatibility with an older specification matters, record that the 0–99 and 100–499 guidance comes specifically from LSB 2.0.1.
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