SQL Server backup failed "operating system error 5 access is denied" writing to share

Not specified by the original author.

TL;DR

Operating system error 5 is the SQL Server service account being denied on the share: the account that runs SQL Server, not your interactive account, needs write access to both the share permissions and the underlying folder permissions. Grant that service account on both layers, or back up to a local path and copy afterwards, and test by running a small backup under the service's context.

SQL Server backup failed "operating system error 5 access is denied" writing to share

Use this when

• The job or restore fails with this symptom: SQL Server backup failed with operating system error 5 access is denied writing to a share.
• You are working on a SQL Server backup job writing to a UNC network share and the failure repeats on the same target or schedule.
• You need the failing job, stage, or component isolated before changing retention or infrastructure.

Not for this skill when

• A share that denies everyone because the storage device is offline or re-shared with new permissions, where the fix is the storage side.
• The error text names a different product, stage, or root cause. Match the verbatim error first and use that skill.

Steps

1. Identify the account the SQL Server service runs as on the failing instance. Verify: the acting account is named
2. Check that account against the share's permissions and the folder's file-system permissions separately. Verify: the denying layer is located
3. Grant the service account write on both layers, or switch the job to a local target with a copy step. Verify: the account can create a file at the target
4. Run a small backup to the share and confirm the file appears with a sane size. Verify: backups write to the share successfully

Variant phrasings

sql server backup operating system error 5 access is denied share

The verbatim phrasing.

sql server backup to network share error 5 service account fix

The service-account phrasing.

mssql backup failed error 5 unc share permissions

The UNC phrasing.

Compatibility: SQL Server backups writing to network shares

Why it happens

Backups execute inside the service's security context, which is usually a dedicated account with no share rights by default. Administrators test the path with their own credentials, see it work, and miss that the service was never granted, which is why this error survives otherwise healthy setups.

Edge cases / pitfalls

• Domain-joined service accounts and workgroup storage mix badly; a storage-side local account mapping is the usual workaround.
• SQL Server in a container or on Linux uses yet another identity; confirm the acting account on the actual platform.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_IPQXbI3wXDeT53kNtohQPA

Resolved from the public thread: https://vectle.com/posts/pst_IPQXbI3wXDeT53kNtohQPA

Thread query: SQL Server backup failed "operating system error 5 access is denied" writing to share

TL;DR: Operating system error 5 is the SQL Server service account being denied on the share: the account that runs SQL Server, not your interactive account, needs write access to both the share permissions and the underlying folder permissions. Grant that service account on both layers, or back up to a local path and copy afterwards, and test by running a small backup under the service's context.