Cross-Platform Windows/Linux Considerations, Collations, Agents, External Dependencies, and Tooling

Learning outcomes

A Windows-to-Linux SQL Server move can restore the same user database and still fail operationally because the database is only one layer of the system. Paths, service control, authentication, Agent subsystems, linked-server providers, CLR permissions, FILESTREAM, external scripts, certificates and third-party tooling are platform dependencies. ServiceHub therefore treats cross-platform migration as a feature-parity and operations migration, not “copy the .bak and we are done.”

1. Start with evidence about the current host

SELECT    h.host_platform,    h.host_distribution,    h.host_release,    SERVERPROPERTY('ProductVersion') AS product_version,    SERVERPROPERTY('Collation') AS server_collation,    SERVERPROPERTY('InstanceDefaultDataPath') AS default_data_path,    SERVERPROPERTY('InstanceDefaultLogPath') AS default_log_path,    SERVERPROPERTY('InstanceDefaultBackupPath') AS default_backup_pathFROM sys.dm_os_host_info AS h;USE ServiceHubUpgradeLab;SELECT name, physical_name, type_descFROM sys.database_files;SELECT DATABASEPROPERTYEX(DB_NAME(),'Collation') AS database_collation;

Windows paths such as D:\SQLData\ServiceHub.mdf are not Linux paths. Restore with MOVE and target-approved locations. A database collation can move across platforms, but filesystem semantics and external scripts can still be case-sensitive. Do not infer application correctness from a successful restore.

2. Inventory dependencies that are platform-sensitive

SELECT name, enabled FROM msdb.dbo.sysjobs ORDER BY name;SELECT j.name AS job_name, s.step_id, s.subsystem, s.commandFROM msdb.dbo.sysjobsteps AS sJOIN msdb.dbo.sysjobs AS j ON j.job_id=s.job_idORDER BY j.name,s.step_id;SELECT name, permission_set_desc, is_user_definedFROM sys.assembliesWHERE is_user_defined=1;SELECT name, product, provider, data_sourceFROM sys.serversWHERE server_id<>0;USE ServiceHubUpgradeLab;SELECT name, type_desc FROM sys.database_scoped_credentials;SELECT name, type_desc, data_source FROM sys.external_data_sources;SELECT name, thumbprint, expiry_date FROM sys.certificates WHERE name NOT LIKE '##%';

On SQL Server 2025 Linux, current Microsoft documentation lists several gaps that matter to migration: merge replication is unavailable; linked servers to non-SQL Server third-party sources are unavailable (PolyBase can be an alternative in suitable cases); FILESTREAM/FileTable are unavailable; CLR assemblies requiring EXTERNAL_ACCESS or UNSAFE are unavailable; SQL Server Agent does not support the Windows-style CmdExec/PowerShell/Queue Reader/SSIS/SSAS/SSRS subsystems and Agent alerts are unavailable. SQL Server Browser is also unnecessary because Linux supports a single default instance per host and the port is explicitly configured.

3. Authentication, certificates and external services do not migrate themselves

Windows authentication can be integrated with Active Directory on Linux, but the setup and service identity are different from merely copying Windows logins. Availability Group endpoints on Linux use certificate-based authentication rather than Windows integrated authentication. TDE/backup-encryption protectors, database master keys, linked-server credentials and application TLS trust all need explicit target handling.

SELECT name, type_desc, is_disabled, sidFROM sys.server_principalsWHERE type IN ('S','U','G') AND name NOT LIKE '##%';SELECT name, credential_identityFROM sys.credentials;USE ServiceHubUpgradeLab;SELECT name, thumbprint, pvt_key_encryption_type_descFROM sys.certificatesWHERE name NOT LIKE '##%';SELECT name, is_master_key_encrypted_by_serverFROM sys.databasesWHERE name=N'ServiceHubUpgradeLab';

4. Deliberately wrong: “same engine, therefore feature parity”

The core Database Engine is shared, but platform support is not identical. A Windows job step that shells out to PowerShell, an UNSAFE CLR assembly, FILESTREAM document storage or a third-party OLE DB linked server can be business-critical even though the relational tables restore perfectly. The repair is to classify every dependency: supported unchanged, supported with reconfiguration, replace, or block migration.

USE ServiceHubUpgradeLab;GOIF OBJECT_ID(N'lab24.PlatformReadiness',N'U') IS NULLCREATE TABLE lab24.PlatformReadiness(    dependency_name nvarchar(200) NOT NULL PRIMARY KEY,    dependency_type varchar(40) NOT NULL,    target_status varchar(24) NOT NULL,    remediation nvarchar(600) NULL,    evidence_uri nvarchar(500) NULL,    checked_at datetime2(0) NOT NULL DEFAULT SYSUTCDATETIME());UPDATE lab24.PlatformReadinessSET dependency_type=N'Agent subsystem',target_status=N'REPLACE',    remediation=N'Use an external scheduler/automation path or supported Linux job design.',checked_at=SYSUTCDATETIME()WHERE dependency_name=N'Agent PowerShell step';IF @@ROWCOUNT=0 INSERT lab24.PlatformReadiness(dependency_name,dependency_type,target_status,remediation)VALUES(N'Agent PowerShell step',N'Agent subsystem',N'REPLACE',N'Use an external scheduler/automation path or supported Linux job design.');UPDATE lab24.PlatformReadinessSET dependency_type=N'Certificate/key',target_status=N'RECONFIGURE',    remediation=N'Transfer certificate/private key securely before restore.',checked_at=SYSUTCDATETIME()WHERE dependency_name=N'TDE protector';IF @@ROWCOUNT=0 INSERT lab24.PlatformReadiness(dependency_name,dependency_type,target_status,remediation)VALUES(N'TDE protector',N'Certificate/key',N'RECONFIGURE',N'Transfer certificate/private key securely before restore.');UPDATE lab24.PlatformReadinessSET dependency_type=N'Database setting',target_status=N'VALIDATE',    remediation=N'Test comparisons plus application/filesystem assumptions on target.',checked_at=SYSUTCDATETIME()WHERE dependency_name=N'Database collation';IF @@ROWCOUNT=0 INSERT lab24.PlatformReadiness(dependency_name,dependency_type,target_status,remediation)VALUES(N'Database collation',N'Database setting',N'VALIDATE',N'Test comparisons plus application/filesystem assumptions on target.');

The readiness table is deliberately not an auto-remediation engine. It is evidence that each dependency has an owner and disposition.

5. Production judgment

Cross-platform migration is attractive when Linux operational standards, container/VM platforms or cost models justify it, but the database must be assessed together with the surrounding instance and application ecosystem. Use current SSMS migration assessment feature parity, current Linux supported-feature documentation, a restored target rehearsal and representative application tests. Keep unsupported dependencies visible rather than silently dropping them during migration.

Authoritative references

• Editions and supported features: SQL Server 2025 on Linux
• SQL Server on Linux FAQ
• SQL Server 2025 Linux release notes
• Upgrade SQL Server using SSMS migration component
• Active Directory authentication on SQL Server Linux