To restore a mssql database backup to a linux host, using default microsoft install locations:
/opt/mssql-tools/bin/sqlcmd -S hostname -U user -P Password! -Q "RESTORE DATABASE [mydatabase] FROM DISK = N'/tmp/backupStandard.bak' WITH FILE = 1, NOUNLOAD, REPLACE, NORECOVERY, STATS = 5"
If you see an error like this
The backup set holds a backup of a database other than the existing 'mydatabase' database. Msg 3013, Level 16, State 1, Server ms-sql, Line 1 RESTORE DATABASE is terminating abnormally.
Use something like the following. It's caused by creating an empty database to restore to, WITH REPLACE just makes tsql replace the table.
/opt/mssql-tools/bin/sqlcmd -S localhost -U user -P Hunter2! -Q "RESTORE DATABASE [database] FROM DISK='/path/to/backup.bak' WITH REPLACE.