A method for controlling a digital device for performing a booting process, the method comprising: removing duplicate page data from among page data stored in a first memory comprising calculating a hash value on a page-by-page basis for the page data stored in the first memory; and determining whether the calculated hash value is duplicate, wherein, for page data having a duplicate hash value, only location information about the duplicate page data is stored in a mapping table; comparing page data remaining after the removing with page data pre-stored in a second memory; selectively removing the duplicate page data depending on whether the duplicate page data is located in a hot cluster of the second memory as a result of the comparison, wherein based on a number of times of duplicate use of a block obtained in a block use counting operation, the block is designated as a hot block when the number of times of block use that the block has is greater than a first threshold, wherein a number of hot blocks in each cluster including a predetermined number of blocks is checked and compared with a second threshold, wherein when the number of hot blocks present in the checked cluster is greater than the second threshold, the degree of data fragmentation in the cluster is checked, and wherein when the degree of data fragmentation is greater than a third threshold, the cluster is designated as a hot cluster, wherein the selective removing further comprises performing cluster management; and determining whether the page data remaining after the removal of the duplicate page data from among page data stored in the first memory and the page data pre-stored in the second memory overlap through a hash value calculated on the page-by-page basis, wherein, when page data having a duplicate hash value is located in the hot cluster of the second memory, only location information about the duplicate page data is stored in the mapping table, wherein the mapping table is a mapping relationship between logical addresses of the page data stored in the first memory and physical addresses of the page data stored in the second memory; generating a snapshot image based on page data remaining after the selective removing, wherein performing the cluster management comprises updating information on clusters in which the snapshot image is located; storing the generated snapshot image in the second memory; loading the generated snapshot image into the first memory; and restoring the digital device to a system state before shutdown of said digital device based on the page data information about the generated snapshot image. removing duplicate page data from among page data stored in a first memory comprising calculating a hash value on a page-by-page basis for the page data stored in the first memory; and determining whether the calculated hash value is duplicate, wherein, for page data having a duplicate hash value, only location information about the duplicate page data is stored in a mapping table; comparing page data remaining after the removing with page data pre-stored in a second memory; selectively removing the duplicate page data depending on whether the duplicate page data is located in a hot cluster of the second memory as a result of the comparison, wherein based on a number of times of duplicate use of a block obtained in a block use counting operation, the block is designated as a hot block when the number of times of block use that the block has is greater than a first threshold, wherein a number of hot blocks in each cluster including a predetermined number of blocks is checked and compared with a second threshold, wherein when the number of hot blocks present in the checked cluster is greater than the second threshold, the degree of data fragmentation in the cluster is checked, and wherein when the degree of data fragmentation is greater than a third threshold, the cluster is designated as a hot cluster, wherein the selective removing further comprises performing cluster management; and determining whether the page data remaining after the removal of the duplicate page data from among page data stored in the first memory and the page data pre-stored in the second memory overlap through a hash value calculated on the page-by-page basis, wherein, when page data having a duplicate hash value is located in the hot cluster of the second memory, only location information about the duplicate page data is stored in the mapping table, wherein the mapping table is a mapping relationship between logical addresses of the page data stored in the first memory and physical addresses of the page data stored in the second memory; generating a snapshot image based on page data remaining after the selective removing, wherein performing the cluster management comprises updating information on clusters in which the snapshot image is located; storing the generated snapshot image in the second memory; loading the generated snapshot image into the first memory; and restoring the digital device to a system state before shutdown of said digital device based on the page data information about the generated snapshot image.