|A journaling filesystem is a filesystem that maintains a special file called a journal that is used to repair any inconsistencies that occur as the result of an improper shutdown of a computer. Such shutdowns are usually due to an interruption of the power supply or to a software problem that cannot be resolved without a rebooting. A filesystem is a way of storing information on a computer that usually consists of a hierarchy of directories (also referred to as the directory tree) that is used to organize files. Each hard disk drive (HDD) or other storage device as well as each partition (i.e., logically independent section of a HDD) can have a different type of filesystem if desired. Journaling filesystems write metadata (i.e., data about files and directories) into the journal that is flushed to the HDD before each command returns. In the event of a system crash, a given set of updates may have either been fully committed to the filesystem (i.e., written to the HDD), in which case there is no problem, or the updates will have been marked as not yet fully committed, in which case the system will read the journal, which can be rolled up to the most recent point of data consistency.|
# vim ifcfg-enp0s8 ~ write ---------- 'IPADDR' = 192.168.1.34 ~ 'NETMASK'= 255.255.255.0 ~ 'ONBOOT' = yes ~ 'BOOTPROTO'= 'static'
An Ethernet frame must be at least 64 bytes for collision detection to work, and can be a maximum of 1,518 bytes. The packet starts with a preamble that controls the synchronization between sender and receiver and a "Start Frame Delimiter" (SFD) that defines the frame. Both values are bit sequences in the format “10101010 ...” in which the actual frame contains information about source and destination addresses (MAC format), control information (in the case of Ethernet II the type field, later a length specification), followed by the transmitted data record. A frame check sequence (FCS) is an error-detecting code that closes the frame (except for the preamble and SFD). The packet is completed by an "Inter Frame Gap," which defines a 9.6 μs transmission pause.
Ethernet II uses the classic frame structure with a type field ("Type") which defines various protocols of the network layer. In the OSI model, the network layer is important for connecting and providing network addresses. The type field was replaced by a length specification in later frame formats.