Summary of Linux technical knowledge points

Summary of Linux technical knowledge 1. the system of the existing computing node has crashed and all hard disk partitions cannot be deleted. At this time, you can use any system installation disk to delete the hard disk partition and reformat it, then, you can use the master node to re-distribute the nodes, boot the network, and automatically install the system. 2. coms resends an insert-ethers hostname compute-1-33 node. coms deletes a node. coms remove hostname compute-1-34. coms list all nodes coms list host5. test disk write capacity time dd if =/dev/zero of =/$ user/write. dd bs = 1 M count = 1024 # Because/dev/zero is a pseudo device, it only produces a blank swap stream, so IO is concentrated in write. dd file write operations, so this command is equivalent to testing disk write capacity 6. test disk read capability time dd if =/$ user/write. dd of =/dev/null # Because/$ user/wirte. dd is a physical partition. Read/dev/null is a pseudo device, which is equivalent to a black hole, the IO of this command only occurs in/$ user/write. dd is equivalent to testing the disk's read capacity. test disk read/write capability time dd if/$ user/write. dd of =/$ user/read. dd # Because/$ user/wirte. bb and/$ user/read. both dd and physical partitions generate IO, that is, testing the disk's read/write capability at the same time.