Wiki source code of Commands

Last modified by Julien Fleury on 2021/02/02 19:05

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		1	{{box cssClass="floatinginfobox" title="Contents"}}
		2	{{toc/}}
		3	{{/box}}
		4
		5	= Useful Linux commands =
		6
		7	Here is a list of useful commands to be executed on a Linux server (debian). Feel free to contribute by feeding this page with your own tricks and tips.
		8
		9	== Telnet like ==
		10
		11	It is often required to test if a host[:port] is reachable and access is granted from a server. Best way to execute a telnet like command on a Linux console is to work with special files used to communcate with peripherals. Thus, in order to test tcp port 8000 on server 10.100.100.100, simply try to write in file /dev/tcp/10.100.100.100/8000 and add a return value depending on success or failure
		12
		13	{{code language="shell"}}
		14	echo > /dev/tcp/10.100.100.100/8000 && echo 'up' \|\| echo 'down'
		15	-bash: connect: Connection refused
		16	-bash: /dev/tcp/10.100.100.100/8000: Connection refused
		17	down
		18	{{/code}}
		19
		20	== Test disk speed ==
		21
		22	dd command allows to copy all or parts of a disk by bytes block without impact from content structure of the disk.
		23
		24	(% class="box warningmessage" %)
		25	(((
		26	Use dd command with caution as it can cause severe dammage to the system
		27	Do not use dd to duplicate a disk. Prefer ddrescue command
		28	)))
		29
		30	Command structure
		31
		32	(% class="box" %)
		33	(((
		34	dd if=<source> of=<target> bs=<block size> count=<number of blocks> oflag=<flag>
		35	)))
		36
		37	oflag: 'dsync' to use synchronized I/O for data
		38
		39	{{code language="shell"}}
		40	dd if=/dev/zero of=/tmp/test2.img bs=512 count=1000 oflag=dsync
		41	1000+0 records in
		42	1000+0 records out
		43	512000 bytes (512 kB, 500 KiB) copied, 1.22846 s, 417 kB/s
		44	{{/code}}