Wiki source code of Commands

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

version	line-number	content
1.1	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
2.1	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
3.1	24	(% class="box warningmessage" %)
2.1	25	(((
3.1	26	Use dd command with caution as it can cause severe dammage to the system
2.1	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
3.1	39	{{code language="shell"}}
	40	dd if=/dev/zero of=/tmp/test2.img bs=512 count=1000 oflag=dsync
2.1	41	1000+0 records in
	42	1000+0 records out
3.1	43	512000 bytes (512 kB, 500 KiB) copied, 1.22846 s, 417 kB/s
	44	{{/code}}