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Use tagged vlans
Great for sysadmins! Don't forget to pass the vlan to your port in a manageable switch. After vconfig, you should use $sudo ifconfig eth0.[VID] up Now the interface is up, you can use dhclient or ifconfig again to get an ip address.

sort the output of the 'du' command by largest first, using human readable output.
In this case I'm just grabbing the next level of subdirectories (and same level regular files) with the --max-depth=1 flag. leaving out that flag will just give you finer resolution. Note that you have to use the -h switch with both 'du' and with 'sort.'

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

run remote linux desktop
First of all you need to run this command. X :12.0 vt12 2>&1 >/dev/null & This command will open a X session on 12th console. And it will show you blank screen. Now press Alt + Ctrl + F7. You will get your original screen. Now run given command "xterm -display :12.0 -e ssh -X user@remotesystem &". After this press Alt + Ctrl + F12. You will get a screen which will ask you for password for remote linux system. And after it you are done. You can open any window based application of remote system on your desktop. Press Alt + Ctrl + F7 for getting original screen.

Creates a 'path' command that always prints the full path to any file
The command creates an alias called 'path', so it's useful to add it to your .profile or .bash_profile. The path command then prints the full path of any file, directory, or list of files given. Soft links will be resolved to their true location. This is especially useful if you use scp often to copy files across systems. Now rather then using pwd to get a directory, and then doing a separate cut and paste to get a file's name, you can just type 'path file' and get the full path in one operation.

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

How to stop MAC Address via IPTables
edit the /etc/sysconfig/iptables file and try to work whit this: -A INPUT -i (interface) -m mac (mac address) -j ACCEPT/DROP

for all who don't have the watch command
#Usage: watch timeinsecond "command"

Unzip and untar a *.tar.gz file in one go to a specific directory
A *.tar.gz file needs to be unzipped & then untarred. Previously I might have unzipped first with $gunzip -d file.tar.gz and then untarred the result with $tar -xvf file.tar (Options are extract, verbose, file) Using the -z (decompress) option on tar avoids the use of gzip (or gunzip) first. Additionally the -C option will specify the directory to extract to.


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