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back ssh from firewalled hosts
host B (you) redirects a modem port (62220) to his local ssh. host A is a remote machine (the ones that issues the ssh cmd). once connected port 5497 is in listening mode on host B. host B just do a ssh 127.0.0.1 -p 5497 -l user and reaches the remote host'ssh. This can be used also for vnc and so on.

positions the mysql slave at a specific master position
say you want to reinitialize the slave database without resetting the master positions. You stop the slave, dump the master database with --master-data=2 then execute the command on the slave and wait for it to stop at the exact position of the dump. reinit the slave db and start the slave. enjoy.

mtr, better than traceroute and ping combined
mtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool. As mtr starts, it investigates the network connection between the host mtr runs on and HOSTNAME. by sending packets with purposly low TTLs. It continues to send packets with low TTL, noting the response time of the intervening routers. This allows mtr to print the response percentage and response times of the internet route to HOSTNAME. A sudden increase in packetloss or response time is often an indication of a bad (or simply over‐loaded) link.

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

ssh autocomplete
Add to your bash profile to minimize carpal tunnel syndrome. Doesn't work with user@hostname but appending "-l user" works fine if needed. Works for ping as well.. complete -W "$(echo `cat ~/.ssh/known_hosts | cut -f 1 -d ' ' | sed -e s/,.*//g | uniq | grep -v "\["`;)" ping

calculate in commandline with bash
Only works for integer arithmetic.

removes characters from cursor to the end of line

Find inside files two different patterns in the same line and for matched files show number of matched lines
The option -print0 for find and -0 for grep help prevent issue with weird characters or spaces in filenames. Furthermore with xargs there is no limited number of arguments that find can throw.

a find and replace within text-based files
using find's exec option instead of a for loop and using sed's -i option for inplace replacement. no need to do the file swap.

Set all CPU cores' CPU frequency scaling governor to maximum performance


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