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Multiplication table
The multiplication table for math study

List only directory names
This command would be useful when it is desirable to list only the directories. Other options Hidden directory $ ls -d .*/ Other path $ ls -d /path/to/top/directory/.*/ Long format: $ ls -ld */

Kick user

Sort lines on clipboard
Does the same thing in environments where you have "xclip" instead of "pbpaste"/"pbpate" and "pbcopy".

list block devices
Shows all block devices in a tree with descruptions of what they are.

prevent accidents and test your command with echo
if you're using wildcards * or ? in your command, and if you're deleting, moving multiple files, it's always safe to see how those wildcards will expand. if you put "echo" in front of your command, the expanded form of your command will be printed. It's better safe than sorry.

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

Migrate existing Ext3 filesystems to Ext4
Before doing this, back-up all data on any ext3 partitions that are to be converted to ext4. After running previous command you MUST run fsck, is needed to return the filesystem to a consistent state. $ fsck -pDf /dev/yourpartition Edit /etc/fstab and change the 'type' from ext3 to ext4 for any partitions that are converted to ext4.

Create an alias, store it in ~/.bash_aliases and source your new alias into the ~/.bashrc
This is useful if you use a shell with a lot of other users. You will be able to run "topu" to see your running processes instead of the complete 'top -u username'. Read more on alias: http://man.cx/alias

Poor man's ntpdate
If you don't have netcat, you can use curl.


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