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Get all possible problems from any log files
Using the grep command, retrieve all lines from any log files in /var/log/ that have one of the problem states

deaggregate ip ranges
Taking file with ip ranges, each on it's own line like: $cat ipranges.txt 213.87.86.160-213.87.86.193 213.87.87.0-213.87.88.255 91.135.210.0-91.135.210.255 command returns deaggregated ip ranges using ipcalc deaggregate feature like that: 213.87.86.160/27 213.87.86.192/31 213.87.87.0/24 213.87.88.0/24 91.135.210.0/24 Useful for configuring nginx geo module

Temporarily ignore mismatched SSH host key
This command will bypass checking the host key of the target server against the local known_hosts file. When you SSH to a server whose host key does not match the one stored in your local machine's known_hosts file, you'll get a error like " WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!" that indicates a key mismatch. If you know the key has legitimately changed (like the server was reinstalled), a permanent solution is to remove the stored key for that server in known_hosts. However, there are some occasions where you may not want to make the permanent change. For example, you've done some port-forwarding trickery with ssh -R or ssh -L, and are doing ssh user@localhost to connect over the port-forwarding to some other machine (not actually your localhost). Since this is usually temporary, you probably don't want to change the known_hosts file. This command is useful for those situations. Credit: Command found at http://linuxcommando.blogspot.com/2008/10/how-to-disable-ssh-host-key-checking.html. Further discussion of how it works is there also. Note this is a bit different than command #5307 - with that one you will still be prompted to store the unrecognized key, whereas this one won't prompt you for the key at all.

After typing lots of commands in windows, save them to a batch file quickly
After typing the command below, you will be greeted with nothing. press the up arrow to find the previous command you typed, press enter. repeat this as many times as you need, then hit CTRL-Z and press enter to save to the 'batchfilename.bat' file.

look for a function reference in a library set

Create new user with home dir and given password
The crypt function takes a password, key, as a string, and a salt character array which is described below, and returns a printable ASCII string which starts with another salt. It is believed that, given the output of the function, the best way to find a key that will produce that output is to guess values of key until the original value of key is found. from http://en.wikipedia.org/wiki/Crypt_(Unix)

delete files containing matching text
-r recursively -Z zero byte after each file name instead of the usual newline -l only filenames

Find all directories on filesystem containing more than 99MB
Finds all directories containing more than 99MB of files, and prints them in human readable format. The directories sizes do not include their subdirectories, so it is very useful for finding any single directory with a lot of large files.

Batch rename extension of all files in a folder, in the example from .txt to .md

Squish repeated delimiters into one
This can be particularly useful used in conjunction with a following cut command like $echo "hello::::there" | tr -s ':' | cut -d':' -f2 which prints 'there'. Much easier that guessing at -f values for cut. I know 'tr -s' is used in lots of commands here already but I just figured out the -s flag and thought it deserved to be highlighted :)


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