Answer:

Just one command needed:

# tr '[:upper:]' '[:lower:]' < input.txt

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Answer:

If you have opened a port using the ufw command in Ubuntu, but now you want to delete it, you can..

# sudo ufw delete allow 8080/tcp

And then do a reload

# # sudo ufw reload

That's all.

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Answer:

With the powerful ImageMagick program, we can easily handle common graphics tasks using command only.

For example, to combine multiple images into a single image, we need just one command:

# convert file1.jpg file2.jpg file3.jpg +append -quality 90 'output.jpg'

The above command (file1.jpg file2.jpg file3.jpg) into the file output.jpg with quality set to 90.

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Answer:

To remove queued message in your Postfix server, you should always check the queue listing first.

When you have confirmed, then you can do

1. Remove specific message based on Queue ID (You can find the ID via postqueue command)

# sudo postsuper -d Queue_ID

2. Remove all messages

# sudo postsuper -d ALL

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2. Debug and verify Postfix configurations
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Answer:

You can simulate a HTTP form post, with a file being uploaded to a remote server using the curl command.

curl -F 'photo=@/upload/image.jpg' http://example.com/upload.php

Assume the name of the form element of your upload is called "photo"

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Answer:

If you have a remote file and you can have a quick edit, if you use the following command:

# ssh -t john@remote-server vim /data/test.txt

You will be prompted to login if you don't have proper ssh key in the remote server, and after finishing editing the file, you will quit the ssh session automatically.

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Answer:

Sometimes we might need to delete files and don't want it can be recovered.

To do so, use the shred command.

# shred -v -n 10 -u -z test.txt

The above command will overwrite the file 10 times before deleting it.

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Answer:

To import files and directories into a SVN repository, you can use the svn import command.

E.g.

Import all files and directories under the current working directory "project1" to a local SVN repository

# cd /data/project1
svn import file:///data/svn/project1

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Answer:

To create a SVN Repository on local drive, you can use the following command:

# cd /data/
# svnadmin create svn

Now you have created a SVN repository located at file:///data/svn/

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Answer:

To create a swap partition using LVM, you just need a few commands!

1. Create a 1G swap partition

# lvcreate -L 1G -n /dev/vg0/swap0

2. Set up a Linux swap partition

# mkswap /dev/vg0/swap0

3. Enable it

# swapon -s /dev/vg0/swap0

You might also want to put the settings in the /etc/fstab, so it will be mounted automatically when your system boot next time.

# sudo vi /etc/fstab

/dev/vg0/swap0       none            swap     sw              0       0

Save and restart your system to test if it is working when system reboot.

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