Unix – Silico Sciences

‘undo’ ssh-add

List all available keys.

$ ssh-add -l 4096 ... training@silico_rsa (RSA) 2048 ... alex@A010-PC10 (RSA) [..]

1
2
3
4

$ ssh-add -l
4096 ... training@silico_rsa (RSA)
2048 ... alex@A010-PC10 (RSA)
[..]
Remove a key.

$ ssh-add -D training@silico_rsa

1

$ ssh-add -D training@silico_rsa
List all available keys.

$ ssh-add -l 2048 ... alex@A010-PC10 (RSA) [..]

1
2
3

$ ssh-add -l
2048 ... alex@A010-PC10 (RSA)
[..]

remove a user and all corresponding files

deluser --remove-home --remove-all-files <username>

1	deluser --remove-home --remove-all-files <username>

If you want to keep a user’s files, use

userdel <username>

1	userdel <username>

MySQL won’t start automatically during system startup

P: The MySQL service does not automatically start during system startup.
A:
1. Purge and redo startup scripts:
  
  sudo update-rc.d -f mysql remove sudo update-rc.d mysql defaults
  
  1
  2
  
  sudo update-rc.d -f mysql remove
  sudo update-rc.d mysql defaults
2. Change bind-address to 0.0.0.0:
  
  sudo nano /etc/mysql/my.cnf
  
  1
  
  sudo nano /etc/mysql/my.cnf
  
  Find bind-address = 127.0.0.1 and change it to bind-address = 0.0.0.0
3. Check /etc/init/mysql.override: This file might override your startup settings. In case it looks like this
```
$ less /etc/init/mysql.override
manual
```
  Execute the following:
  
  echo auto | sudo tee /etc/init/mysql.override
  
  1
  
  echo auto | sudo tee /etc/init/mysql.override
4. Done.

change file encoding recursively

Good:

find . -name "*.java" -exec iconv -f windows-1252 -t utf-8 {} -o {}.utf8 \;

1	find . -name "*.java" -exec iconv -f windows-1252 -t utf-8 {} -o {}.utf8 \;

Bad:

find . -name "*.java" -exec iconv -f windows-1252 -t utf-8 {} -o converted/{} \;

1	find . -name "*.java" -exec iconv -f windows-1252 -t utf-8 {} -o converted/{} \;

The second one will only work if find will not descend into sub directories, since the directory tree inside of converted will not be created on demand, as it would be the case e.g. for mkdir -p. The result will be a ‘file or directory not found’ error.

mv: do not override destination file that is newer than source file (update move)

mv does not support the update option, unlike rsync and cp. If your version of coreutils does support it, using cp (followed by rm) is the easiest way to perform an update move operation:

$ cp -avu * [destination]
$ rm -rf *

1 2	$ cp -avu * [destination] $ rm -rf *

kill all processes by user

pkill -u username

1	pkill -u username

Install Oracle Java 8

$ sudo add-apt-repository ppa:webupd8team/java
$ sudo apt-get update
$ sudo apt-get install oracle-java8-installer
$ java -version
java version "1.8.0_72"
Java(TM) SE Runtime Environment (build 1.8.0_72-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.72-b15, mixed mode)
$ javac -version
javac 1.8.0_72

$ sudo add-apt-repository ppa:webupd8team/java

$ sudo apt-get update

$ sudo apt-get install oracle-java8-installer

$ java -version

java version "1.8.0_72"

Java(TM) SE Runtime Environment (build 1.8.0_72-b15)

Java HotSpot(TM) 64-Bit Server VM (build 25.72-b15, mixed mode)

$ javac -version

javac 1.8.0_72

count words in a PDF file

Shell

pdftotext mypdf.pdf - | tr -d '.' | wc -w

1

pdftotext mypdf.pdf - | tr -d '.' | wc -w
Shell

pdftops mypdf.pdf ps2ascii mypdf.ps | tr -d '.' | wc -w

1
2

pdftops mypdf.pdf
ps2ascii mypdf.ps | tr -d '.' | wc -w

Exemplary output:

pdftotext mypdf.pdf - | tr -d '.' | wc -w
40730
pdftops mypdf.pdf
ps2ascii mypdf.ps | tr -d '.' | wc -w
33088

pdftotext mypdf.pdf - | tr -d '.' | wc -w

40730

pdftops mypdf.pdf

ps2ascii mypdf.ps | tr -d '.' | wc -w

33088

tr -d '.' removes single dots (such as from the TOC).

phpMyAdmin Change default URL

sudo nano /etc/apache2/conf.d/apache.conf

1	sudo nano /etc/apache2/conf.d/apache.conf

Change

Alias /phpmyadmin /usr/share/phpmyadmin

Alias /my-secret-url /usr/share/phpmyadmin

reload config

sudo service apache2 reload

1	sudo service apache2 reload

gzip all files in a directory

$ for f in $(ls -1); do gzip $f; done;

1	$ for f in $(ls -1); do gzip $f; done;