Databases, Systems & Networks

Source: nixCraft

I‘m a new Unix system user. How do I use sudo command without a password on a Linux or Unix-like systems?

Some times you may need to run a command with root privileges, but you do not want to type a password using sudo command. This is useful for scripting or any other purpose. This can be achieved by editing /etc/sudoers file and setting up correct entries.

You need to consider any security consequence of allowing a sudo command execute without a password. Lire la suite…

Here is what happens:

$ sudo visudo
>>> /etc/sudoers: syntax error near line 28 <<<
sudo: parse error in /etc/sudoers near line 28
sudo: no valid sudoers sources found, quitting

On a modern Ubuntu system (and many other GNU/Linux distributions), fixing a corrupted sudoers file is actually quite easy, and doesn’t require rebooting, using a live CD, or physical access to the machine.

To do this via SSH, log in to the machine and run the command pkexec visudo. If you have physical access to the machine, SSH is unnecessary; just open a Terminal window and run that pkexec command. Lire la suite…

Bash Shell Loop

How do I run shell loop over set of files stored in a current directory or specified directory?

You can use for loop easily over a set of shell file under bash or any other UNIX shell using wild card character.

Syntax

The general syntax is as follows:

for f in file1 file2 file3 file5
do
 echo "Processing $f"
 # do something on $f
done

You can also use shell variables:

FILES="file1
/path/to/file2
/etc/resolv.conf"
for f in $FILES
do
	echo "Processing $f"
done

You can loop through all files such as *.c, enter:

$ for f in *.c; do echo "Processing $f file.."; done

Lire la suite…

find -not -empty -type f -printf "%s\n" | sort -rn | uniq -d | xargs -I{} -n1 find -type f -size {}c -print0 | xargs -0 md5sum | sort | uniq -w32 --all-repeated=separate

find -type f -exec md5sum '{}' ';' | sort | uniq --all-repeated=separate -w 33 | cut -c 35-

find -type d -name ".svn" -prune -o -not -empty -type f -printf "%s\n" | sort -rn | uniq -d | xargs -I{} -n1 find -type d -name ".svn" -prune -o -type f -size {}c -print0 | xargs -0 md5sum | sort | uniq -w32 --all-repeated=separate

find -not -empty -type f -printf "%-30s'\t\"%h/%f\"\n" | sort -rn -t$'\t' | uniq -w30 -D | cut -f 2 -d $'\t' | xargs md5sum | sort | uniq -w32 --all-repeated=separate

find . -type f -exec md5 '{}' ';' | sort | uniq -f 3 -d | sed -e "s/.*(\(.*\)).*/\1/"

# Modify this file accordingly for your specific requirement.
# http://www.thegeekstuff.com
# 1. Delete all existing rules
iptables -F

# 2. Set default chain policies
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT DROP

# 3. Block a specific ip-address
#BLOCK_THIS_IP="x.x.x.x"
#iptables -A INPUT -s "$BLOCK_THIS_IP" -j DROP
 Lire la suite...