If the system has been corrupted, and there is no grub menu, then boot from a live CD, open a terminal and do this:

sudo fdisk -l # find the root filesystem
sudo mount /dev/sda2 /mnt #whatever your root filesystem is
D1=dev
D2=dev/pts
D3=proc
D4=sys
sudo mount --bind /$D1 /mnt/$D1 &&
sudo mount --bind /$D2 /mnt/$D2 &&
sudo mount --bind /$D3 /mnt/$D3 &&
sudo mount --bind /$D4 /mnt/$D4

sudo chroot /mnt # You are now back in the main hard drive

cd /etc/default
cp grub grub.orig
vi grub
# change timeout from 0 to 10
# change STYLE from hidden to menu
# remove # from Ter

tar -cvjSf filename.tar.bz2 foldername
-c create
-v verboase
-j bzip2
-S Sparse files handled efficiently
-f filename

To securely wipe a hard drive of all data, do:

apt install wipe
shred -vfz -n 2 /dev/sdb

• Options above are verbose, force, zero out in an extra pass
• Number of passes: -n 2

An alternative “light” way of doing this is to simply copy random bytes

D=sdb
fdisk -l /dev/$D # make sure we have the right device
dd if=/dev/urandom of=/dev/$D bs=4096 status=progress

• If the progress info is not sufficient, then from another terminal session do the following and updates will appear in the original terminal

pgrep -l '^dd$'   # gives the pid: nnnn DD
watch -n 60 kill

See user manual here: www.gnu.org/…escue_manual.html

• Install with apt install gddrescue

Example script:

• /dev/sdc is the bad drive which is being recovered to /dev/sdb

# first pass to copy the good sectors and make a log file of the bad
ddrescue -n /dev/sdc /dev/sdb logfile
# second pass keeps retrying the bad sectors
ddrescue -dr3 /dev/sdc /dev/sdb logfile

# have a look at what we have and do some validation
fdisk /dev/sdb
e2fsck -v -f /dev/sdb1
e2fsck -v -f /dev/sdb2

# It might be necessary to manually copy partition

• List current tables with line numbers and stats

iptables -L INPUT --line-numbers -v

• Append another rule

iptables -A INPUT -s 58.245.23.126/24 -j DROP

• Delete rule #3

iptables -D INPUT 3

• The moment you apply IPTABLE rule it immediately becomes active.But it will not survive a reboot.
• To be able to survive IPTABLES a reboot in your network configuration file /etc/network/interfaces file (referring to a Debian/Ubuntu system) you need to add:

pre-up  iptables-restore < firewall.txt

Making changes persistent in CentOS 5

iptables rules are stored in memory.

Undeleting a file is not easy in Linux.
However, if it's a text file, and you know a phrase from it, you can search the whole drive for the contents:
```
grep -a -C 200 -F "words in file" /dev/hda1 | more #change /dev/hda1 to whatever is appropriate
```

Make sure userid’s and groupid’s match between the systems

• e.g. usermod -u 1001 -g 504 -c "Andrew Fountain" andrewf

Set up the server

• set up the fully qualified domain name, e.g.

using smartmontools documentation, try:

smartctl -d sat,16 -i /dev/sdc # find if enabled
smartctl -d sat,16 -a /dev/sdc # display all info

more documentation:

• www.smartmontools.org/…tl.8.in
• www.cyberciti.biz/…ailing.html
• it.toolbox.com/…ng-to-do-31523

I you get “device is busy” when running umount, try

sudo lsof | grep /dev/xxxx
# or
sudo fuser -cu /dev/xxxx