Category: Linux

UPDATE: This post has been added at easywebdns : recovering ext3 hard disks

So, here are the tools you need

1- Checking a linux partition for bad sectors / Bad Blocks without deleting the data

badblocks -o /path/somefiletowriteto.txt /dev/sdb1

this will do a check and write the bad block numbers to a text file.

Please note that 6TB and 8TB hard drives will not work out of the box with badblocks program, you will probably get a message informing you that the boundary must fit a 32bit integer (Value too large for defined data type), in that case, you can always increase the block size with the (-b 4096) switch, this will give you 8 times more block addressing space (Since the default is 512 bytes.

If you want it to test the disks hard but you are OK with deleting the data (Say after you dd_rescue), then try the -w switch

badblocks -w -o /path/somefiletowriteto.txt /dev/sdb1

Or, to see information while it scans

badblocks -wsv /dev/sdd > /root/250bad-blocks.txt

Notice that the -w has to come before the -o since the -o must be followed by a file name.

2- fsck /dev/sdb1 , the all famous, need i say more ?

3- tune2fs

tune2fs -O ^has_journal /dev/sdb1

remove the Journal (Converting ext3 to ext2 file system)

4- Mounting a disk: mount -t ext3 /dev/sdb1 /adirectory

5- debugfs <- use it in Read only more, this thing is like brain surgery, 1 mistake and your FS is playing chess in heaven with all the other dead disks

6- dd_rescue /dev/sdb1 /directory/mydisk.img

7- Running fsck on a disk image

fsck -y /path/mydisk.img

8- Mount the image

mount /pathto/backup.img /mountpoint/data

this is a nice link for you http://www.linuxjournal.com/article/193 that already has info about the stuff i mentioned here

Those are probably the most common, will add more when i remember them

This tutorial was first written for Lenny, then tested on squeeze, wheezy… up to bullseye

In August 2021, I have revised this for Debian Buster (10) and Debian Bullseye (11).

If you have installed Debian Lenny with file sharing (in the lenny installer), you will need to add users to that installation and specify folders that need to be shared, here i will show you how to add a user and share a folder with that user.

If you have not installed file sharing while installing Debian lenny, you need to install them, the easiest way to do that is

apt-get install samba

Or if you like

run the command

aptitude

using the arrow keys and the enter key, expand “TASKS” then place the bar over File Server, then the plus sign to select it (Shift +), right after hit “g” then “g” on your keyboard to install them.

Once done, add the following lines to smb.conf

[public]
   comment = Public Folder
   path = /public
   writable = yes
   guest ok = yes
   guest only = yes
   force create mode = 775
   force directory mode = 775
[private]
   comment = Private Folder
   path = /private
   writable = yes
   guest ok = no
   valid users = @smbshare
   force create mode = 770
   force directory mode = 770
   inherit permissions = yes

Now to adding users, from the following 3 commands, After the second and after the third command, you will be asked to chose a password for the user joe

useradd yazeed -m -G users
passwd yazeed
smbpasswd -a yazeed

Now with this out of the way, you can also edit the following fields in the file /etc/samba/smb.conf

The following need to be edited

netbios name : Should become the name of the computer on the network, in windows, this is the machine’s name
hosts allow : If your network is like mine where PCs take IP addresses of the form 192.168.2.x, then this one should be 127. 192.168.2. where 127 is for the local machine, the following part of the IP is the part of the IP that prefixes the IP of all network machines that should be able to access this file server (usually you will change the 2 with a 0 or 1)
interfaces : 127.0.0.1/8 192.168.2.0/24, like above, if your IP subnet is not 192.168.2.x, change it here (usualy you will change the 2 with a 0 or 1)
remote announce : if your subnet does not start with 192.168.2. then change it to your own (usually you will change the 2 with a 0 or 1)
remote browse sync : if your subnet does not start with 192.168.2. then change it to your own (usualy you will change the 2 with a 0 or 1)

Now scroll down, you will see a sample folder, edit that to the folder you want to share, and copy it over and over again for any other folders that you want to share, You are done, now you should be able to open those folders from the network.

My web server got hacked today, i know because my datacenter contacted me today telling me that there is a bruit force attack originating from my server to another server on a different network, so what is happening is that my server got hacked, then the hacker is using the server she hacked to hack other servers by sending FTP requests.

So, how come i got hacked when i am so obsessed with security, well, in reality, this is just an intermediate machine that i used to run a certain script that would move my mail server, and i did not (and did not see the need) to secure it.

What i usually do to secure my server is simply install fail2ban, in this case i did not out of lazyness but here is how i got hacked and how fail2ban would have protected me.

Before i show you the log files, this whole problem would not happen if i had a strong password combined with fail2ban

In the complaining partie’s log files

Tue Jul 24 22:28:27 2012: user: hauvouuc service: ftp target: yyy.yyy.yyy.yyy source: xxx.xxx.xxx.xxx
Tue Jul 24 22:28:27 2012: user: pkmcndgq service: ftp target: yyy.yyy.yyy.yyy source: xxx.xxx.xxx.xxx
Tue Jul 24 22:28:27 2012: user: malumdvc1 service: ftp target: yyy.yyy.yyy.yyy source: xxx.xxx.xxx.xxx

In my log files (auth.log):

Many lines like the following right below each other

Jul 24 18:03:08 run sshd[14229]: pam_unix(sshd:auth): check pass; user unknown
Jul 24 18:03:08 run sshd[14229]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=9.12-14-84.ripe.coltfrance.com 
Jul 24 18:03:10 run sshd[14229]: Failed password for invalid user ts3 from 84.14.12.9 port 41014 ssh2
Jul 24 18:03:11 run sshd[14231]: Invalid user ts3 from 84.14.12.9

Anod some lines like this

Jul 25 15:30:46 run sshd[10728]: pam_unix(sshd:auth): check pass; user unknown
Jul 25 15:30:46 run sshd[10728]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=217.119.29.135 
Jul 25 15:30:48 run sshd[10728]: Failed password for invalid user public from 217.119.29.135 port 34292 ssh2
Jul 25 15:30:48 run sshd[10730]: Address 217.119.29.135 maps to gamma2-7.cust.smartspb.net, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
Jul 25 15:30:48 run sshd[10730]: Invalid user public from 217.119.29.135

Thousands of lines like this one

Jul 24 14:12:38 run sshd[2025]: error: connect_to 213.186.33.207 port 80: failed.
Jul 24 14:12:39 run sshd[2025]: error: connect_to 192.168.10.24 port 2110: failed.
Jul 24 14:12:39 run sshd[2025]: error: connect_to 195.130.65.50 port 80: failed.

OR

Jul 24 06:41:19 run sshd[9824]: error: connect_to 213.186.33.207 port 80: failed.
Jul 24 06:41:19 run sshd[13434]: Failed password for invalid user test from 202.28.123.191 port 37830 ssh2
Jul 24 06:41:20 run sshd[9824]: error: connect_to 213.186.33.207 port 80: failed.

And more like this

Jul 24 08:19:18 run sshd[20882]: pam_unix(sshd:auth): check pass; user unknown
Jul 24 08:19:18 run sshd[20882]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=puck748.server4you.de 
Jul 24 08:19:21 run sshd[20882]: Failed password for invalid user kk from 85.25.235.73 port 49213 ssh2
Jul 24 08:19:21 run sshd[20884]: Invalid user css from 85.25.235.73

It is simple, here is what you need to know

You can format it EXT4, but ext2 and ext3 are also OK ! ext2 and ext3 allow up to 16TB disks, and file sizes of up to 2TB, ext4 allows much more.

Any linux kernel newer than 2.6.31 should work just fine with “Advanced format” drives using the exact same steps in this article.

MBR only supports 2TB drives, you need GPT, so let us get started

1- apt-get update
2- apt get install parted
3- parted /dev/sdc
4- mklabel gpt
5- Answer yes to: Warning: The existing disk label on /dev/sdb will be destroyed and all data on this disk will be lost. Do you want to continue?
Yes/No? yes
6- mkpart primary ext4 0% 100% (to make a partition as big as the disk (will occupy starting from first megabyte (for alignment) to the end of disk))
7- quit

FYI, if you want multiple partitions, here are the 2 lines that should replace step 6
6- mkpart primary ext4 0% 40%
6- mkpart primary ext4 40% 100%

and remember to format both (sdc1 and sdc2) when you are done with parted

Now to formatting the drive

mkfs.ext4 /dev/sdc1

Before mounting it, i like ext4, but i don’t want a journaling OS on this drive that is not the system drive, so i will need do a few things to the drive first

Lazy writeback

tune2fs -o journal_data_writeback /dev/sdc1

No Journaling

tune2fs -O ^has_journal /dev/sdc1

Now to check what we have

dumpe2fs /dev/sdc1 |grep 'Filesystem features'

Or maybe if you want the whole thing on the screen

dumpe2fs /dev/sdc1 |more

if has_journal option exist when executing the first – you have journal on the file system

And there we are, Now we need to mount it at boot time by adding it to fstab, to do that, we will need the disk’s unique ID !

8- Now executing the following command will give you the unique ID of this new partition for use with fstab (The disk list we will edit below in step 10)
blkid /dev/sdc1
9- create the directory where you want to mount your hard disk, for example
mkdir /hds
mkdir /hds/3tb
10- Now, we add the following line to fstab, notice that noatime increases performance, but some applications might need or rely on it. postfix does not and i have verified that.

UUID=b7a491b1-a690-468f-882f-fbb4ac0a3b53       /hds/3tb            ext4     defaults,noatime                0       1

defaults and noatime are but only a couple of options, here are more options that you can add
nofail = If the disk is not present, continue booting
nobootwait = Limit the amount of time you plan to wait
noauto = Don’t mount it until I issue a “mount /dev/sdb1”, or mount “/hds/thisdisk” command

11- Now execute
mount -a

You are done,. if you execute
df -h
You should see your 2+TB hard drive in there !

To make sure the drive is aligned correctly, i like to write a file on it and see how fast that goes… so let us use a 2GB file

dd if=/dev/zero of=/hds/WD2000_3/deleteme.img bs=1M count=2000

Outcome came out (for a western digital black 2TB)
First run: 2097152000 bytes (2.1 GB) copied, 5.94739 s, 353 MB/s
Consecutive runs: 2097152000 bytes (2.1 GB) copied, 11.1405 s, 188 MB/s
Outcome came out for a western digital green 3TB
First run: 2097152000 bytes (2.1 GB) copied, 8.32337 s, 252 MB/s
Consecutive runs: 2097152000 bytes (2.1 GB) copied, 14.376 s, 146 MB/s

the consecutive runs give close results, what i printed here is the average

My old tablet (HP tc4200) had problems with the wireless adpater , A broadcom BCM4309

To find out what the Broadcom wireless adapter model is i issued

lspci -vvnn | grep 14e4

For yours, you may need to check with this website here as you may or may not need the sta or the b43legacy driver, in general here are the popular models

STA – BCM4311, BCM4312, BCM4313, BCM4321, BCM4322, BCM43224, BCM43225, **BCM43227, **BCM43228

b43 – BCM4306/3, BCM4311, BCM4312, BCM4318, BCM4320

b43legacy – BCM4301, BCM4306, BCM4306/2

http://www.linuxwireless.org/en/users/Drivers/b43#Supported_devices

The, now that i know… i edited /etc/apt/sources.list and added the contrib and non-free repositories

then

apt-get update

apt-get install firmware-b43-installer b43-fwcutter

And what do you know, just reboot and it works

This post is rather old, and everything is secure on the internet these days, so rather than FTP, it is recommended that you setup the new user with SFTP instead (Secure file transfer protocol), SCP is another option, but i have an sftp article ready for you here

So here is a quick guide to setting up a user to have access to a certain directory via FTP

You probably already use a Linux server, you access your files via SFTP or SCP, but you want to give someone access to a certain directory within.

Here is how it is done on a Debian squeeze machine

apt-get install pure-ftpd-common pure-ftpd

Then we need to add a group and default user for our program

groupadd ftpgroup
useradd -g ftpgroup -d /dev/null -s /etc ftpuser

pure-pw useradd test1 -u ftpuser -d /home/ftpusers/test1

pure-pw mkdb

This creates the file mentioned earlier called /etc/pureftpd.pdb, this file houses all information related to your virtual users

pure-pw passwd test1

Once password is set, update the database

pure-pw mkdb

To delete a user

pure-pw userdel test1

pure-pw show test1

pure-ftpwho

Create symlink to add PureDB to authentication methods

cd /etc/pure-ftpd/auth
ln -s ../conf/PureDB 50pure

Disable PAM authentication unless you need it

echo no > /etc/pure-ftpd/conf/PAMAuthentication

Disable UNIX authentication unless you need it

echo no > /etc/pure-ftpd/conf/UnixAuthentication

I accedientally pulled the power plug of a PC from the socket, and that PC was just starting to boot. The seagate hard drive inside stopped working, and the bad sectors turned out to affect the partition table, in any case, i slaved it on a windows vista PC, then into the Computer management, disk management panel, and what do you know, as if it has no paritions…

The solution to detect the boundaries of the 4 partitions it had is software called XXXX

Ran the software (The analyze option) , and what do you know, my partions exactly, 100MB made by Windows 7, a 479 GB partition for Windows, a 1GB swap partition for linux and an EXT3 partition for Linux…

So happily i asked the software to write the partitioning info to the disk, but the disk won’t hold the data, the bad sectors are where Windows writes the partition information

So, i ran down to the computer shop (In our building), and got the same exact drive (Seagate 500GB Model number xxx)

Mounted both on a Linux machine as slaves, both the damaged and the target.

To find out which one is SDC and which one is SDB, i watched as the linux machine booted, and as it booted, it threw in errors saying SDB all the time, so i know that SDB is the busted drive !

Installed gddrescue (apt-get install gddrescue), and ran it with the following command

ddrescue /dev/sdb /dev/sdc resumelog.log

(The additional log file helps us resume in case of interruption)

Once that is done, i put the new hard drive in a Windows machine, still can not see any partition info

1- Ran xxxx, it can see the 4 partitions, write changes… and what do you know, the partitions stick, we are good to go, i restart, but still, Windows can now see the partitions, but thinks drive G is not formated !

So i opened the command prompt (Elevated), then ran the command

chkdsk g: /f

the /f stands for fix, the thing took some time, but after the restart drive G works fine, all files are in there, and no one wants to kill me no more 🙂