How to format Flash/Pen Drive in Linux

Note: I have used my device name and number in examples, you have to change it
as your device name and number, otherwise  unwanted device data will be wiped
out.
 Put your USB flash drive in one of your computer's free USB ports. After a few
seconds, Linux will automatically recognize it and an icon for it will appear on
your desktop. If pen drive doesn't mounted automatically, login as root and try
to mount it, still it is not mounted there may be a problem with pen drive or it
is defective.

Finding device: 
 Very very first thing is you should to know what device you are working with.
For that you can use any one of the following methods.

Method 1:  Using  ls /dev/sd*  command
First make sure your usb drive is not plugged in. Then run:

[venu@ras ~]$ ls /dev/sd*
/dev/sda   /dev/sda10  /dev/sda12  /dev/sda2  /dev/sda6  /dev/sda8
/dev/sda1  /dev/sda11  /dev/sda13  /dev/sda5  /dev/sda7  /dev/sda9
Once you have done that, put in your pen drive and run the above command again.

[venu@ras ~]$ ls /dev/sd*
/dev/sda   /dev/sda10  /dev/sda12  /dev/sda2  /dev/sda6  /dev/sda8  /dev/sdb
/dev/sda1  /dev/sda11  /dev/sda13  /dev/sda5  /dev/sda7  /dev/sda9  /dev/sdb1
 
Whatever drive (ex sdb) was not there before is your pen drive. From the above
list my pen drive is sdb. Don't be confuse with /dev/sdb and /dev/sdb1,  sdb is
a drive and sdb1 is first partition in that drive.

Method 2:  Using df command
[venu@ras ~]$ df
Filesystem           1K-blocks      Used Available Use% Mounted on

/dev/sda10            29753556   8008860  20208884  29% /
/dev/sda12            19840892   1528664  17288088   9% /msfiles
/dev/sda11            21825108  16772836   3925716  82% /venu
tmpfs                  1032232         0   1032232   0% /dev/shm
/dev/sdb1              1947636         4   1947632   1% /media/VENU
 
As you can see above my pen drive (/dev/sdb1) is mounted at /media/VENU. If you
have any doubt about which one is your pen drive, do same thing as in method1.
Run df command before and after inserting  pen drive.

Method 3:   dmesg | tail
[venu@ras ~]$ dmesg | tail
sdb: assuming drive cache: write through
SCSI device sdb: 3903359 512-byte hdwr sectors (1999 MB)
sdb: Write Protect is off
sdb: Mode Sense: 0b 00 00 08
sdb: assuming drive cache: write through
 sdb: sdb1
sd 8:0:0:0: Attached scsi removable disk sdb
sd 8:0:0:0: Attached scsi generic sg1 type 0
usb-storage: device scan complete
SELinux: initialized (dev sdb1, type vfat), uses genfs_contexts
Method 4:   mount -l
[venu@ras ~]$ mount -l
/dev/sda10 on / type ext3 (rw) [/]
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda12 on /msfiles type ext3 (rw) [/msfiles1]
/dev/sda11 on /venu type ext3 (rw) [/venu1]
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
/dev/sdb1 on /media/VENU type vfat (rw,nosuid,nodev,shortname=winnt,uid=500)
[VENU]
Method 5:   fdisk -l 
fdisk command need root privileges. So login as root and run the command:

[root@ras ~]# fdisk -l
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System

/dev/sda1   *           1        5099    40957686    7  HPFS/NTFS
/dev/sda2            5100       60800   447418282+   f  W95 Ext'd (LBA)
/dev/sda5            5100       10198    40957686    7  HPFS/NTFS
/dev/sda10          50994       54817    30716248+  83  Linux
/dev/sda11          54818       57622    22531131   83  Linux
/dev/sda12          57623       60172    20482843+  83  Linux
/dev/sda13          60173       60694     4192933+  82  Linux swap / Solaris

Disk /dev/sdb: 1998 MB, 1998519808 bytes
32 heads, 63 sectors/track, 1936 cylinders
Units = cylinders of 2016 * 512 = 1032192 bytes

   Device Boot      Start         End      Blocks   Id  System

/dev/sdb1               1        1936     1951456+   b  W95 FAT32
fdisk -l displays all detected drives even drive is unmounted.

Formatting pen drive:
 First decide which file system you want. FAT32 is probably the file system you
want, but that's up to you. Ext3 may not be work on windows, It asks for fomatt-
ing.

1.Once you have Identified your pen drive, unmount it.
[root@ras ~]# umount /dev/sdb1
2.Format pen drive now.
 Depending on distribution different commands are available for formatting, but
in general most used ones that I have seen are mkdosfs or mkfs.vfat for FAT32
and  mke2fs or mkfs.ext3 for Linux filesystems.

For Ms-Dos or Windows file system:
 Use mkdosfs -n "Label" -I /dev/sdx, Replace Label with the name you want the
pen drive to have and /dev/sdx with your drive.

[root@ras ~]# mkdosfs -n "KVMREDDY" -I /dev/sdb1
mkdosfs 2.11 (12 Mar 2005)
                              or
[root@ras ~]# mkfs.vfat -n "KVMREDDY" -I /dev/sdb1
mkfs.vfat 2.11 (12 Mar 2005)
           (Note: I – capital letter of i )

 If you don't want any Label then no need to supply option n. switch I will
force mkdosfs to work properly but it  is not mandatory, you can remove that
also.

For Linux File system:
 Use mkfs.ext3 -L "Label"  /dev/sdx for ext3 file system or mke2fs -L 'Label'
/dev/sdx for ex2, Replace Label with the name you want the pen drive to have
and /dev/sdx with your drive.

Ext3 file system:

[root@ras ~]# mkfs.ext3 -L "KVMREDDY" /dev/sdb1
mke2fs 1.39 (29-May-2006)
Filesystem label=KVMREDDY
OS type: Linux
.............................
[root@ras ~]# 
ext2 file system:  

[root@ras ~]# mke2fs -L 'VENU' /dev/sdb1
mke2fs 1.39 (29-May-2006)
Filesystem label=VENU
OS type: Linux
...........................
[root@ras ~]# 
 After formatting you will be returned to the prompt then remove and insert the
pen drive to have mounted again.