Command line to mount USB flash drives in Linux

The subject is not new and nothing beats the device notifier icon in KDE asking you what to do with a newly inserted flash drive. This post however, is meant to serve only as a note to me, regarding the safest procedure of setting up and mounting a flash drive from the command line.

The current state of affairs is like this: We have a 32GB flash drive that is to be plugged in to a remote LAMP server where we want to place daily database backups. We only have access to the server via ssh so in order to automate the procedure, we are going to initially format the drive using the ext4 file system and then label it so that we won't care about the actual SCSI port that he device will use in the future.

Initial formatting and labelling

After the device has been plugged in for the first time, the easiest way to determine the actual SCSI port is to find the lines containing the word SCSI in the kernel displayed messages. This is as easy as :

[root@skymnos ~]# dmesg | grep SCSI
SCSI subsystem initialized
Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
scsi0 : SCSI emulation for USB Mass Storage devices
sd 1:0:0:0: [sdb] Attached SCSI disk
sd 0:0:0:0: [sda] Attached SCSI removable disk
[root@skymnos ~]# 

Alternatively we could use the udisks --monitor command before pluggin in the device. This would produce output like the following:

[root@skymnos-wifi ~]# udisks --monitor
Monitoring activity from the disks daemon. Press Ctrl+C to cancel.
added:     /org/freedesktop/UDisks/devices/sde
added:     /org/freedesktop/UDisks/devices/sde1

So now we know that out flush drive is located under /dev/sda and the partition that we are going to work with is /dev/sda1. To format it we will use the mkfs.ext4 command with the -L option to specify a label for our file-system.

[root@skymnos ~]# mkfs.ext4 -L dbBackups /dev/sda1 
mke2fs 1.41.12 (17-May-2010)
Filesystem label=dbBackups
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
1949696 inodes, 7790336 blocks
389516 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
238 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
        4096000

Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 39 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@skymnos ~]# 

Mounting

The -L dbBackups switch that we previously used in order to format the drive, tells mkfs to create a file system with a label of dbBackups. Now if you plug this to a system running a decent window manager with udev, this would be automatically mounted under /media/dbBackups. We are going the mimic the same behaviour.

[root@skymnos ~]# mkdir /media/dbBackups/
[root@skymnos ~]# mount -L dbBackups /media/dbBackups/
[root@skymnos ~]# df -h /media/dbBackups
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              30G  172M   28G   1% /media/dbBackups
[root@skymnos ~]# 

A few more details: Since this is going to be backup storage disk, our lives will become much easier if we create a directory with full read-write permissions inside the drive like this:

[root@skymnos ~]# mkdir /media/dbBackups/data
[root@skymnos ~]# chmod o+w /media/dbBackups/data/
[root@skymnos ~]# 

So to sum it up. Mounting the flash drive on the remote server from my office machine requires -- well, apart from having someone plug the drive into a USB port doing something like this:

[thanassis@skymnos ~]$ sudo mount -L dbBackups /media/dbBackups/
[thanassis@skymnos-wifi ~]$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              68G  5.1G   62G   8% /
tmpfs                1006M   88K 1006M   1% /dev/shm
/dev/sdb1              30G  172M   28G   1% /media/dbBackups
[thanassis@skymnos ~]$ 

And what if I wanted the system to attempt to mount the drive each time it boots? In that case all I would have to do is add a line like /bin/mount -L dbBackups /media/dbBackups/ in the /etc/rc.d/rc.local file