Know your Raspberry Pi


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We shall use simple Linux commands to know more about the Raspberry Pi.

Exploring /proc¶

The /proc file system is the place to look for all sorts of information. For example:

# cat /proc/cpuinfo
Processor       : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS        : 697.95
Features        : swp half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xb76
CPU revision    : 7Hardware        : BCM2708
Revision        : 0003
Serial          : 00000000f90cbb6b

The output tells us that we are on a system with an ARM processor with a BogoMIPS of 697.95. Among the CPU features..

You can obtain the information about the memory usage from the file /proc/meminfo:

# cat /proc/meminfo
MemTotal:         234968 kB
MemFree:           56840 kB
Buffers:           10380 kB
Cached:           126004 kB
..
..

Various other information about your system can be obtained such as:

# cat /proc/sys/kernel/hostname
raspberry
# cat /proc/sys/kernel/ostype
Linux
# cat /proc/sys/kernel/osrelease
3.2.27
# cat /proc/sys/kernel/pid_max
32768
# cat /proc/sys/kernel/poweroff_cmd
/sbin/poweroff

USB Devices

To explore the USB devices connected to your Pi, we can use the lsusb command

# lsusb -t/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=hub, Driver=hub/3p, 480M
        |__ Port 1: Dev 3, If 0, Class=vend., Driver=smsc95xx, 480M

The above output corresponds to no USB devices connected to the Pi. If you connect any other device(s), the command’s output will change accordingly. For example, when I plugged in two external storage disks, here is the what the output corresponds to

# lsusb -t
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=hub, Driver=hub/3p, 480M
        |__ Port 1: Dev 3, If 0, Class=vend., Driver=smsc95xx, 480M
        |__ Port 2: Dev 6, If 0, Class=stor., Driver=usb-storage, 480M
        |__ Port 3: Dev 5, If 0, Class=stor., Driver=usb-storage, 480M

Mount points and mounting disks

The df and mount commands can be used to obtain information about the secondary storage disks attached to your Raspberry Pi:

# df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs          3.7G  2.1G  1.4G  61% /
/dev/root       3.7G  2.1G  1.4G  61% /
devtmpfs        115M     0  115M   0% /dev
tmpfs           115M     0  115M   0% /dev/shm
tmpfs           115M  1.1M  114M   1% /run
tmpfs           115M     0  115M   0% /sys/fs/cgroup
tmpfs           115M     0  115M   0% /media
/dev/mmcblk0p1   51M   16M   36M  31% /boot# mount
/dev/root on / type ext4 (rw,noatime,user_xattr,barrier=1,data=ordered)
devtmpfs on /dev type devtmpfs (rw,relatime,size=117396k,nr_inodes=29349,mode=755)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
..
..

The mount command is also used to mount external disks. Insert your external USB disk and note the output of dmesg

# dmesg[79827.845946] usb 1-1.3: new high-speed USB device number 5 using dwc_otg
[79827.947579] usb 1-1.3: New USB device found, idVendor=1058, idProduct=1111
[79827.947611] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[79827.947628] usb 1-1.3: Product: My Book 1111
[79827.947641] usb 1-1.3: Manufacturer: Western Digital
[79827.947655] usb 1-1.3: SerialNumber: 574341563535323139373832
[79827.954851] scsi0 : usb-storage 1-1.3:1.0
[79828.953242] scsi 0:0:0:0: Direct-Access     WD       My Book 1111     1032 PQ: 0 ANSI: 4
[79828.954734] scsi 0:0:0:1: CD-ROM            WD       Virtual CD 1111  1032 PQ: 0 ANSI: 4
[79828.956757] scsi 0:0:0:2: Enclosure         WD       SES Device       1032 PQ: 0 ANSI: 4
[79828.966489] sd 0:0:0:0: [sda] 1952151552 512-byte logical blocks: (999 GB/930 GiB)
[79828.968510] sd 0:0:0:0: [sda] Write Protect is off
[79828.968547] sd 0:0:0:0: [sda] Mode Sense: 23 00 10 00
...
[79829.068725]  sda: sda1
[79829.075284] sd 0:0:0:0: [sda] No Caching mode page present
[79829.095857] sd 0:0:0:0: [sda] Assuming drive cache: write through
[79829.102133] sd 0:0:0:0: [sda] Attached SCSI disk

The device that you inserted corresponds to the device file /dev/sda. Now let us see what partitions are there on this device

# fdisk -l /dev/sdaDisk /dev/sda: 999.5 GB, 999501594624 bytes
255 heads, 63 sectors/track, 121515 cylinders, total 1952151552 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0002ae3fDevice Boot      Start         End      Blocks   Id  System
/dev/sda1        2048    952151551   976074752    7 HPFS/NTFS/exFAT

As you can see, there is only one partition on this disk. If you again run the mount command, you will see that this partition hasn’t yet been mounted. The mount command can be used for this purpose

# mount -t ntfs  /dev/sda1 /var/disk1/

If you now rerun the mount command, you will see this line in the output

/dev/sda1 on /var/disk1 type fuseblk (rw,relatime,user_id=0,group_id=0,allow_other,blksize=4096)

Now, you can read/write from this disk by going to /var/disk1. One drawback of this mechanism is that you will have to do this manually everytime you restart the Pi. Assuming that you will have the disk always connected to your Pi, you can add the following entry to your /etc/fstab file

/dev/sda1       /var/disk1                      ntfs    defaults                          0 0
/dev/sdb1       /var/disk2                      ntfs    defaults                          0 0

I have another disk connected to the Pi and hence I add both entries to the file. Save the file and you will see that when you reboot your Pi, these disks will be ready to use.

Now you are ready to devise a file sharing/backup solution using one of the various possible mechanisms.