What does this line of df output mean?

Ulysses_ · 12-07-2015, 12:08 PM

Trying to edit acronis rescue cd. It is easy to change any file in the initial ramdisk. But any changes have little to no effect because acronis launches their own proprietary binary for most tasks. However, that binary allows you to output system information, which includes something that looks like the output of df:

Code:

Filesystem                Size      Used Available Use Mounted on
/dev                    472.1M         0    472.1M   0% /dev
/dev/sr0                309.8M    309.8M         0 100% /mnt/cd_sxmkEc

What does the first line mean in normal df output?

EDIT: Show the formatting.

Ulysses_ · 12-07-2015, 12:16 PM

Note: the CD is booted in a VM with 1024 MB of ram, two hard drives of 4 GB and 50 GB with empty partitions, and a usb flash drive of 8 GB where 1.8 GB are occupied with data.

Ulysses_ · 12-07-2015, 12:42 PM

The system information output also includes these lines (in a file called summary.txt):

Code:

$ cat /proc/mounts
rootfs / rootfs rw 0 0
/proc /proc proc rw,relatime 0 0
/sys /sys sysfs rw,relatime 0 0
/dev /dev devtmpfs rw,relatime,size=483452k,nr_inodes=120863,mode=755 0 0
/dev/sr0 /mnt/cd_sxmkEc iso9660 ro,relatime,utf8 0 0

EDIT: Show the formatting.

lazydog · 12-07-2015, 12:43 PM

Not sure I am following what you are asking here but if you are asking what I think then all anyone can say is read the top line. It is self explanatory.

On a side note if you are going to post things that are formatted then you should enclose them in CODE tags so the foramt isn't lost, i.e.,

Code:

$ df
Filesystem              Type      Size  Used Avail Use% Mounted on
/dev/mapper/centos-root xfs        50G   12G   39G  23% /
devtmpfs                devtmpfs  7.7G     0  7.7G   0% /dev
tmpfs                   tmpfs     7.7G     0  7.7G   0% /dev/shm
tmpfs                   tmpfs     7.7G  817M  6.9G  11% /run
tmpfs                   tmpfs     7.7G     0  7.7G   0% /sys/fs/cgroup
/dev/mapper/centos-home xfs       408G  153M  408G   1% /home
/dev/sda1               xfs       497M  273M  225M  55% /boot
tmpfs                   tmpfs     7.7G  1.8M  7.7G   1% /opt/omd/sites/network/tmp

On the advance page paste your code then highlight it and click on the "#' to add the Code Tags.

Ulysses_ · 12-07-2015, 12:47 PM

What is self-explanatory? That a device called /dev is mounted on a directory called /dev? Where's the usb flash stick device then? And where is it mounted?

astrogeek · 12-07-2015, 01:48 PM

Quote:

Originally Posted by Ulysses_

...acronis launches their own proprietary binary for most tasks... that binary allows you to output system information, which includes something that looks like the output of df:

Code:

Filesystem                Size      Used Available Use Mounted on
/dev                    472.1M         0    472.1M   0% /dev
/dev/sr0                309.8M    309.8M         0 100% /mnt/cd_sxmkEc

What does the first line mean in normal df output?

Well, if it were normal df output it would appear to mean that a filesystem device /dev is mounted on directory /dev. In normal df output that would make no sense, at least to me. But you have already acknowledged that it is not normal df output, only something generated by Acronis' proprietary binary that looks like the output of df.

So the only useful answer I can see would have to be, ask Acronis what that means and why your other devices are not shown.

pan64 · 12-07-2015, 01:54 PM

remember, /dev is not a real device, but you can find all the available devices under /dev. So actually there is nothing to write as filesystem, because that is a virtual one (and also it is a "strange" one, because it has no driver ... ).

Emerson · 12-07-2015, 01:56 PM

I wouldn't call it virtual, it is pretty real tmpfs, filesystem that exixts in RAM.

Ulysses_ · 12-07-2015, 01:58 PM

I'd like to mount the usb drive and write to it, how is that done if /dev is already used as the mount directory of device /dev?

lazydog · 12-07-2015, 02:32 PM

Quote:

Originally Posted by Ulysses_

What is self-explanatory? That a device called /dev is mounted on a directory called /dev? Where's the usb flash stick device then? And where is it mounted?

Good question. Doesn't your Acronis mount usb automatically? What OS do you have installed on your system?

Emerson · 12-07-2015, 03:20 PM

Quote:

Originally Posted by Ulysses_

I'd like to mount the usb drive and write to it, how is that done if /dev is already used as the mount directory of device /dev?

Yes, and your root directory is mounted to /. Does it mean you cannot use your root directory and all its subdirectories?
Device filesystem is mounted to /dev, it contains all devices present in your system.

Ulysses_ · 12-07-2015, 04:18 PM

The Acronis Rescue live CD operating system is said by Acronis to be linux. It mounts usb drives and internal hard drives automatically and names them C:, D:, etc to avoid intimidating windows newbies. Somewhere in the files produced by the system information feature it shows the output of fdisk -l like this:

Code:

Disk /dev/sda: 4294 MB, 4294967296 bytes
255 heads, 56 sectors/track, 587 cylinders
Units = cylinders of 14280 * 512 = 7311360 bytes

   Device Boot      Start         End      Blocks  Id System
/dev/sda1               1         587     4191152   b Win95 FAT32

Disk /dev/sdb: 53.6 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks  Id System
/dev/sdb1               1        6528    52427776   7 HPFS/NTFS

Disk /dev/sdc: 8287 MB, 8287944704 bytes
158 heads, 46 sectors/track, 2227 cylinders
Units = cylinders of 7268 * 512 = 3721216 bytes

   Device Boot      Start         End      Blocks  Id System
/dev/sdc1               1        2228     8092672   b Win95 FAT32

So the usb stick seems to be /dev/sdc1 internally.

michaelk · 12-07-2015, 04:20 PM

What are you running i.e VirtualBox, VMware etc? Did you enable a USB port in the VM configuration and did you connect the flash drive to the VM? Does the drive show up in the output of the dmesg command?

I have not used Acronis but assume if the above conditions are meet then a device ID like /dev/sdc will automatically be created in /dev and that you can mount it anywhere in the directory tree like /mnt/flash.

I see that you have discovered the flash drive is recognized. So go ahead and manually mount it.

Ulysses_ · 12-07-2015, 04:23 PM

The backup feature can read from or write to the usb drive so it is definitely mounted, no issues with that.

But there is something funny about my tool for live CD editing. You can delete the entire directory tree and save the .iso, and if you then mount it or open it with isomaster, no files appear to be present. But it boots and works normally!

Isomaster by itself cannot be used for editing because the resulting .iso fails to boot, even if you do not modify anything. It says:

Starting Acronis Loader...
Boot failed, press any key...

Why might this be? What's an alternative tool that might work?

michaelk · 12-07-2015, 04:54 PM

What is the tool you are using and please explain the process for all who are unfamiliar...