Toggle readonly filesystem for changes - linux

I have a readonly filesystem on my bootable usb drive.
I want to modify some text files in there and then bring it back to readonly after modify it.
I tried :
sudo hdparm -r0 /dev/sdb
I also tried :
mount -o remount,rw /dev/sdb
mount: /dev/sdb: mount point not mounted or bad option.
mount -o remount,rw /dev/sdb1
cannot remount /dev/sdb1 read-write, is write-protected.
But it's stays readonly.
I do not want to make any other changes to the partition it's important to keep all the rest of the partition/mbr as is.
Any idea?

Related

Programmatically obtaining USB file system format

I need to mount a USB drive to an embedded system, running Linux. The USB could be in FAT, NTFS or ExFAT format.
How can i handle this in code so that I pass proper type in mount command such as
mount -t vfat /dev/sda1 /mnt
So I have tried mount with:
mount -t vfat,ntfs /dev/sda1 /mnt
This command gives invalid argument, but it successfully mounts the USB if USB is in NTFS or VFAT format. However if i try to give
mount -t vfat,ntfs,exfat /dev/sda1 /mnt
The command fails.
Any pointers will be really helpful.
From the mount manual page:
If no -t option is given, or if the auto type is specified,
mount will try to guess the desired type. Mount uses the blkid
library for guessing the filesystem type...
Is libblkid available for your embedded system?
Try:
mount -t auto /dev/sda1 /mnt
or
mount /dev/sda1 /mnt
And as mentioned in the comments, make sure the kernel on your embedded system supports exfat.

mount already mounted or busy

I have an Amazon EC2 instance (Ubuntu 12.04) to which I have attached two 250 GB volumes. Inadvertently, the volumes got unmounted. When I tried mounting them again, with the following command,
sudo mount /dev/xvdg /data
this is the error I get :
mount: /dev/xvdg already mounted or /data busy
Then, I tried un-mounting it as follows :
umount /dev/xvdg but it tells me that the volume is not mounted.
umount: /dev/xvdg is not mounted (according to mtab)
I tried lsof to check for any locks but there weren't any.
The lsblk output is as below :
Any help will be appreciated. What do I need to do to mount the volumes back without losing the data on them?
Ok, figured it out. Thanks #Petesh and #mootmoot for pushing me in the right direction. I was trying to mount single volumes instead of a RAID 0 array. The /dev/md127 device was running so I stopped it first with the following command :
sudo mdadm --stop /dev/md127
Then I assembled the RAID 0 array :
sudo mdadm --assemble --uuid <RAID array UUID here> /dev/md0
Once the /dev/md0 array became active, I mounted it on /data.
Try umount /dev/xvdg* and umount /data and then
mount /dev/xvdg1 /data

UBIFS mount in busybox via fstab does not recognize relatime option

I am getting this error when I try to mount my UBIFS filesytem:
mount -o remount,rw /config
UBIFS error (pid 1265): ubifs_parse_options: unrecognized mount option "relatime" or
missing value
The content of my fstab is :
root#drgos:~# cat /etc/fstab
# WARNING: this is an auto generated file, please use uci to set static filesystems
/dev/ubi0_0 /config ubifs ro 0 0
And when I type mount the result is :
root#drgos:~# mount
rootfs on / type rootfs (rw)
none on /proc type proc (rw,relatime)
none on /sys type sysfs (rw,relatime)
tmpfs on /dev type tmpfs (rw,relatime,size=512k)
none on /dev/pts type devpts (rw,relatime,mode=600)
/dev/ubi0_0 on /config type ubifs (ro,relatime)
none on /proc/bus/usb type usbfs (rw,relatime)
I do not understand why I have the option relatime since that one is not present in my fstab!
I am using BusyBox v1.11.2 (2014-01-13 09:35:41 CET) multi-call binary.
These options are dependent on the Linux kernel version. relatime is a general mount options. relatime is the default for newer Linux kernels. Other filesystems may quietly ignore unknown options, whereas ubifs is failing. You can try mount -o remount,rw,noatime,norelatime /config. Your mount command shows the /config directory is mounted with relatime; this is information that busybox mount applet collected.
This information is collected with the getmntent_r() function. If busybox is dynamically linked, then the 'C' library may be giving this information as part of the *mnt_opts* string.
The idea with mount -o remount,rw,noatime,norelatime /config is to try and over-ride this information so that UbiFs will be happy with its mount options. The other way is to simply umount and then mount again manually.
umount /config
mount -t ubifs /dev/ubi0_0 /config
This way previous mount information will not be retrieved.

How to determine the type of file system on an SD Card

How to determine the type of file system on an SD Card (this card is not yet mounted. I need to determine the file system type so that i can mount the SDCard through a program according to the file system type)
Or from the terminal. For example "mount -t ext3 /dev/sdc1 /mnt"
You might do a file -s /dev/sdc1 and it could recognize the filesystem data.
And you might do mount -t auto /dev/sdc1 /mnt to have mount recognize it.

mount point /dev/sdb1/mnt is not a directory

I'm partway through an installation of Arch Linux and, following the online instructions, I'm mounting /dev/sdb1/mnt.
When I input
mount /dev/sdb1/mnt
it returns
mount: you must specify the filesystem type
Using both auto and ext4 (my filesystem type, I'm fairly certain)
mount auto /dev/sdb1/mnt
I get
mount: mount point /dev/sdb1/mnt is not a directory
What is going on here?
You are missing a space:
# right here---v
mount /dev/sdb1 /mnt
The mount command wants a device and a directory. /dev/sdb1 is the device, and /mnt is the directory.

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