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Earlier today I updated my Arch Linux system's kernel, using pacman, from 4.12.10 to 4.12.12. Before this update I was able to mount DVDs without a problem and watch them in VLC, but after this update I cannot. I cannot as they do not appear in my file manager's sidebar or in the "Discs" section of VLC's interface. I also noticed that my WiFi did not automatically connect for me as the systemd task of loading my WiFi profile failed on startup. This WiFi issue of mine was easy to fix I merely ran: sudo modprobe -a wl && sudo netctl restart <PROFILE> and everything was up and working again. Is such a simple solution possible with this DVD issue? To show you that this is not merely me not realizing that my DVD is able to be mounted I ran sudo fdisk -l and it returned:

Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 8AD72DC5-C104-4524-8C18-52759DC6C784

Device         Start        End    Sectors   Size Type
/dev/sda1       2048     264191     262144   128M EFI System
/dev/sda2     264192  946079743  945815552   451G Linux filesystem
/dev/sda3  946079744 1953525134 1007445391 480.4G Linux filesystem


Disk /dev/sdb: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: FF7E81B0-5B53-46B3-BA16-3763E91CB001

Device     Start        End    Sectors   Size Type
/dev/sdb1   2048 1953525134 1953523087 931.5G Linux filesystem

I see no mention of a DVD in there. dmesg | grep sr0 returns several lines along the lines of:

[  250.703204] sr 2:0:0:0: [sr0] unaligned transfer

where by 'along the lines of' I mean the same except the first part [ 250.703204]. lsblk returns:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931.5G  0 disk
├─sda1   8:1    0   128M  0 part /boot
├─sda2   8:2    0   451G  0 part /gentoo
└─sda3   8:3    0 480.4G  0 part /
sdb      8:16   0 931.5G  0 disk
└─sdb1   8:17   0 931.5G  0 part /data
sr0     11:0    1  1024M  0 rom

ls -l /dev/sr* /dev/cd* /dev/dvd* returns:

lrwxrwxrwx  1 root root        3 Sep 11 10:12 /dev/cdrom -> sr0
brw-rw----+ 1 root optical 11, 0 Sep 11 10:12 /dev/sr0

while pacman -Q linux && uname -r returns:

linux 4.12.12-1
4.12.12-1-ARCH

I just installed the linux-lts and linux-lts-headers packages and booted this alternate kernel to see whether this is due to the 4.12.12 kernel specifically and it's not. Booting with the 4.9.48 kernel also gives the same issue.

I have also tried running sudo modprobe -a cdrom with both kernels and it hasn't fixed this problem. I also tried reinstalling all native packages with:

for i in $(pacman -Qn | cut -d ' ' -f 1)
do
        sudo pacman -S "$i" --noconfirm
done

needless to say it failed to fix this problem.

  • how about ls -l /dev/sr* /dev/cd* /dev/dvd* ? – ivanivan Sep 11 '17 at 0:37
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    Please paste the output of pacman -Q linux && uname -r into your question. – jasonwryan Sep 11 '17 at 0:39
  • Added to question. – Brenton Horne Sep 11 '17 at 0:40
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    Not familiar with Arch Linux, but from the symptoms (wifi works after module reload, "unaligned transfer" errors), it looks like a mismatch between kernel modules, or between part of the kernel and the rest of the system. So the kernel update is probably incomplete, or you also need to update other parts of the system. BTW, DVDs are not partitioned, so fdisk doesn't work. They show up as /dev/sr*, and while the ISO filesystem can be mounted, usually need direct access with libdvdss to play the contents. – dirkt Sep 11 '17 at 5:57
  • @dirkt thanks for trying to help but I haven't the foggiest how to implement your idea. In order to complete the update I'd have to know what's stayed behind. The kernel update was with pacman so it should have been complete and automatic, as for other parts of my system that may need an update well I need someone to give me a clue as to what part as otherwise I haven't the foggiest. I have tried reinstalling all packages with libdvd in their name but it hasn't helped. – Brenton Horne Sep 11 '17 at 19:17

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