I'm running Ubuntu MATE 20.04 on one of my machines, and noticed that for some reason, it appears to be using two different greeters. It looks like LightDM for the login screen, but something else for the lock screen. How can I change it to be consistent? (And preferably use LightDM on the lock screen so that the power options are available)?

Login:

Lock:

I'm attempting to record a 1080 @ 30FPS video from a Logitech C920 webcam. Simple, right? Well, apparently not.

First, I tried on my desktop running 16.04 using Ubuntu's built-in Cheese application. The preview streams perfectly fine at 30FPS, but as soon as I start recording, the frame rate drops drastically to probably around ~15FPS (I don't know exactly since Cheese doesn't provide an FPS meter).

Next, I tried again on my desktop running 16.04 using guvcview. Unfortunately, the version in the default repos for 16.04, 2.02, has a bug which causes it to record video as a single still frame. Arghh... so then I installed 2.05 from an unofficial PPA. This solved the aforementioned bug, however, when I go to record video (using H.264 from the camera's hardware encoder) the first second or so of the video records perfectly, but then the frame rate drops to between 3 and 5 FPS.

Finally, to make sure it wasn't just a problem with my desktop, I installed guvcview version 2.05 on my laptop running 18.04, but once again, when I go to record video (using H.264 from the camera's hardware encoder) the first second or so of the video records perfectly, but then the frame rate drops to between 3 and 5 FPS.

So what the heck is going on here? Is this an issue with libuvc compatibility with the Logitech C920? I know it's not an issue of under-powered hardware, as I have a 6-core AMD CPU in my desktop and a quad-core 3rd gen i7 in my laptop.

I just installed Lubuntu 18.04.1 on an old desktop with an AMD Althon 64 x2 4800+ CPU, and while overall it's running fine, my kernel logs are getting flooded with CPU frequency errors from powernow_k8:

I did some Googling and found many old posts about how to fix this, but none of the commands worked (not surprising since I'm sure a lot has changed since 2008)...

Anybody have a suggestion on how I can fix this? Honestly I don't even care about dynamic frequency scaling working, I just want powernow_k8 to quit flooding my kernel log....

When I run intel_gpu_top on my 16.04 system, it crashes at line 145 in intel_mmio.c:

~$ intel_gpu_top
(intel_gpu_top:25862) intel-mmio-CRITICAL: Test assertion failure function intel_mmio_use_pci_bar, file ../../lib/intel_mmio.c:145:
(intel_gpu_top:25862) intel-mmio-CRITICAL: Failed assertion: !(error != 0)
(intel_gpu_top:25862) intel-mmio-CRITICAL: Last errno: 13, Permission denied
(intel_gpu_top:25862) intel-mmio-CRITICAL: Couldn't map MMIO region
Stack trace:
  #0 [_init+0x83d9]
  #1 [_init+0x6036]
  #2 [_init+0x1301]
  #3 [__libc_start_main+0xf0]
  #4 [_init+0x2f61]
  #5 [<unknown>+0x2f61]
Test (null) failed.
**** DEBUG ****
(intel_gpu_top:25862) intel-mmio-CRITICAL: Test assertion failure function intel_mmio_use_pci_bar, file ../../lib/intel_mmio.c:145:
(intel_gpu_top:25862) intel-mmio-CRITICAL: Failed assertion: !(error != 0)
(intel_gpu_top:25862) intel-mmio-CRITICAL: Last errno: 13, Permission denied
(intel_gpu_top:25862) intel-mmio-CRITICAL: Couldn't map MMIO region

This guy has the same problem.

Is this a bug? How can I fix this?

I use both IntelliJ IDEA and Android Studio for development, and for the longest time I've been trying to figure out why the two programs, from the same company, and built on the same codebase, and using the exact same font settings (and same text anti-aliasing method) will render the text in the editor pane differently.

For example, with both programs set to use DejaVu Sans Mono, 12pt:

• Android Studio:

  

• IntelliJ IDEA:

  

You can clearly see the difference, the font is thinner and/or almost like it isn't anti-aliased in IntelliJ.

This has been driving me up the wall, as I find the text in IntelliJ much harder on the eyes.

Has anybody else experienced this before and know how to fix it?

So, I love having an external HDD with Ubuntu on it and bring able to boot it on any computer and be right at home in Linux with all my files and programs.

Now here's my question: if I install the Nvidia drivers, will it only boot properly on a system with an Nvidia GPU, or will it still work just fine on systems with an Intel or AMD GPU?

Normally I would just try it and see what happens, but I would prefer not to screw up my drive and have to spend a few hours fixing it. (I've already nuked one Ubuntu install beyond repair when messing with the Nvidia drivers about a year ago)

So from what I've read online, if AHCI is enabled in the BIOS, I should be able to hot-swap a SATA drive and it will supposedly "just work".

However, that has not been my experience.

When I hot-swap a SATA drive on my system, it is never detected. It doesn't show up in lsblk, it doesn't show up in Gparted, nothing even shows in dmesg.

So, I am wondering what the issue is?

I am using 16.04 on an Asus M5A97 R2.0

Edit to address Takkat's suggestion:

I have no such option:

Update 9

I decided to try an experiment. I removed the SSD from my desktop, and temporarily put it into my Dell Latitude laptop. Lo and behold, it loaded the initrd on an order of magnitude faster, shaving 6 seconds off the boot time...

I'm a little confused now... maybe GRUB has an issue with my motherboard's chipset?

Update 8

So I noticed something interesting about the HDD activity light. When loading the initrd, it's almost as if the light is being PWMed at a 10% duty cycle or something. This makes me wonder if GRUB's read is not optimized, maybe something like it's doing an OS call to read each byte rather than reading the image as a byte stream?

Update 7

It appears that loading the initial ramdisk is a large part of the issue.

Inside GRUB, I pressed C for the manual command prompt. I then proceeded to type every single line from my default configuration in one at a time (inputting those UUIDs was painful!), and noted the time the command took at complete. Here's what I found:

• Most of the commands completed instantaneously
• The command to load the kernel took about one second
• The command to load the initial ramdisk took 7 seconds

After typing in all the lines from the config file, I then proceed to run boot. From the time I hit enter to the time the login screen appeared, it took about 7.5 seconds.

Of interest is the fact that the initrd image it's loading is 36MB. So if it took 7 seconds to load, then it's only reading it at 5MB/sec!

The disk activity light on my tower stays on for the entire 7 seconds...

Also here's an interesting snippet from the Wikipedia page about initrd:

Other Linux distributions (such as Fedora and Ubuntu) generate a more generic initrd image. These start only with the device name of the root file system (or its UUID) and must discover everything else at boot time. In this case, the software must perform a complex cascade of tasks to get the root file system mounted

Update 6

Nathan Osman requested the boot time in single-user mode in chat.

From the time I hit F10 in GRUB to the time the prompt appears, it takes 13 seconds.

Also, I was talking to Zanna and Rinzwind in chat and they both have an 8-second startup from the time the hit the power button. My 20 seconds is from GRUB. If I counted POST time, it would be even longer!

Update 5

Ubuntu can read my SSD at its maximum speed of 550MB/sec...

Update 4

So I removed the quiet splash $vt_handoff parameters from the boot command in GRUB on my laptop (keep in mind this laptop does not have an SSD), and noticed a very interesting thing during the boot sequence:

It hangs on this line for 15 seconds:

[    4.374390] init: plymouth-upstart-bridge respawnng too fast, stopped

Here's a (low quality) picture:

Not sure what the significance of that is...

Update 3

I timed the bootup of one of my other machines running 14.04 (keep in mind this machine doesn't have an SSD), and from the time I hit enter in GRUB till the login screen shows up, it takes 40 seconds.

After hitting enter, it sits at that same blank purple screen for 20 seconds, after which the Ubuntu animation loads and it takes another 20 seconds before landing at the login screen.

I looked at the output from dmesg, but I can't quite tell where it finished booting. I think it finished at 25 seconds. Here's the last few lines:

[   24.916824] wlan0: associated
[   24.916852] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[   25.215550] init: kdm main process (869) killed by TERM signal
[   25.441216] vboxdrv: module verification failed: signature and/or  required key missing - tainting kernel
[   25.445587] vboxdrv: Found 2 processor cores.
[   25.446142] vboxdrv: fAsync=0 offMin=0x18c offMax=0x960
[   25.446228] vboxdrv: TSC mode is 'synchronous', kernel timer mode is 'normal'.
[   25.446230] vboxdrv: Successfully loaded version 4.3.36_Ubuntu (interface 0x001a000b).
[   25.476940] vboxpci: IOMMU not found (not registered)
[   33.174926] init: plymouth-upstart-bridge main process ended, respawning
[   36.495811] init: anacron main process (933) killed by TERM signal

If I interpreted it correctly, it seems to be a universal GRUB issue.

Update 2

I was able to confirm that it is a GRUB issue by setting the background color of GRUB to green by using the command line accessed by pressing C when in GRUB.

When I hit enter, I get a blank green screen for ~15 seconds before the Ubuntu boot animation loads...

Update

I think the issue is that GRUB is taking a long time to load the kernel image.

Question

I have installed Ubuntu 16.04 on my Samsung 850 Pro 512GB SSD, and I can't understand why my boot time is 20 seconds. (From the time I hit enter in GRUB). Keep in mind that the 20 I am referencing is 17 to the login screen, and then another 3 to the desktop)

Also, not sure if this is relevant or not, but:

• Ubuntu is installed in MBR mode, because I despise UEFI.
• I have the proprietary Nvidia drivers installed

Looking at the image generated by systemd-analyze plot > bootimage2, my startup apparently took 3 seconds?

And looking at dmesg, my startup apparently took 4 seconds. But I timed it with my stopwatch and it took 20 seconds! (Not including POST time) Again, keep in mind that the 20 I am referencing is 17 to the login screen, and then another 3 to the desktop)

Here's how the startup sequence goes:

• POST
• GRUB loads
• I start my stopwatch as I hit ENTER
• I get a blank purple screen for ~15 seconds
• I see the Ubuntu boot animation for two seconds
• I land on the login screen
• I stop the stopwatch
• I enter my password, hit enter, and start my stopwatch again.
• After 3 seconds I land on the desktop
• I stop my stopwatch again.

Here's the complete output from dmesg: http://paste.ubuntu.com/23955108/

And here are the first lines from the output of systemd-analyze blame:

   365ms dev-sda5.device
   327ms networking.service
   287ms accounts-daemon.service
   286ms ModemManager.service
   233ms systemd-logind.service
   216ms apport.service
   213ms grub-common.service
   209ms ondemand.service
   200ms irqbalance.service
   183ms speech-dispatcher.service
   178ms apparmor.service
   160ms gpu-manager.service
   148ms thermald.service
   148ms pppd-dns.service
   146ms systemd-user-sessions.service
   142ms alsa-restore.service
   140ms console-setup.service
   137ms rsyslog.service
   105ms NetworkManager.service
   104ms upower.service
   102ms avahi-daemon.service
   100ms systemd-udev-trigger.service

These people have the same problem:

• https://ubuntuforums.org/showthread.php?t=2325045
• https://www.bleepingcomputer.com/forums/t/598260/booting-ubuntu-temporarily-stuck-on-a-purple-screen/
• And it seems even people with ARCH have this problem...

Any ideas?

I use headphones with my computer, and when I reboot, the volume gets set to 100%.

Hence, when the logon screen comes up, the drum sound plays through my headphones at maximum volume, which is... well I think you know where I'm going with this...

So, how can I make the volume stay the same across reboots?

I am using Ubuntu 14.04

As is common knowledge, SSDs have a limited number of PE (Program-Erase) cycles before the NAND cells die.

Therefore, it is very helpful to know how much data has been written to your SSD, in order to determine how much longer it will last before the NAND dies.

I have a Samsung 850 Pro 512GB SSD, and I am running Ubuntu 14.04.

How can I get the TBW (Total-Bytes-Written) for my drive?

I just got a brand new Samsung 850 Pro SSD, and I would like to install Ubuntu 14.04 onto it.

I have read some pretty ugly stories of data loss with the 850 series SSDs when using Linux due to bugs in the kernel, as well as bugs in the TRIM operation.

I have done my research, but most of what I'm finding is very outdated. For example, see this question, and this Reddit thread, as well as this one.

My question is, what is the current status? Have all major the bugs been worked out yet?

I have both Ubuntu 14.04 and Xubuntu 16.04 installed on one of my older desktops.

While both work fine, I experience screen tearing while dragging windows around in Xubuntu. However, I do not experience it on Ubuntu.

It is using the motherboard's built-in AMD graphics chip.

Note: This exact situation also holds true for my main desktop with a GTX650 graphics card...

At this point, I'm thinking it has something to do with Untiy being a 3D DE, and XFCE being a 2D DE...

I have Ubuntu installed on an external HDD, and I use it as a portable install that I can take with me wherever I go.

Today I booted it on a friend's iMac, and after Software Updater asked me to install updates. So I did.

Since at that point I was done with it, I shut off the computer and unplugged the external HDD. Immediately after which I started the iMac again so it would boot back into OSX.

To my utter shock, horror, and confusion, I was met with a GRUB rescue screen!

How is that possible? Ubuntu is installed on the external HDD, not the internal one! How the heck did GRUB end up on the iMac's internal HDD?

More importantly, how do I fix this?

After I used dd to make a USB drive from an Ubuntu ISO, I am unable to format it for normal use.

I ran:

sudo dd if="ubuntu-16.04-desktop-amd64.iso" of="/dev/sdb" bs=4M

In order to create a bootable USB drive.

However, after I was done with it, I wanted to format it as FAT32 and use it like a normal USB drive.

No problem, should be easy, right? WRONG.

I have tried:

• Using the included Disks application to format it. It threw an error about corrupt GPT tables and wouldn't give me an override option.
• Using Gparted the erase the current partition table and write a new MBR table [completed successfully]
• After that I created a FAT32 partition spanning the entire volume, and remounted. [Showed up in Files, good so far]
• Attempted to copy a file to it. It thre an error saying the medium was read-only.
• Erased the partition table again in Gparted and this time created an NTFS partition spanning the entire disk. [Same RO error when attempting to copy a file onto it]
• Repeated the procedure trying this time with EXT4 [Same RO error]
• Repeated procedure trying a GTP table instead of an MBR table. {Same error]

Finally, I tried running:

sudo hdparm -r0 /dev/sdb

And remounted. Still the same error. Keep in mind that I remounted it after formatting it each time.

I am at a total loss. Has dd bricked my USB drive?

If I run:

sudo apt-get dist-upgrade

It upgrades all the packages on my system, including LibreOffice, Chrome & Firefox, which for me is undesirable.

How can I tell Ubuntu to only install system patches, whilst allowing me to manually upgrade my applications?

I am using Ubuntu 14.04 x64

What I have done

I have set up a LAMP webserver using these commands:

sudo apt-get install apache2
sudo apt-get install mysql-server
sudo apt-get install php5 libapache2-mod-php5
sudo /etc/init.d/apache2 restart

Then I installed phpmyadmin with:

sudo apt-get install phpmyadmin

The problem

The problem is that when I go to http://localhost/phpmyadmin/, I get this:

phpMyAdmin - Error
The json extension is missing. Please check your PHP configuration.

What I've tried

I've tried:

• https://superuser.com/questions/639945/how-to-fix-the-phpmyadmin-error-json-extension-is-missing
• https://stackoverflow.com/questions/27818040/phpmyadmin-error-the-json-extension-is-missing
• https://www.youtube.com/watch?v=WoLKOBmikXo

System info

• Clean install of Ubuntu 14.04 x64

I was reading on this page that running

ubuntu-support-status

Will "...print the exact status of your system."

However, if I run that command, it crashes and throws an exception. Here's the stacktrace:

dev@dev-Ubuntu:~$ ubuntu-support-status
Traceback (most recent call last):
  File "/usr/bin/ubuntu-support-status", line 133, in <module>
    pkg.name, support_tag)
  File "/usr/bin/ubuntu-support-status", line 49, in get_maintenance_status
    raise Exception("No date tag found")
Exception: No date tag found

And I got this GUI popup:

I found this, this and this on Launchpad....

I am using 14.04 x64

This is an odd question and I don't think I would even have a use for it, but;

Can I bring up tty1 on one monitor and tty2 on the other, both at the same time?

In my machine I have two Nvidia graphics cards. I am running Ubuntu 14.0.4.2 x64.

My primary card is a GTX650, and my secondary card is an 8600GT.

I would like to have dual monitors, with one monitor per card. (Yes, I know the GTX650 has 3 outputs, but I need the S-Video on the 8600GT)

By dual monitors I mean the statndard setup where you can drag a window from one to the other.

When I hook up the second monitor to the 8600GT, nothing happens. So I went into the Nvidia Control Panel and enabled it. After restarting, I can move my cursor to the second screen, but the cursor is a white "X". Some googling revealed this means that there is an X server running on it. But I don't understand why it can't behave just like I had plugged another monitor into my GTX650.

By the way, this works fine with the open-source drivers.

Similar to this: Can't get Dual Monitors to work on different GPUs

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