16.04 (Xenial Xerus) Known bugs and work-a-rounds

[ericnotar]

This thread is for just what it says: known bugs and work-arounds.

This forum is populated by users such as yourself. For bugs to be brought to the attention of Ubuntu developers (who don't hang out here) they must be reported. The Ubuntu Forums do not act as a bug report mechanism.

So here is one bug that is affecting many Lenovo users RTL8723AU NO WIFI or eratic, I am sure someone is working on it.
I already try all possible solution posted in the forum and sometimes it works sometimes not.
I hope the solution is found very soon.
Thank you very much

[nukedathlonman]

I have an HP Pavilion notebook. I've filed one bug report on the AMDgpu package - it randomly kicks the video out on "Carrizo" based APU's. Put the computer to sleep then resume will cause the display to work again for a short bit of time. If one has it enabled, you can also ssh into the affected machine and operate it remotely from another computer. There's no errors when the fault occurs, it's just a random black screen.

There's a problem with the Realtek RTL8723BE on numerous makes and models of notebooks with antenna selection, and this affects all Linux distro's. There is an update that has a fix in GIT hub. It was easy to compile the driver from git up and add the module to the kernel in 15.10, but due to secure boot and kernel singing it's difficult to work around in 16.04. The changes are coming in a future kernel release (may even be in the newer kernels by now).

I'm throwing in the towel this weekend and restoring my 15.10 backup copy. I can get by with the Realtek driver bug, but until AMDgpu is more stable with Carrizo, I have to stick to the older closed AMD Crimson display driver.

[ericnotar]

First tried restarting network manager by running sudo service network-manager restart. It worked but was not a permanent resolution.

Try this by MBWD in AskUbuntu: create this script at /etc/systemd/system/wifi-resume.service (the one the OP posted only worked for the active session; on reboot it had to be called again):

#/etc/systemd/system/wifi-resume.service
#sudo systemctl enable wifi-resume.service
[Unit]
Description=Restart networkmanager at resume
After=suspend.target
After=hibernate.target
After=hybrid-sleep.target

[Service]
Type=oneshot
ExecStart=/bin/systemctl restart network-manager.service

[Install]
WantedBy=suspend.target
WantedBy=hibernate.target
WantedBy=hybrid-sleep.target

Then just issue this command in terminal to activate it: sudo systemctl enable wifi-resume.service.

This solution, and works both after suspend and after reboot.
However, even after that was fixed, I get the same behavior that used to happen on wake from suspend when I try to switch wifi networks: the wifi is essentially dead, with the two arrows, and the applet says "device not ready." I can restart the wifi by issuing sudo service network-manager restart, but I can't switch networks.

[Cavsfan]

Edit: This is no longer necessary with the release of Xenial Xerus 16.04. See the red below.

If you find that autoremove wants to only keep the latest kernel. Or even if you boot into a previous kernel autoremove will remove the most current kernel,
here is a workaround until Bug #1440608 is fixed.

There are 2 important parts to this workaround.
This is not my work but Jarnos's work and it works well allowing 2 kernels to be kept as you would expect it to do.

You could make a backup copy first if you want: sudo cp /etc/kernel/postinst.d/apt-auto-removal /etc/kernel/postinst.d/apt-auto-removal.bak
1) Edit and replace /etc/kernel/postinst.d/apt-auto-removal with this: (from post #40 on that bug)

#!/bin/sh -e 
# Author: Steve Langasek <steve.langasek@canonical.com>
#         Jarno Suni <8@iki.fi>
#
# Mark as not-for-autoremoval those kernel packages that are:
#  - the currently booted version
#  - the kernel version we've been called for, if not removing it
#  - the latest kernel version (determined using rules copied from the
#    grub package for deciding which kernel to boot)
#  - the second-latest kernel version, if the booted kernel version is
#    already the latest to ensure a fallback remains available in the
#    event the newly-installed kernel at this ABI fails to boot. In the
#    common case, this results in exactly two kernels saved, but it can
#    result in three kernels being saved.  It's better to err on the
#    side of saving too many kernels than saving too few.
#
# We generate this list and save it to /etc/apt/apt.conf.d instead of marking
# packages in the database because this runs from a postinst script, and apt
# will overwrite the db when it exits.


eval $(apt-config shell APT_CONF_D Dir::Etc::parts/d)
test -n "${APT_CONF_D}" || APT_CONF_D="/etc/apt/apt.conf.d"
config_file=${APT_CONF_D}/01autoremove-kernels

eval $(apt-config shell DPKG Dir::bin::dpkg/f)
test -n "$DPKG" || DPKG="/usr/bin/dpkg"
# No specific apt config variable for dpkg-query?
DPKG_QUERY="${DPKG}-query"

triggered_version="$1"
if [ -n "$1" ]
then
    regex_argument="$(echo "$1" | sed -e 's#\.#\\.#g')"
    #Check if the kernel given in argument is desired to be removed:
        ${DPKG_QUERY} -W -f='${Package} ${db:Status-Abbrev}\n' |
         grep -Eq '^((linux|kfreebsd|gnumach)-image|linux-image-extra)-'"$regex_argument"' (r|p)H' &&
          triggered_version=""
fi

running_version="$(uname -r)"

version_test_gt ()
{
    local version_test_gt_sedexp="s/[._-]\(pre\|rc\|test\|git\|old\|trunk\)/~\1/g"
    local version_a="`echo "$1" | sed -e "$version_test_gt_sedexp"`"
    local version_b="`echo "$2" | sed -e "$version_test_gt_sedexp"`"
    $DPKG --compare-versions "$version_a" gt "$version_b"
    return "$?"
}
list="$(${DPKG_QUERY} -W -f='${db:Status-Abbrev} ${Package}\n' |
 awk '/^ii  (linux|kfreebsd|gnumach)-image-[0-9]+\./ && $2 !~ /-dbg$/ { print $2 }' |
 xargs apt-mark showauto |
 sed -e 's#\(linux\|kfreebsd\|gnumach\)-image-##')"

latest_version=""
previous_version=""
for i in $list; do
    if version_test_gt "$i" "$latest_version"; then
        previous_version="$latest_version"
        latest_version="$i"
    elif version_test_gt "$i" "$previous_version"; then
        previous_version="$i"
    fi
done

if [ "$latest_version" != "$running_version" ]
then
    # We have at least two kernels that we have reason to think the
    # user wants, so don't save the second-newest version.
    previous_version=""
fi

kernels="$(echo "$latest_version
$triggered_version
$running_version
$previous_version" | sort -Vu | sed -e 's#\.#\\.#g' )"

generateconfig() {
    cat <<EOF
// DO NOT EDIT! File autogenerated by $0
APT::NeverAutoRemove
{
EOF
    apt-config dump --no-empty --format '%v%n' 'APT::VersionedKernelPackages' | while read package; do
        for kernel in $kernels; do
            echo "   \"^${package}-${kernel}$\";"
        done
    done
    echo '};'
}
generateconfig > "${config_file}.dpkg-new"
mv "${config_file}.dpkg-new" "$config_file"

2) Create a cron job that will run at startup to perform an autoremove like this: (this is from post #26 and #27 of that bug and also created by Jarnos)
Create this file: /etc/cron.d/boot-auto-removal that contains the following:

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

@reboot   root    /etc/kernel/postinst.d/apt-auto-removal

That's it. Upon a reboot, you will be able to keep at least 2 kernels.

You may also want to add your name to that bug as this has affected every version of Ubuntu back to 12.04.

Edit: the more people on that bug, the more attention it gets.

Also here is the original thread about this: http://ubuntuforums.org/showthread.php?t=2251168

Edit: If you changed your /etc/kernel/postinst.d/apt-auto-removal file with the above, you could either leave it or replace it with what came out with Xenial Xerus' release:

#!/bin/sh
set -e
# Mark as not-for-autoremoval those kernel packages that are:
#  - the currently booted version
#  - the kernel version we've been called for
#  - the latest kernel version (as determined by debian version number)
#  - the second-latest kernel version
#
# In the common case this results in two kernels saved (booted into the
# second-latest kernel, we install the latest kernel in an upgrade), but
# can save up to four. Kernel refers here to a distinct release, which can
# potentially be installed in multiple flavours counting as one kernel.

eval $(apt-config shell APT_CONF_D Dir::Etc::parts/d)
test -n "${APT_CONF_D}" || APT_CONF_D="/etc/apt/apt.conf.d"
config_file="${APT_CONF_D}/01autoremove-kernels"

eval $(apt-config shell DPKG Dir::bin::dpkg/f)
test -n "$DPKG" || DPKG="/usr/bin/dpkg"

list="$("${DPKG}" -l | awk '/^[ih][^nc][ ]+(linux|kfreebsd|gnumach)-image-[0-9]+\./ && $2 !~ /-dbg(:.*)?$/ && $2 !~ /-dbgsym(:.*)?$/ { print $2,$3; }' \
   | sed -e 's#^\(linux\|kfreebsd\|gnumach\)-image-##' -e 's#:[^:]\+ # #')"
debverlist="$(echo "$list" | cut -d' ' -f 2 | sort --unique --reverse --version-sort)"

if [ -n "$1" ]; then
    installed_version="$(echo "$list" | awk "\$1 == \"$1\" { print \$2;exit; }")"
fi
unamer="$(uname -r)"
if [ -n "$unamer" ]; then
    running_version="$(echo "$list" | awk "\$1 == \"$unamer\" { print \$2;exit; }")"
fi
latest_version="$(echo "$debverlist" | sed -n 1p)"
previous_version="$(echo "$debverlist" | sed -n 2p)"

debkernels="$(echo "$latest_version
$installed_version
$running_version
$previous_version" | sort -u | sed -e '/^$/ d')"
kernels="$( (echo "$1
$unamer"; for deb in $debkernels; do echo "$list" | awk "\$2 == \"$deb\" { print \$1; }"; done; ) \
   | sed -e 's#\.#\\.#g' -e '/^$/ d' | sort -u)"

generateconfig() {
    cat <<EOF
// DO NOT EDIT! File autogenerated by $0
APT::NeverAutoRemove
{
EOF
    for package in $(apt-config dump --no-empty --format '%v%n' 'APT::VersionedKernelPackages'); do
        for kernel in $kernels; do
            echo "   \"^${package}-${kernel}$\";"
        done
    done
    echo '};'
    if [ "${APT_AUTO_REMOVAL_KERNELS_DEBUG:-true}" = 'true' ]; then
        cat <<EOF
/* Debug information:
# dpkg list:
$(dpkg -l | grep '\(linux\|kfreebsd\|gnumach\)-image-')
# list of installed kernel packages:
$list
# list of different kernel versions:
$debverlist
# Installing kernel: $installed_version ($1)
# Running kernel: $running_version ($unamer)
# Last kernel: $latest_version
# Previous kernel: $previous_version
# Kernel versions list to keep:
$debkernels
# Kernel packages (version part) to protect:
$kernels
*/
EOF
    fi
}
generateconfig "$@" > "${config_file}.dpkg-new"
mv -f "${config_file}.dpkg-new" "$config_file"
chmod 444 "$config_file"

And if you changed that file and have changed it back, you should delete the file /etc/cron.d/boot-auto-removal as well.

[howefield]

Toshiba Laptop : appstreamcli maxing out CPU and not able to use apt.

Workaround :

sudo kill appstreamclipid
cd ~/Downloads
wget https://launchpad.net/ubuntu/+archive/primary/+files/appstream_0.9.4-1ubuntu1_amd64.deb 
wget https://launchpad.net/ubuntu/+archive/primary/+files/libappstream3_0.9.4-1ubuntu1_amd64.deb 
sudo apt install libappstream3*.deb 
sudo apt install appstream*.deb

[banceu_sergiu_ione]

Toshiba L50D-C-18x AMD 8700P R6 ( windows 10 / ubuntu 16.04 *2 days old install )

Wi-Fi connection droping

product: RTL8821AE 802.11ac PCIe Wireless Network Adapter
driver: rtl881ae

I had manage to change the module driver parameters and set */int_clear=N and the connection does not drop anymore ( ~12hrs passed since ).

Anyway the driver looks to not function properly but it keep the connection up

• turn off/on the wireless from keyboard ( FN+F12 *in my case ) make the wifi only to switch on Airplane mode on/off and it not really switch off the hardware.
• after the switch on from keyboard the device it connects back but the wifi icon is shown as the connection is wired and the wifi network it not shown in menu anymore

Terminal:

 grep [[:alnum:]] /sys/module/rtl8821ae/parameters/*

output:

/sys/module/rtl8821ae/parameters/debug:0
/sys/module/rtl8821ae/parameters/disable_watchdog:N
/sys/module/rtl8821ae/parameters/fwlps:Y
/sys/module/rtl8821ae/parameters/int_clear:Y
/sys/module/rtl8821ae/parameters/ips:Y
/sys/module/rtl8821ae/parameters/msi:Y
/sys/module/rtl8821ae/parameters/swenc:N
/sys/module/rtl8821ae/parameters/swlps:N

run:

 echo "options rtl8821ae int_clear=N" | sudo tee /etc/modprobe.d/rtl8821ae.conf

REBOOT

check if the parameter had been changed after restart = yes.


This is what I got so far. At least the network connection don't drop anymore and for now I will avoid the wifi switch off/on.

[Cavsfan]

If anyone did the kernel autoremoval change I mentioned above, it is not necessary now with the release of Xenial.
I wanted to test it with a fresh release and today the 3rd kernel came though and it lets you keep 2 kernels now.

See above if you made the changes I posted.

regards

[damianfanaro]

Hi,
In my case, the work around was to unload and load again the 'rtl8xxxu' module after every reboot.
Here is the command:

sudo rmmod rtl8xxxu && sudo modprobe rtl8xxxu

I'm running Linux Mint 18 (Sarah) - Kernel 4.4.0-21-generic.
Laptop: Lenovo Yoga 13

On previous Kernel versions I had to install the driver (rtl8723au) manually.

I hope this issue to be fixed on future Kernel releases.

[timgood]

Many Ubuntu and derivative users with Logitech webcams are having problems with 'chipmunk' voices on Skype. This is caused by a kernel regression bug and has been reported. A temporary fix is to add "usbcore.autosuspend=-1" to /etc/default/grub on the line commencing GRUB_CMDLINE_LINUX_DEFAULT. This line now looks like this in my version (yours may differ):

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash usbcore.autosuspend=-1 nomodeset video=uvesafb:mode_option=1920x1080-24,mtrr=3,scroll=ywrap"

After you have made and saved the changes, open a terminal and

sudo update-grub

. After a reboot Skype will work normally. USB devices will not suspend, so will stay 'awake' on full power, which is why this is only an interim fix. Hope this helps.

[ltrtiger2]

I do that as well. I also use this:

alias Clean='sudo apt-get autoremove && sudo apt-get autoclean'

Gets rid of the un-needed stuff.

Nice tip/shortcut. Thank you both!