Check and modify connection mtu

To check:

[root@lxd-node3 ~]# netstat -i
Kernel Interface table
Iface             MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
ens10            1450      455      0      0 0           671      0      0      0 BMRU
eth0             1500       28      0      0 0            32      0      0      0 BMRU
lo              65536        0      0      0 0             0      0      0      0 LRU

Modify temporarily:

ifconfig eth0 mtu 1450

Permanently: edit /etc/sysconfig/network-scripts/ifcfg-eth0 file and add:

MTU=1450

lxd: Fix version in snap

 snap refresh lxd --channel=3.18

fedora: Lockdown a kernel version

Fedora typically keeps 3 latest kernel versions. However, what if you want to keep an old specific kernel version which is known to work well with your system? First, we need to install a dnf plugin that allows us to keep a specific version of any package:

sudo dnf install python3-dnf-plugins-extras-versionlock

Lets find all available kernel versions for your system:

sudo dnf list kernel --showduplicates

Install that specific version of the kernel:

sudo dnf install kernel-5.3.7-301.fc31

And lock it:

sudo dnf versionlock add kernel-5.3.7-301.fc31

To remove the lock:

sudo dnf versionlock delete kernel-5.3.7-301.fc31

Dell Precision 5540 - Battery drains in sleep mode

Run the following command to check the suspend mode:

cat /sys/power/mem_sleep 

If the output looks like this:

[s2idle] deep

It means that very inefficient suspend mode is active (drains battery from 100% to 0 in 9 hours). To enable "deep" mode, edit file /etc/default/grub and append "mem_sleep_default=deep" to GRUB_CMDLINE_LINUX:

GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="rd.lvm.lv=fedora/root rd.lvm.lv=fedora/swap rhgb quiet mem_sleep_default=deep"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=true

Apply changes:

sudo grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg

Restart your laptop and verify changes:

$ cat /sys/power/mem_sleep 
s2idle [deep]