Battery Replacement
The battery in C720 #1, which is over six years old, would no longer hold a charge. I purchased a Dentsing AP13J3K replacement battery from Amazon. I opened the C720, removed the old battery, inserted the new one, closed up the case, and all was well. It was an impressively easy fix.Sleeping & Waking
Sometime around last October Linux Mint 19 switched from kernels in the 5.0 series to kernels in the 5.4 series. Mint 20 uses 5.4 series kernels. The 5.0 kernels on the C720 went to sleep properly when the lid closed, and woke properly when the lid opened. The 5.4 kernels appeared to go to sleep correctly, but when the lid opened did a cold boot. Because this problem happens immediately on wake, and because sleep appears to work correctly, there is no useful information in the logs; this appears to be a very hard problem to diagnose.Here is my work-around to use the 5.0.0-32 kernel (the last I installed via updates) on a vanilla Linux Mint installation:
- Install Linux Mint 20.1 MATE edition.
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Add repositories using Administration/Software Sources:
- deb http://archive.ubuntu.com/ubuntu bionic main restricted universe multiverse
- deb http://archive.ubuntu.com/ubuntu bionic-updates main restricted universe multiverse
- deb http://security.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse
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Install kernel 5.0.0-32-generic:
sudo apt-get install linux-headers-5.0.0-32 linux-headers-5.0.0-32-generic linux-image-5.0.0-32-generic linux-modules-5.0.0-32-generic linux-modules-extra-5.0.0-32-generic
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Edit /etc/default/grub to show the menu of kernels:
GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=15 -
Edit /etc/default/grub so that your most recent choice of kernel becomes the default:
GRUB_SAVEDEFAULT=true
GRUB_DEFAULT=saved - Run update-grub
Disk & Home Directory Encryption
Note that you should ideally install Linux Mint 20.1 with full-disk encryption. The release notes explain:The move to systemd caused a regression in ecrypts which is responsible for mounting/unmounting encrypted home directories when you login and logout. Because of this issue, please be aware that in Mint 20 and newer releases, your encrypted home directory is no longer unmounted on logout: https://bugs.launchpad.net/ubuntu/+source/gnome-session/+bug/1734541.Mint 19 with a full-disk encryption had this problem but I haven't been able to reproduce it with Mint 20 and the 5.0.0-32 kernel. Home directory encryption works, but will leave its contents decrypted after you log out, rather spoiling the point.
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