Foreword
Because Raspberry Pi 4b is a special case, and so far there is no official offer can be mounted directly on the Raspberry Pi system image 4b, and 4b for previously released versions of the new model does not provide good support.
So update plug-ins or update the system may occur the following problems:
Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C.UTF-8; apt-get update 2>&1' with exit code '100':
This article provides a solution to this issue.
Specific issues
Specific error code, you can compare it with your code:
Server.java
Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C.UTF-8; apt-get update 2>&1' with exit code '100': Get:1 file:/var/cache/openmediavault/archives InRelease Ign:1 file:/var/cache/openmediavault/archives InRelease Get:2 file:/var/cache/openmediavault/archives Release Ign:2 file:/var/cache/openmediavault/archives Release Get:3 file:/var/cache/openmediavault/archives Packages Ign:3 file:/var/cache/openmediavault/archives Packages Get:4 file:/var/cache/openmediavault/archives Translation-en Ign:4 file:/var/cache/openmediavault/archives Translation-en Get:3 file:/var/cache/openmediavault/archives Packages Ign:3 file:/var/cache/openmediavault/archives Packages Get:4 file:/var/cache/openmediavault/archives Translation-en Ign:4 file:/var/cache/openmediavault/archives Translation-en Get:3 file:/var/cache/openmediavault/archives Packages Ign:3 file:/var/cache/openmediavault/archives Packages Get:4 file:/var/cache/openmediavault/archives Translation-en Ign:4 file:/var/cache/openmediavault/archives Translation-en Get:3 file:/var/cache/openmediavault/archives Packages Ign:3 file:/var/cache/openmediavault/archives Packages Get:4 file:/var/cache/openmediavault/archives Translation-en Ign:4 file:/var/cache/openmediavault/archives Translation-en Get:3 file:/var/cache/openmediavault/archives Packages Ign:3 file:/var/cache/openmediavault/archives Packages Get:4 file:/var/cache/openmediavault/archives Translation-en Ign:4 file:/var/cache/openmediavault/archives Translation-en Get:3 file:/var/cache/openmediavault/archives Packages Ign:3 file:/var/cache/openmediavault/archives Packages Get:4 file:/var/cache/openmediavault/archives Translation-en Ign:4 file:/var/cache/openmediavault/archives Translation-en Get:3 file:/var/cache/openmediavault/archives Packages [1069 B] Get:4 file:/var/cache/openmediavault/archives Translation-en Ign:4 file:/var/cache/openmediavault/archives Translation-en Get:5 http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian buster InRelease [15.0 kB] Hit:6 http://mirrors.tuna.tsinghua.edu.cn/raspberrypi buster InRelease Get:7 http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian buster/main Sources [11.4 MB] Err:7 http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian buster/main Sources File has unexpected size (11350904 != 11350828). Mirror sync in progress? [IP: 183.222.102.76 80] Hashes of expected file: - Filesize:11350828 [weak] - SHA256:2080fdd5bfa43842d350f338f920c1bc537aa7f40a9095504772a7241ba52753 - SHA1:b6a1b284c7512b8ad0eea2618b2058bfcae1cb8b [weak] - MD5Sum:32b82c8547daaff00d223c8cb462acea [weak] Release file created at: Fri, 27 Mar 2020 22:51:18 +0000 Ign:9 https://dl.bintray.com/openmediavault-plugin-developers/usul buster InRelease Hit:10 https://download.docker.com/linux/debian buster InRelease Get:11 https://dl.bintray.com/openmediavault-plugin-developers/usul buster Release [4363 B] Hit:13 http://packages.openmediavault.org/public usul InRelease Fetched 4363 B in 13s (327 B/s) Reading package lists... E: Failed to fetch http://183.222.102.76/cache/mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/dists/buster/main/source/Sources.xz?ich_args2=392-28124503039578_574e8b1e35a7d749e734ef3666544963_10001002_9c896c29d4c4f1d6953a518939a83798_4a770034bf2db31bc5e0861b958e4fa3 File has unexpected size (11350904 != 11350828). Mirror sync in progress? [IP: 183.222.102.76 80] Hashes of expected file: - Filesize:11350828 [weak] - SHA256:2080fdd5bfa43842d350f338f920c1bc537aa7f40a9095504772a7241ba52753 - SHA1:b6a1b284c7512b8ad0eea2618b2058bfcae1cb8b [weak] - MD5Sum:32b82c8547daaff00d223c8cb462acea [weak] Release file created at: Fri, 27 Mar 2020 22:51:18 +0000 E: Failed to fetch http://183.222.102.65/cache/mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/dists/buster/main/binary-armhf/Packages.xz?ich_args2=392-28124513039608_af3257cb9619ae1550a259fa412a8924_10001002_9c896c29d4c4f1d6953a518939a83798_60c5e3374eaa05658ba5bf091e3e49ad E: Some index files failed to download. They have been ignored, or old ones used instead.
Solution
The method now is to find a kernel update.
sudo apt-get install --reinstall raspberrypi-bootloader raspberrypi-kernel
After updating the kernel, you can update the plug-in or update the system . However, this method is not once and for all, the next may still have the same problem, it is necessary to update the kernel again.