What do these errors mean?
Sep 30 23:52:29 ubuntu kernel: [ 1649.816032] [Hardware Error]: Machine check events logged
Sep 30 23:52:37 ubuntu kernel: [ 1657.885240] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:52:37 ubuntu kernel: [ 1657.887489] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:52:37 ubuntu kernel: [ 1657.887495] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:53:29 ubuntu kernel: [ 1709.597129] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:53:29 ubuntu kernel: [ 1709.599380] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:53:29 ubuntu kernel: [ 1709.599385] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:54:21 ubuntu kernel: [ 1761.309135] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:54:21 ubuntu kernel: [ 1761.311386] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:54:21 ubuntu kernel: [ 1761.311391] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:55:04 ubuntu AptDaemon: INFO: Quitting due to inactivity
Sep 30 23:55:04 ubuntu AptDaemon: INFO: Quitting was requested
Sep 30 23:55:04 ubuntu dbus[881]: [system] Activating service name='org.debian.apt' (using servicehelper)
Sep 30 23:55:05 ubuntu AptDaemon: INFO: Initializing daemon
Sep 30 23:55:05 ubuntu dbus[881]: [system] Successfully activated service 'org.debian.apt'
Sep 30 23:55:05 ubuntu AptDaemon.PackageKit: INFO: Initializing PackageKit compat layer
Sep 30 23:55:12 ubuntu kernel: [ 1813.021139] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:55:12 ubuntu kernel: [ 1813.023394] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:55:12 ubuntu kernel: [ 1813.023399] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:56:04 ubuntu kernel: [ 1864.737157] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:56:04 ubuntu kernel: [ 1864.739403] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:56:04 ubuntu kernel: [ 1864.739408] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:56:56 ubuntu kernel: [ 1916.453416] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:56:56 ubuntu kernel: [ 1916.455780] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:56:56 ubuntu kernel: [ 1916.455786] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:57:47 ubuntu kernel: [ 1968.157063] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:57:47 ubuntu kernel: [ 1968.159297] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:57:47 ubuntu kernel: [ 1968.159303] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:58:39 ubuntu kernel: [ 2019.869064] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:58:39 ubuntu kernel: [ 2019.871307] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:58:39 ubuntu kernel: [ 2019.871312] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:59:31 ubuntu kernel: [ 2071.581322] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Sep 30 23:59:31 ubuntu kernel: [ 2071.586202] sd 6:0:0:0: [sdb] Asking for cache data failed
Sep 30 23:59:31 ubuntu kernel: [ 2071.586208] sd 6:0:0:0: [sdb] Assuming drive cache: write through
Sep 30 23:59:41 ubuntu wpa_supplicant[1223]: WPA: Group rekeying completed with 00:24:b2:dd:cb:42 [GTK=CCMP]
Oct 1 00:00:05 ubuntu AptDaemon: INFO: Quitting due to inactivity
Oct 1 00:00:05 ubuntu AptDaemon: INFO: Quitting was requested
Oct 1 00:00:05 ubuntu dbus[881]: [system] Activating service name='org.debian.apt' (using servicehelper)
Oct 1 00:00:06 ubuntu AptDaemon: INFO: Initializing daemon
Oct 1 00:00:06 ubuntu dbus[881]: [system] Successfully activated service 'org.debian.apt'
Oct 1 00:00:06 ubuntu AptDaemon.PackageKit: INFO: Initializing PackageKit compat layer
Oct 1 00:00:23 ubuntu kernel: [ 2123.293360] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Oct 1 00:00:23 ubuntu kernel: [ 2123.295625] sd 6:0:0:0: [sdb] Asking for cache data failed
Oct 1 00:00:23 ubuntu kernel: [ 2123.295630] sd 6:0:0:0: [sdb] Assuming drive cache: write through
[Hardware Error]: Machine check events logged
. These machine errors aren't logged by default - please install themcelog
package and see the log file in/var/log/mcelog
. It should provide some details about the first line you're seeing. This is certainly hardware related.