Since being upgraded from jessie to stretch, several of my machines have started emitting the following messages while processing cron.daily:
(in /var/log/syslog) Aug 31 06:30:48 HOSTNAME systemd[1]: Requested transaction contradicts existing jobs: Transaction is destructive. (in /var/log/auth.log) Aug 31 06:30:48 HOSTNAME su[32025]: pam_systemd(su:session): Failed to create session: Input/output error Aug 31 06:30:48 HOSTNAME systemd-logind[1301]: Failed to start session scope session-11179.scope: Transaction is destructive. org.freedesktop.systemd1.TransactionIsDestructive The mention of freedesktop in one of the messages suggests that this may be somehow X/GUI related, but all machines which are doing this are headless servers with no X server installed, so they shouldn't be touching anything obviously related to freedektop.org. Googling "org.freedesktop.systemd1.TransactionIsDestructive" just gets me a handful of people having system startup/shutdown problems, which would seem to support the "it's GUI desktop related" assumption, but doesn't really provide any explanation of what's actually going wrong (if anything - systemd is rather chatty even when everything is just fine). Looking at the larger context in auth.log, this comes in the middle of starting up and shutting down several su sessions from root to nobody, all of which succeed aside from the one which generates these errors. So, in practical terms, what do these messages actually mean, beyond just "a su session failed to start"? Is it anything to be concerned about? -- Dave Sherohman