Laptop sometimes not going to sleep

[DiBosco]

My laptop is sometimes not going to sleep. You can see it looks like it's about to then just as all the lights go out, they come back on again. It's like something is waking it, just after it sleeps.

Anyone come across this before?

Is there a way to send it to sleep from the command line to see what's going on? Similar instruction to shutdown -h now bit for sleep rather than shutdown.

Thanks.

[JoesCat]

Several years ago, people had problems with sleep due to linux updating some log files.

When it wakes-up, go to the command-line and try to see if there are any hints:
tail /var/logs/messages
or
tail /var/logs/syslog

[doktor5000]

@JoesCat: It's /var/log/ and tail by default shows only the last 10 lines, which in that case won't be really helpful.

@DiBosco: You should try the pm- commands, either pm-suspend, pm-suspend-hybrid or pm-hibernate.
All of them also have additional options for special video quirks, maybe that helps.

For reference, how do you send it to sleep normally?