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Tracking the slowdowns in the system, I was advised to check the files in the folder /var/log/lightdm/. There I see 4 files as on the image. What logs are recorded in each of them?

The other question is how to properly read file lightdm.log? It's content looks like this

[+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
[+0.00s] DEBUG: Starting Light Display Manager 1.8.4, UID=0 PID=1155
[+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/10-ubuntu.conf
[+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/50-greeter-wrapper.conf
[+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/50-guest-wrapper.conf
[+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
[+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/50-xserver-command.conf
[+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
[+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
[+0.00s] DEBUG: Registered seat module xlocal
...
[+4.52s] DEBUG: Session pid=1262: Logging to .xsession-errors
[+4.53s] DEBUG: Activating VT 7

Is this file being regenerated each time I log into the desktop? Or data is being appended to the file?

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1 Answer 1

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Read this Q&A if you want more info on the boot/login process.

lightdm.log is the log file where your display manager (also called login manager) lightdm write its messages.

After lightdm started the X-server, the X's first and last messages (like a header and a footer) will go into x-N.log, where N represents the display, just like in /var/log/Xorg.N.log which is the log file for the other messages from X.

The x-N-greeter.log file is the log file where the greeter (on ubuntu it is unity-greeter) messages are written, N again represents the display number.

You should start with lightdm.log and read it sequentially, and you will see that is is always reported when and where newer log files are created, e.g.:

[+0.22s] DEBUG: Logging to /var/log/lightdm/lightdm.log
...
[+0.31s] DEBUG: Logging to /var/log/lightdm/x-0.log
...
[+0.87s] DEBUG: Logging to /var/log/lightdm/x-0-greeter.log

Yes, those log files are regenerated on every reboot, but the previous log is saved with the .old suffix.

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    WOW! Thanks man for a detailed reply. Now, those time intervals (+0.22, +0.31,...) are they mean that action1 took 0.22s, action2 took 0.31s OR it means that action1 took 0.22s and action2 0.09s (0.31-0.22)? That part confused me on the first place. I am asking this because I saw some actions took like 27s so I am not sure if they lasted 27 seconds or I they lasted lastAction-previousAction.
    – ubuntico
    Dec 28, 2013 at 21:48
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    @ubuntico The time is the time elapsed since the process started when that line is printed. (So it is the second one, 0.31-0.22) If you can put your log on paste.ubuntu.com and put a link to it in your question, then we can look into it.
    – falconer
    Dec 28, 2013 at 21:52

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