j'ai trouvé les logs de X ,
dans ~/.local/share/xorg/Xorg.0.log
386.877] (--) Log file renamed from "/home/alain/.local/share/xorg/Xorg.pid-22030.log" to "/home/alain/.local/share/xorg/Xorg.0.log"
[ 386.877]
X.Org X Server 1.20.10
X Protocol Version 11, Revision 0
[ 386.877] Build Operating System: Linux 4.19.0-13-amd64 x86_64 Debian
[ 386.877] Current Operating System: Linux sid 5.10.0-2-amd64 #1 SMP Debian 5.10.9-1 (2021-01-20) x86_64
[ 386.877] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.10.0-2-amd64 root=UUID=356787df-36be-449a-8129-e219dbf2cab8 ro quiet
[ 386.877] Build Date: 06 January 2021 09:33:33AM
[ 386.877] xorg-server 2:1.20.10-2 (https://www.debian.org/support)
[ 386.877] Current version of pixman: 0.40.0
[ 386.877] Before reporting problems, check http://wiki.x.org
to make sure that you have the latest version.
[ 386.877] Markers: (--) probed, (**) from config file, (==) default setting,
(++) from command line, (!!) notice, (II) informational,
(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[ 386.877] (==) Log file: "/home/alain/.local/share/xorg/Xorg.0.log", Time: Tue Feb 2 11:35:08 2021
[ 386.877] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
[ 386.877] (==) No Layout section. Using the first Screen section.
[ 386.877] (==) No screen section available. Using defaults.
[ 386.877] (**) |-->Screen "Default Screen Section" (0)
[ 386.877] (**) | |-->Monitor "<default monitor>"
[ 386.877] (==) No monitor specified for screen "Default Screen Section".
Using a default monitor configuration.
[ 386.877] (==) Automatically adding devices
[ 386.877] (==) Automatically enabling devices
[ 386.877] (==) Automatically adding GPU devices
[ 386.877] (==) Max clients allowed: 256, resource mask: 0x1fffff
[ 386.877] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
[ 386.877] Entry deleted from font path.
[ 386.878] (==) FontPath set to:
/usr/share/fonts/X11/misc,
/usr/share/fonts/X11/100dpi/:unscaled,
/usr/share/fonts/X11/75dpi/:unscaled,
/usr/share/fonts/X11/Type1,
/usr/share/fonts/X11/100dpi,
/usr/share/fonts/X11/75dpi,
built-ins
[ 386.878] (==) ModulePath set to "/usr/lib/xorg/modules"
var/log/Xorg.0.log
[ 2.933] (--) Log file renamed from "/var/log/Xorg.pid-2002.log" to "/var/log/Xorg.0.log"
[ 2.934]
X.Org X Server 1.20.10
X Protocol Version 11, Revision 0
[ 2.934] Build Operating System: Linux 4.19.0-13-amd64 x86_64 Debian
[ 2.934] Current Operating System: Linux sid 5.10.0-1-amd64 #1 SMP Debian 5.10.5-1 (2021-01-09) x86_64
[ 2.934] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.10.0-1-amd64 root=UUID=356787df-36be-449a-8129-e219dbf2cab8 ro nomodeset=1 quiet
[ 2.934] Build Date: 06 January 2021 09:33:33AM
[ 2.934] xorg-server 2:1.20.10-2 (https://www.debian.org/support)
[ 2.934] Current version of pixman: 0.40.0
[ 2.934] Before reporting problems, check http://wiki.x.org
to make sure that you have the latest version.
[ 2.934] Markers: (--) probed, (**) from config file, (==) default setting,
(++) from command line, (!!) notice, (II) informational,
(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[ 2.934] (==) Log file: "/var/log/Xorg.0.log", Time: Sun Jan 24 13:58:21 2021
[ 2.936] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
[ 2.938] (==) No Layout section. Using the first Screen section.
[ 2.938] (==) No screen section available. Using defaults.
[ 2.938] (**) |-->Screen "Default Screen Section" (0)
[ 2.938] (**) | |-->Monitor "<default monitor>"
[ 2.939] (==) No monitor specified for screen "Default Screen Section".
Using a default monitor configuration.
[ 2.939] (==) Automatically adding devices
[ 2.939] (==) Automatically enabling devices
[ 2.939] (==) Automatically adding GPU devices
[ 2.939] (==) Max clients allowed: 256, resource mask: 0x1fffff
[ 2.941] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
[ 2.941] Entry deleted from font path.
[ 2.944] (==) FontPath set to:
/usr/share/fonts/X11/misc,
/usr/share/fonts/X11/100dpi/:unscaled,
/usr/share/fonts/X11/75dpi/:unscaled,
/usr/share/fonts/X11/Type1,
/usr/share/fonts/X11/100dpi,
/usr/share/fonts/X11/75dpi,
built-ins
[ 2.944] (==) ModulePath set to "/usr/lib/xorg/modules"