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#1 2018-05-05 13:51:49

bitfreak
Member
Registered: 2018-05-02
Posts: 15

[solved] start of lightdm fails with a blinking screen

Hello,

I've got a problem with using lightdm on a clean install with xfce. After installing lightdm and enabling the lightdm.service by

pacman -S lightdm lightdm-gtk-greeter
systemctl enable lightdm.service

my system now starts with my display blinking (the monitor turns on and of and a black screen is shown when activated). From there I could not change to a TTY-Console, so I have to reboot my PC over the power-button.

I've already described the behaviour in a german thread on Archlinux.de, but couldn't get the solution. So I hope that someone else could have a look at this problem.

Here are the related logfiles:
/var/log/lightdm/lightdm.conf
/var/log/lightdm/seat0-greeter.log
/var/log/lightdm/x-0.log
/var/log/Xorg.0.log

If you need additional information don't hesitate to ask.

Last edited by bitfreak (2018-05-11 17:26:27)

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#2 2018-05-05 14:22:10

seth
Member
Registered: 2012-09-03
Posts: 49,992

Re: [solved] start of lightdm fails with a blinking screen

stat /var/lib/lightdm/.Xauthority

Removing the file might be sufficient but this could be a false positive and the actual error is some crashing greeter, taking down the X11 server and "irritating" the lightdm core, so please also look up coredumpctl and/or the journal.

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#3 2018-05-05 19:06:20

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

Hello seth,

the file "/var/lib/lightdm/.Xauthority" doesn't exist, so I expect lightdm tries to create it, but couldn't.

The command "coredumpctl" mentions that there is no codedump.

With "journalctl" I could track the behaviour of the start of lightdm (triggered by "systemctl start lightdm" as root). The output could be seen here.

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#4 2018-05-05 19:14:53

seth
Member
Registered: 2012-09-03
Posts: 49,992

Re: [solved] start of lightdm fails with a blinking screen

Mai 05 20:46:33 LIFEBOOK-ARCH kernel: caller _nv000788rm+0xe4/0x1c0 [nvidia] mapping multiple BARs
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: ------------[ cut here ]------------
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: Bad or missing usercopy whitelist? Kernel memory exposure attempt detected from SLUB object 'nvidia_stack_t' (offset 11864, size 3)!
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: WARNING: CPU: 2 PID: 429 at mm/usercopy.c:81 usercopy_warn+0x7e/0xa0
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: Modules linked in: 8021q mrp fuse nvidia(PO) snd_hda_codec_realtek intel_powerclamp arc4 gpio_ich ath9k iTCO_wdt ath9k_common coretemp iTCO_vendor_support ath9k_hw ath kvm_intel broadcom bcm_phy_lib snd_hda_codec_generic snd_hda_codec_hdmi pcspkr mac80211 kvm irqbypass uvcvideo intel_cstate intel_uncore cfg80211 tg3 snd_hda_intel mousedev videobuf2_vmalloc videobuf2_memops drm rfkill videobuf2_v4l2 videobuf2_common psmouse videodev snd_hda_codec ptp joydev input_leds snd_hda_core media pps_core libphy mei_me mei evdev battery fujitsu_laptop sparse_keymap snd_hwdep snd_pcm snd_timer snd rtc_cmos intel_ips shpchp intel_agp intel_gtt agpgart lpc_ich i2c_i801 soundcore ac mac_hid acpi_cpufreq ip_tables x_tables ext4 crc16 mbcache jbd2 fscrypto hid_generic usbhid hid sr_mod cdrom sd_mod serio_raw
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  atkbd libps2 ahci libahci firewire_ohci sdhci_pci libata cqhci sdhci firewire_core ehci_pci ehci_hcd crc32c_intel led_class scsi_mod crc_itu_t mmc_core usbcore usb_common i8042 serio
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: CPU: 2 PID: 429 Comm: Xorg Tainted: P           O     4.16.6-1-ARCH #1
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: Hardware name: FUJITSU LIFEBOOK NH570/FJNB209, BIOS Version 1.06  05/31/2010
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: RIP: 0010:usercopy_warn+0x7e/0xa0
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: RSP: 0018:ffffb4dc409b3bb0 EFLAGS: 00010286
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: RAX: 0000000000000000 RBX: ffff92f92365de58 RCX: 0000000000000001
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: RDX: 0000000080000001 RSI: ffffffff9ae680bc RDI: 00000000ffffffff
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: RBP: 0000000000000003 R08: 0000000000000094 R09: 0000000000000364
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: R10: ffffffff9aea43b9 R11: 0000000000000001 R12: 0000000000000001
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: R13: ffff92f92365de5b R14: ffff92f92365de58 R15: ffff92f92365dea0
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: FS:  00007f715bae9940(0000) GS:ffff92f937d00000(0000) knlGS:0000000000000000
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: CR2: 00007f71528bf160 CR3: 0000000131f40006 CR4: 00000000000206e0
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: Call Trace:
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  __check_object_size+0x130/0x1a0
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  os_memcpy_to_user+0x21/0x40 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  _nv001372rm+0xa5/0x260 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? _nv004784rm+0x4eba/0x5500 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? _nv004331rm+0xec/0xf0 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? _nv004326rm+0xca/0x650 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? _nv015126rm+0x576/0x5c0 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? _nv000694rm+0x2e/0x60 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? _nv000789rm+0x5f5/0x8b0 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? _raw_spin_unlock_irqrestore+0x20/0x40
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? rm_ioctl+0x73/0x100 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? nvidia_ioctl+0x221/0x460 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? nvidia_frontend_ioctl+0x2d/0x60 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? nvidia_frontend_unlocked_ioctl+0x19/0x20 [nvidia]
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? do_vfs_ioctl+0xa4/0x630
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? __sb_end_write+0x42/0x60
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? vfs_write+0x131/0x1a0
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? SyS_ioctl+0x74/0x80
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? do_syscall_64+0x74/0x190
Mai 05 20:46:34 LIFEBOOK-ARCH kernel:  ? entry_SYSCALL_64_after_hwframe+0x3d/0xa2
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: Code: 48 c7 c0 81 23 e7 9a 48 0f 44 c2 41 50 51 41 51 48 89 f9 49 89 f1 4d 89 d8 4c 89 d2 48 89 c6 48 c7 c7 d8 23 e7 9a e8 42 aa e3 ff <0f> 0b 48 83 c4 18 c3 48 c7 c6 bc 80 e6 9a 49 89 f1 49 89 f3 eb 
Mai 05 20:46:34 LIFEBOOK-ARCH kernel: ---[ end trace 4e49e1760a7473bf ]---

Does it work w/ nouveau or the modesetting driver?

pacman -Qs nvidia
uname -a

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#5 2018-05-05 19:29:35

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

I've installed the proprietary nvidia graphic drivers.

# pacman -Qs nvidia
local/nvidia-340xx 340.106-32
    NVIDIA drivers for linux, 340xx legacy branch
local/nvidia-340xx-utils 340.106-1
    NVIDIA drivers utilities
local/xf86-video-nouveau 1.0.15-2 (xorg-drivers)
    Open Source 2D acceleration driver for nVidia cards
# uname -a
Linux LIFEBOOK-ARCH 4.16.6-1-ARCH #1 SMP PREEMPT Mon Apr 30 12:30:03 UTC 2018 x86_64 GNU/Linux

Please note that I could start the system directly by "startxfce4" or using Slim as loginmanager. So it seems to be a problem with lightdm or its dependencies.

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#6 2018-05-05 19:50:56

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

Could this forum thread and bug report be related to this behaviour?

I've fixed it going to /var/lib then "chown lightdm.lightdm lightdm/"

This doesn't work for me.

I also couldn't do the following solution, because there are no *.pacnew's files.

The solution was simply to merge all new *.pacnew's in /etc/lightdm smile

Last edited by bitfreak (2018-05-05 19:52:53)

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#7 2018-05-06 13:05:45

seth
Member
Registered: 2012-09-03
Posts: 49,992

Re: [solved] start of lightdm fails with a blinking screen

idk, let's see ;-)

stat /var/lib/lightdm
pacman -Qkk lightdm
id lightdm 
grep lightdm /etc/group /etc/passwd

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#8 2018-05-06 14:26:49

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

The output (I used "LC_ALL=C" to make the output in English):

# LC_ALL=C stat /var/lib/lightdm
  File: /var/lib/lightdm
  Size: 4096      	Blocks: 8          IO Block: 4096   directory
Device: 804h/2052d	Inode: 1836747     Links: 2
Access: (1770/drwxrwx--T)  Uid: (  620/ lightdm)   Gid: (  620/ lightdm)
Access: 2018-05-05 16:54:51.396712747 +0200
Modify: 2018-05-03 20:20:53.924463224 +0200
Change: 2018-05-03 20:20:53.924463224 +0200
 Birth: -
# LC_ALL=C pacman -Qkk lightdm
backup file: lightdm: /etc/lightdm/lightdm.conf (Modification time mismatch)
backup file: lightdm: /etc/lightdm/lightdm.conf (Size mismatch)
lightdm: 390 total files, 0 altered files
# LC_ALL=C id lightdm
uid=620(lightdm) gid=620(lightdm) groups=620(lightdm)
# LC_ALL=C grep lightdm /etc/group /etc/passwd
/etc/group:lightdm:x:620:
/etc/passwd:lightdm:x:620:620:Light Display Manager:/var/lib/lightdm:/sbin/nologin

And the current content of lightdm.conf. I've only removed the "#" in line "pam-service=lightdm" as suggested from another user.

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#9 2018-05-06 14:49:38

seth
Member
Registered: 2012-09-03
Posts: 49,992

Re: [solved] start of lightdm fails with a blinking screen

Let's see what happens if you remove the sticky bit:

sudo chmod -t /var/lib/lightdm

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#10 2018-05-06 15:10:19

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

I've executed "chmod -t /var/lib/lightdm" as root and started the the lightdm.service but nothing changed.

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#11 2018-05-06 15:25:18

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

I've noticed that I removed the sticky bit correctly but it reappears after the start of the lightdm.service .

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#12 2018-05-06 15:37:27

seth
Member
Registered: 2012-09-03
Posts: 49,992

Re: [solved] start of lightdm fails with a blinking screen

See /usr/lib/tmpfiles.d/lightdm.conf

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#13 2018-05-06 15:43:34

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

/usr/lib/tmpfiles.d/lightdm.conf

d /run/lightdm 0711 lightdm lightdm 0
d /var/cache/lightdm 0711 root lightdm -
d /var/lib/lightdm 1770 lightdm lightdm -
d /var/lib/lightdm-data 1770 lightdm lightdm -
d /var/log/lightdm 0711 root lightdm -

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#14 2018-05-06 15:49:05

seth
Member
Registered: 2012-09-03
Posts: 49,992

Re: [solved] start of lightdm fails with a blinking screen

I know what that file looks like :-)
It controls the permissions, so alter them there.

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#15 2018-05-06 16:00:48

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

I've already changed it like that:

d /run/lightdm 0711 lightdm lightdm 0
d /var/cache/lightdm 0711 root lightdm -
d /var/lib/lightdm 0770 lightdm lightdm -
d /var/lib/lightdm-data 0770 lightdm lightdm -
d /var/log/lightdm 0711 root lightdm -

executed

chmod -t /var/lib/lightdm
chmod -t /var/lib/lightdm-data

and started the lightdm.service . The sticky bit now doesn't change, but the problem stays the same.

Please have a look at this last change of the lightdm-package. There this file was changed, so the problem could be inside this change.

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#16 2018-05-06 16:55:18

loqs
Member
Registered: 2014-03-06
Posts: 17,196

Re: [solved] start of lightdm fails with a blinking screen

The lightdm tmpfiles.conf snippet as shipped by lightdm 1:1.26.0-1 works here @seth are you sure that is the cause?
Edit:
on this system /var/lib/lightdm/.Xauthority exists owner lightdm:lightdm

Last edited by loqs (2018-05-06 17:08:40)

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#17 2018-05-06 20:16:45

seth
Member
Registered: 2012-09-03
Posts: 49,992

Re: [solved] start of lightdm fails with a blinking screen

I've no idea what's the cause but apparently he's got trouble to write the Xauthority file for some reason (the idea was that there're multiple autority files written and lightdm lacks the rights to delete the interim one because of the sticky bit - apparently that's not the case)
Since the user/group IDs are fine as well i'm rather back to "the error is a false positive"

@bitfreak:

sudo -u lightdm touch /var/lib/lightdm/.Xauthority

a) does that work
b) does it have any impact?

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#18 2018-05-06 20:29:21

loqs
Member
Registered: 2014-03-06
Posts: 17,196

Re: [solved] start of lightdm fails with a blinking screen

I wonder about this from lightdm.log

[+0.01s] WARNING: Error getting user list from org.freedesktop.Accounts: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.Accounts was not provided by any .se$
[+0.01s] DEBUG: Loading user config from /etc/lightdm/users.conf
[+0.01s] DEBUG: User user added
[+0.97s] DEBUG: Got signal 15 from process 1

It differs on my system as it uses accountsservice but why is is getting a signal from process 1 the init system?
On this system (process 466 is X)

[+1.40s] DEBUG: Got signal 10 from process 446
[+1.40s] DEBUG: XServer 0: Got signal from X server :0
[+1.40s] DEBUG: XServer 0: Connecting to XServer :0

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#19 2018-05-06 20:47:07

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

seth wrote:

@bitfreak:

sudo -u lightdm touch /var/lib/lightdm/.Xauthority

a) does that work
b) does it have any impact?

I've already used this command as requested in the German thread. The output was:

sudo: stat konnte nicht auf /etc/sudoers angewendet werden: Permission denied
sudo: Keine gültige sudoers-Quelle gefunden, Programmende
sudo: Regelwerks-Plugin konnte nicht initialisiert werden
loqs wrote:

It differs on my system as it uses accountsservice but why is is getting a signal from process 1 the init system?

This was my use of the power-button, cause I couldn't stop this behavior otherwise. In an older logfile I got this.

Last edited by bitfreak (2018-05-06 21:59:10)

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#20 2018-05-06 20:54:08

loqs
Member
Registered: 2014-03-06
Posts: 17,196

Re: [solved] start of lightdm fails with a blinking screen

Pasting_pictures_and_code

For non-English locale users: Please prepend LC_ALL=C to posted commands so that the output will be in English.

What is the output of

LC_ALL=C stat /etc/sudoers

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#21 2018-05-06 21:20:14

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

loqs wrote:

Pasting_pictures_and_code

For non-English locale users: Please prepend LC_ALL=C to posted commands so that the output will be in English.

Sorry for that. Already know about it, but was too lazy, so I copied it.

loqs wrote:

What is the output of

LC_ALL=C stat /etc/sudoers
  File: /etc/sudoers
  Size: 3174      	Blocks: 8          IO Block: 4096   regular file
Device: 804h/2052d	Inode: 131306      Links: 1
Access: (0440/-r--r-----)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2018-05-05 14:27:18.953465826 +0200
Modify: 2018-01-21 20:06:16.000000000 +0100
Change: 2018-05-05 14:27:18.966799160 +0200
 Birth: -

Important note:
I've tested sddm on the same system and got a similar behavior.

pacman -S sddm
systemctl start sddm

There I've got a black screen.

So it seems that lightdm is not effected directly. With this in mind I have a question. I've installed my system with a personal installer-script, using the following commands to create the user and give him a password:

useradd -m -g users -s /bin/bash user
echo "user:$user_pwd" | chpasswd

Is that okay?

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#22 2018-05-06 21:51:15

loqs
Member
Registered: 2014-03-06
Posts: 17,196

Re: [solved] start of lightdm fails with a blinking screen

Is the user configured for sudo access or do you use su or login as root?
What is the output of

LC_ALL=C sudo -u lightdm touch /var/lib/lightdm/.Xauthority

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#23 2018-05-06 21:58:56

bitfreak
Member
Registered: 2018-05-02
Posts: 15

Re: [solved] start of lightdm fails with a blinking screen

loqs wrote:

Is the user configured for sudo access or do you use su or login as root?
What is the output of

LC_ALL=C sudo -u lightdm touch /var/lib/lightdm/.Xauthority
sudo: unable to stat /etc/sudoers: Permission denied
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin

And I've logged in as root on tty.

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#24 2018-05-06 22:12:09

loqs
Member
Registered: 2014-03-06
Posts: 17,196

Re: [solved] start of lightdm fails with a blinking screen

The output of

# LC_ALL=C su -s /usr/bin/bash lightdm touch
$ LC_ALL=C pacman -Qkk sudo
$ id -u user #check if the uid is somehow below 1000

Edit:
changed sudoers to sudo thanks seth

Last edited by loqs (2018-05-07 09:17:48)

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#25 2018-05-07 05:25:37

seth
Member
Registered: 2012-09-03
Posts: 49,992

Re: [solved] start of lightdm fails with a blinking screen

stat /usr/bin/sudo
stat /etc
stat /
mount
LC_ALL=C pacman -Qkk sudo # @loqs, there's no sudoers pacakge ;-)

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