Qt app work on boot ubuntu

JonB

@asisisyah said in Qt app work on boot ubuntu:

qt.qpa.xcb: could not connect to display

And sure enough that is the reason, as we suggested. I don't know how you expect a UI program to find and connect to a display when it is run from boot rather than from the user's desktop.

Strat by setting environment variable QT_DEBUG_PLUGINS to value 1. Then you will get possibly more helpful diagnostic output. How you set that variable when running from boot the way you do I do not know. It may be enough to just set the environment variable in the very first line of your code, before you create the QApplication. I cannot recall if that is early enough or whether it has to be set before the executable is even launched, but worth a try.

asisisyah

@asisisyah
yes i set it , but problem is that i used /dev/mem file for gpio , this is permitted and i dont know any solition. when my program start on boot or after the desktop , doesent mater for me, its not running because /dev/mem is permitted.. so i use sudo ..

SGaist

@asisisyah the usual way is to add the proper rights for the user to access the device. It's usually done through adding the user to a specific group.

asisisyah

@asisisyah
i tried but i dont make it.
maybe i must change gpiolib. can you suggest a library or easyes way for control. i use Qt and jetson orin nano and c++, because i use rubberazer jetgipio library . if i dont use jetgpio myApp did starting perfectly s on boot.

Thank you all

SGaist

@asisisyah what did you try exactly ?

Did you add the user that will start the application to the kmem group ?

asisisyah

@asisisyah
my user name is nvidia its add in group called nvidia.
i want say again
i have a program , its working in terminal with command sudo ./myApp.. i want start automaticly when system is open. thats all . its not to be that very hard. but i dont make it.
thank you all.

SGaist

@asisisyah you know that a user can be part of several groups ?

asisisyah

@asisisyah
i am sorry but no. i am newbe for linux.
please explain.
i must make it my project is end . everything is okey but its not start on automaticly. please explain step by step or i am goingto crazy.
regards.

SGaist

@asisisyah a quick search of "Linux add group to user" would have been quicker. See for example here.

asisisyah

@asisisyah
i did add many group my username (nvidia)

nvidia@nvidia-desktop:~/Desktop$ groups
nvidia adm sudo audio video render gdm docker weston-launch gpio jtop
nvidia@nvidia-desktop:~/Desktop$ id
uid=1001(nvidia) gid=1001(nvidia) groups=1001(nvidia),4(adm),27(sudo),29(audio),44(video),103(render),130(gdm),132(docker),996(weston-launch),999(gpio),1002(jtop)
nvidia@nvidia-desktop:~/Desktop$ groups nvidia
nvidia : nvidia adm sudo audio video render gdm gpio weston-launch docker jtop
nvidia@nvidia-desktop:~/Desktop$ getent group
root:x:0:
daemon:x:1:
bin:x:2:
sys:x:3:
adm:x:4:syslog,{USERNAME},nvidia
tty:x:5:syslog
disk:x:6:
lp:x:7:
mail:x:8:
news:x:9:
uucp:x:10:
man:x:12:
proxy:x:13:
kmem:x:15:
dialout:x:20:
fax:x:21:
voice:x:22:
cdrom:x:24:
floppy:x:25:
tape:x:26:
sudo:x:27:{USERNAME},nvidia
audio:x:29:pulse,{USERNAME},nvidia
dip:x:30:
www-data:x:33:
backup:x:34:
operator:x:37:
list:x:38:
irc:x:39:
src:x:40:
gnats:x:41:
shadow:x:42:
utmp:x:43:
video:x:44:{USERNAME},gdm,nvidia
sasl:x:45:
plugdev:x:46:
staff:x:50:
games:x:60:
users:x:100:
nogroup:x:65534:
input:x:101:
kvm:x:102:
render:x:103:{USERNAME},nvidia
ssh:x:104:
dhcpd:x:105:
netdev:x:106:
systemd-timesync:x:107:
systemd-journal:x:108:
systemd-network:x:109:
systemd-resolve:x:110:
messagebus:x:111:
rdma:x:112:
i2c:x:113:
tss:x:114:
crontab:x:115:
lpadmin:x:116:
bluetooth:x:117:
ssl-cert:x:118:
whoopsie:x:119:
geoclue:x:120:
scanner:x:121:saned
pulse:x:122:
pulse-access:x:123:
avahi-autoipd:x:124:
saned:x:125:
rtkit:x:126:
colord:x:127:
avahi:x:128:
nm-openvpn:x:129:
gdm:x:130:{USERNAME},nvidia
syslog:x:131:
gpio:x:999:nvidia
trusty:x:998:
crypto:x:997:
weston-launch:x:996:{USERNAME},nvidia
{USERNAME}:x:1000:
nvidia:x:1001:
systemd-coredump:x:995:
debug:x:994:
docker:x:132:nvidia
fwupd-refresh:x:133:
jtop:x:1002:nvidia
nvidia@nvidia-desktop:~/Desktop$

ChrisW67

@asisisyah said in Qt app work on boot ubuntu:

yes i set it , but problem is that i used /dev/mem file for gpio ,

This is my Ubuntu:

$ ls -l /dev/mem
crw-r----- 1 root kmem 1, 1 Jan 14 06:53 /dev/mem

So, your process can read and write (rw-) /dev/mem if it is run as root (i.e. via sudo) , and read-only (r--) if your process is run by a user in the kmem group, and no access at all (---) for anyone else. This restriction is for a good reason.

I will guess that your nvidia user is not in the kmem group; no standard Ubuntu user is.

$ id -a chrisw
uid=1000(chrisw) gid=1000(chrisw) groups=1000(chrisw),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),122(lpadmin),133(lxd),134(sambashare),136(docker),137(wireshark)

and service accounts are generally far more restricted:

$ id -a dnsmasq
uid=111(dnsmasq) gid=65534(nogroup) groups=65534(nogroup)

asisisyah

my /dev/mem ls -l
$ ls -l /dev/mem
crw-rw----- 1 root nvidia 1, 1 Jan 13 21:13 /dev/mem

and please what i must do. if you explain i think i do it.
step by step.

thank you all

SGaist

@asisisyah said in Qt app work on boot ubuntu:

my /dev/mem ls -l
$ ls -l /dev/mem
crw-rw----- 1 root nvidia 1, 1 Jan 13 21:13 /dev/mem

and please what i must do. if you explain i think i do it.
step by step.

thank you all

Were these the original rights of the device ?

asisisyah

@asisisyah
No , its not. Originally that root:root
My user name : nvidia

SGaist

@asisisyah what distribution are you running on your device ?

asisisyah

@asisisyah
first of all thank you so much everyone.
i made a "starter.sh" file... than echo nvidia | sudo -S ./myApp ...
than start it with startUp Application .

its worked. no problem just now

thank you so much everyone