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Serial Port configuration in RHEL

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  • N Nimika

    how will I get to know wo is accessing that device?
    how can I add the user to the group which you have specified.

    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by
    #10

    @Nimika The user using your application needs access right for /dev/ttyS0.
    If you execute the command @SGaist provided you you will see who has access. Check which group is set for that device. Then add yourself to this group (see /etc/group file).

    https://forum.qt.io/topic/113070/qt-code-of-conduct

    N 1 Reply Last reply
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    • jsulmJ jsulm

      @Nimika The user using your application needs access right for /dev/ttyS0.
      If you execute the command @SGaist provided you you will see who has access. Check which group is set for that device. Then add yourself to this group (see /etc/group file).

      N Offline
      N Offline
      Nimika
      wrote on last edited by
      #11

      @jsulm Hey thanks!
      I am getting this after writing the calling function ls -la /dev/ttyS0:
      crw-rw----. 1 root dialout 4, 64 Oct 7 10:35 /dev/ttyS0

      What does it mean?

      jsulmJ 1 Reply Last reply
      0
      • N Nimika

        @jsulm Hey thanks!
        I am getting this after writing the calling function ls -la /dev/ttyS0:
        crw-rw----. 1 root dialout 4, 64 Oct 7 10:35 /dev/ttyS0

        What does it mean?

        jsulmJ Offline
        jsulmJ Offline
        jsulm
        Lifetime Qt Champion
        wrote on last edited by
        #12

        @Nimika That means that user root and group dialout have read/write access, nobody else have any access.
        So you either start your app as root, or (much better) add the user you're using (hopefully not root) to the group dialout.

        https://forum.qt.io/topic/113070/qt-code-of-conduct

        1 Reply Last reply
        0
        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #13

          NEVER EVER use root like that. All the more when developing. It's bad practice and doing so you're opening a gaping security hole.

          Add your normal user to the dialout group and be done with it.

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

          N 1 Reply Last reply
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          • N Offline
            N Offline
            Nimika
            wrote on last edited by
            #14

            Thankyou both of you.
            Please tell me how to add my normal user to the dialout group?
            What is dialout group?

            mrjjM jsulmJ 2 Replies Last reply
            1
            • K Offline
              K Offline
              kuzulis
              Qt Champions 2020
              wrote on last edited by
              #15

              QIODevice::OpenMode mode = QIODevice::ReadOnly | QIODevice::Unbuffered;

              Did you read documentation? QIODevice::Unbuffered it is unsupported mode.

              N 1 Reply Last reply
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              • K kuzulis

                QIODevice::OpenMode mode = QIODevice::ReadOnly | QIODevice::Unbuffered;

                Did you read documentation? QIODevice::Unbuffered it is unsupported mode.

                N Offline
                N Offline
                Nimika
                wrote on last edited by
                #16

                @kuzulis Yeah I made it as comment.

                1 Reply Last reply
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                • N Nimika

                  Thankyou both of you.
                  Please tell me how to add my normal user to the dialout group?
                  What is dialout group?

                  mrjjM Offline
                  mrjjM Offline
                  mrjj
                  Lifetime Qt Champion
                  wrote on last edited by mrjj
                  #17

                  @Nimika

                  • Please tell me how to add my normal user to the dialout group?
                    sudo usermod -a -G dialout theuser

                  • What is dialout group?
                    Its a predefined group found in many distros.
                    From old times it was used to allowed modems
                    to make connection etc. ( ie allow the user to connect to the internet :)

                  So often the system has this group and any user in it, have access to /dev/ttySX

                  N 1 Reply Last reply
                  1
                  • N Nimika

                    Thankyou both of you.
                    Please tell me how to add my normal user to the dialout group?
                    What is dialout group?

                    jsulmJ Offline
                    jsulmJ Offline
                    jsulm
                    Lifetime Qt Champion
                    wrote on last edited by
                    #18

                    @Nimika You really should learn how user/groups and access rights management is working on UNIX/Linux.

                    https://forum.qt.io/topic/113070/qt-code-of-conduct

                    1 Reply Last reply
                    1
                    • N Offline
                      N Offline
                      Nimika
                      wrote on last edited by
                      #19

                      @jsulm Actually my system is Red Hat Enterprise Linux based so it is different to use its commands.

                      1 Reply Last reply
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                      • mrjjM mrjj

                        @Nimika

                        • Please tell me how to add my normal user to the dialout group?
                          sudo usermod -a -G dialout theuser

                        • What is dialout group?
                          Its a predefined group found in many distros.
                          From old times it was used to allowed modems
                          to make connection etc. ( ie allow the user to connect to the internet :)

                        So often the system has this group and any user in it, have access to /dev/ttySX

                        N Offline
                        N Offline
                        Nimika
                        wrote on last edited by
                        #20

                        @mrjj Thank you !! let me add it now and search whether it will work or not.....

                        mrjjM 1 Reply Last reply
                        0
                        • N Nimika

                          @mrjj Thank you !! let me add it now and search whether it will work or not.....

                          mrjjM Offline
                          mrjjM Offline
                          mrjj
                          Lifetime Qt Champion
                          wrote on last edited by mrjj
                          #21

                          @Nimika
                          Np. as far as I can see it's the same for Red Hat with ttySX access, so there is
                          tons on google on the topic on allowing user X to read and write to /dev/ttSxxx
                          stuff.
                          http://ithelpblog.com/os/linux/bashandscripts/howto-add-user-to-group-on-linux-redhat-rhel-centos-fedora/

                          1 Reply Last reply
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                          • SGaistS SGaist

                            NEVER EVER use root like that. All the more when developing. It's bad practice and doing so you're opening a gaping security hole.

                            Add your normal user to the dialout group and be done with it.

                            N Offline
                            N Offline
                            Nimika
                            wrote on last edited by
                            #22

                            @SGaist Can I use serial ports to any user other than root?

                            mrjjM 1 Reply Last reply
                            0
                            • N Nimika

                              @SGaist Can I use serial ports to any user other than root?

                              mrjjM Offline
                              mrjjM Offline
                              mrjj
                              Lifetime Qt Champion
                              wrote on last edited by mrjj
                              #23

                              @Nimika
                              Hi
                              Any user can be granted access to /dev/X devices.
                              Often it is done via the dialout group as its already assigned to serial devices such as ttyS0 and
                              any user that is member of that group can use it.
                              so often
                              sudo adduser TheUserName dialout
                              and and reboot is all that is needed.
                              Adding user to group might have slightly different syntax on RH but concept and rights are 100% the same.:)
                              http://websistent.com/fix-serial-port-permission-denied-errors-linux/

                              N jsulmJ 2 Replies Last reply
                              0
                              • mrjjM mrjj

                                @Nimika
                                Hi
                                Any user can be granted access to /dev/X devices.
                                Often it is done via the dialout group as its already assigned to serial devices such as ttyS0 and
                                any user that is member of that group can use it.
                                so often
                                sudo adduser TheUserName dialout
                                and and reboot is all that is needed.
                                Adding user to group might have slightly different syntax on RH but concept and rights are 100% the same.:)
                                http://websistent.com/fix-serial-port-permission-denied-errors-linux/

                                N Offline
                                N Offline
                                Nimika
                                wrote on last edited by
                                #24

                                @mrjj Thanks let me try it.

                                1 Reply Last reply
                                0
                                • mrjjM mrjj

                                  @Nimika
                                  Hi
                                  Any user can be granted access to /dev/X devices.
                                  Often it is done via the dialout group as its already assigned to serial devices such as ttyS0 and
                                  any user that is member of that group can use it.
                                  so often
                                  sudo adduser TheUserName dialout
                                  and and reboot is all that is needed.
                                  Adding user to group might have slightly different syntax on RH but concept and rights are 100% the same.:)
                                  http://websistent.com/fix-serial-port-permission-denied-errors-linux/

                                  jsulmJ Offline
                                  jsulmJ Offline
                                  jsulm
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #25

                                  @mrjj @Nimika Just a note: after adding currently logged on user to a group you do not have to reboot (its not Windows :-)) - just log out and log in again.

                                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                                  N 1 Reply Last reply
                                  0
                                  • jsulmJ jsulm

                                    @mrjj @Nimika Just a note: after adding currently logged on user to a group you do not have to reboot (its not Windows :-)) - just log out and log in again.

                                    N Offline
                                    N Offline
                                    Nimika
                                    wrote on last edited by
                                    #26

                                    @jsulm Thank you!!
                                    But still in my case maybe RHEL is not allowing any other user to add in dialout group.

                                    mrjjM jsulmJ 2 Replies Last reply
                                    0
                                    • N Nimika

                                      @jsulm Thank you!!
                                      But still in my case maybe RHEL is not allowing any other user to add in dialout group.

                                      mrjjM Offline
                                      mrjjM Offline
                                      mrjj
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #27

                                      @Nimika said in Serial Port configuration in RHEL:

                                      RHEL is not allowing any other user to add in dialout group.

                                      cant you just use sudo in front?

                                      1 Reply Last reply
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                                      • N Nimika

                                        @jsulm Thank you!!
                                        But still in my case maybe RHEL is not allowing any other user to add in dialout group.

                                        jsulmJ Offline
                                        jsulmJ Offline
                                        jsulm
                                        Lifetime Qt Champion
                                        wrote on last edited by
                                        #28

                                        @Nimika RHEL works like any other Linux distribution. To add a user to a group you need to be root. You can either login as root, or just enter su in a terminal window enter your root password and then add the user to the group. su is used to become root in a shell (you need root password).
                                        @mrjj I think on RHEL sudo is usually not used, so sudo will probably not work (as far as I know, I could be wrong as I use Ubuntu).

                                        https://forum.qt.io/topic/113070/qt-code-of-conduct

                                        N mrjjM 2 Replies Last reply
                                        0
                                        • jsulmJ jsulm

                                          @Nimika RHEL works like any other Linux distribution. To add a user to a group you need to be root. You can either login as root, or just enter su in a terminal window enter your root password and then add the user to the group. su is used to become root in a shell (you need root password).
                                          @mrjj I think on RHEL sudo is usually not used, so sudo will probably not work (as far as I know, I could be wrong as I use Ubuntu).

                                          N Offline
                                          N Offline
                                          Nimika
                                          wrote on last edited by
                                          #29

                                          @jsulm
                                          Yeah I did all possibilities which I think can be done on RHEL.
                                          By the way Thanks a lot for your all kind replies. :)

                                          jsulmJ 1 Reply Last reply
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