Tag Archives: Operation and maintenance

[Solved] Invalid signature error for ROS repository while trying to do sudo apt-get update

After installing ROS in Ubuntu system, the apt-get update command reports an error:

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://packages.ros.org/ros/ubuntu bionic InRelease: The following signatures were invalid: EXPKEYSIG F42ED6FBAB17C654 Open Robotics <[email protected]>
W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/InRelease  Could not resolve 'dl.google.com'
W: Failed to fetch http://packages.ros.org/ros/ubuntu/dists/bionic/InRelease  The following signatures were invalid: EXPKEYSIG F42ED6FBAB17C654 Open Robotics <[email protected]>
W: Failed to fetch http://packages.microsoft.com/repos/code/dists/stable/InRelease  Could not resolve 'packages.microsoft.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.

Solution:
we have to re-add the mentioned GPG key to the system by using command below

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys F42ED6FBAB17C654

[Solved] kafka Startup Error: Fatal error during KafkaServer startup

Kafka startup error

Solution:

server.properties file

listeners=PLAINTEXT://:9092(Note that there is no IP address in this line, I just had a problem with the IP)
advertised.listeners=PLAINTEXT://114.115.20.100:9092 (need to let go of the comment)

ERROR: Invalid subnet : invalid CIDR address: [How to Fix]

Error reporting configuration:

networks:
  test_220:
    driver: bridge
    ipam:
      config:
        - subnet: 172.40.0.0/24
        - gateway: 172.40.0.1

Modified configuration:

networks:
  test_220:
    driver: bridge
    ipam:
      config:
        - subnet: 172.40.0.0/24
          gateway: 172.40.0.1

Just remove the “-” in front of the gateway

[Solved] Some index files failed to download.They have been ignored, or old ones used instead

sudo apt-get updateerror:

Err:1 http://ppa.launchpad.net/wireshark-dev/stable/ubuntu bionic InRelease
  Temporary failure resolving 'ppa.launchpad.net'
Err:2 http://security.ubuntu.com/ubuntu bionic-security InRelease
  Temporary failure resolving 'security.ubuntu.com'
Err:3 http://archive.ubuntu.com/ubuntu bionic InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Err:4 http://archive.ubuntu.com/ubuntu bionic-updates InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Err:5 http://archive.ubuntu.com/ubuntu bionic-backports InRelease
  Temporary failure resolving 'archive.ubuntu.com'
Reading package lists... Done
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-backports/InRelease  Temporary failure resolving 'archive.ubuntu.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease  Temporary failure resolving 'security.ubuntu.com'
W: Failed to fetch http://ppa.launchpad.net/wireshark-dev/stable/ubuntu/dists/bionic/InRelease  Temporary failure resolving 'ppa.launchpad.net'
W: Some index files failed to download. They have been ignored, or old ones used instead.

Use Ping www.google.comtest the network. If it appears: Ping: www.google.com: temporary failure in name resolution is a network problem,

Solution:

first

sudo vim /etc/systemd/resolved.conf

Modify DNS as follows:

[Resolve]
DNS=8.8.8.8
#FallbackDNS=
#Domains=
#LLMNR=no
#MulticastDNS=no
#DNSSEC=no
#Cache=yes
#DNSStubListener=yes

Modify the following configuration file

vim /etc/resolv.conf

Add the following:

nameserver 8.8.8.8

Then restart:

reboot

Just update the source after restart:

sudo apt-get update

[Solved] Error getting ssh command ‘exit 0‘ : ssh command error:

docker-machine Create Certificate Stuck
docker-machine –debug create -d hyperv –hyperv-virtual-switch “Default Switch” docker-machine
Hint
https://github.com/minishift/minishift/issues/2722

Hi,
the only way for me to get around this was to disable the Windows 10
built-in OpenSSH Client, via Windows Features.
After that minishift used its internal ssh client and proceeded.
Unfortunately i am running into another issue after that, where the
control-plane pods are not starting and the minishift deployment fails,
since the API access times out.
Would be inteeresting to see if you get the same once you deal with the SSH
stuff
Am Fr., 30. Nov. 2018 um 12:15 Uhr schrieb denisjc7 <
[email protected]>:
…
Hi,
@LW81 https://github.com/LW81 I am experiencing the same issue on
basically the same configurations as yours. Did you find a solution?Thank
you
—
You are receiving this because you were mentioned.
Reply to this email directly, view it on GitHub
<#2722 (comment)>,
or mute the thread
https://github.com/notifications/unsubscribe-auth/ATAFNHdE_fyUXANlW2bT8vzeFZ8Un2Erks5u0RNggaJpZM4WHLXu

Solution:
Through [Settings] => [Applications] => [Optional Applications
Uninstall Windows 10 built-in OpenSSH Client
After using the built-in ssh, it runs successfully

[Solved] Rsync synchronization Error: @ERROR: Unknown module xxx

Scenario:

Push files from server a to server B

Error message

@ERROR: Unknown module ‘xxx’

rsync error: error starting client-server protocol (code 5) at main. c(1649) [sender=3.1.6]

Finally, it is found that the default configuration file of Rsync is rsyncd.com under/etc.conf instead of the file rsyncd. In the/etc/rsyncd/folder.conf

Solution 1: directly configure /etc/rsyncd.conf file, the operation steps are omitted.

Solution 2:

(1) Modify VIM /lib/SYSTEMd/system/rsyncd.service,

The following is the configuration content

[Unit]
Description=fast remote file copy program daemon
ConditionPathExists=/etc/rsyncd/rsyncd.conf

[Service]
EnvironmentFile=/etc/sysconfig/rsyncd
ExecStart=/usr/bin/rsync --config=/etc/rsyncd/rsyncd.conf  --daemon --no-detach "$OPTIONS"

[Install]
WantedBy=multi-user.target

(2) Reload the background process and restart the Rsync service to synchronize.

systemctl daemon-reload

systemctl restart rsyncd

Related commands:

Systemctl daemon reload daemon

Systemctl restart rsyncd restart synchronization service

Systemctl start rsyncd# start

Systemctl stop rsyncd stop

systemctl status rsyncd. Service view Rsync status

PS aux | grep Rsync | viewing process

[Solved] error during connect: This error may indicate that the docker daemon is not running

Because the shortcut key of my screenshot tool is Ctrl+q , and the shortcut key of docker desktop exit is also Ctrl+q, when I press Ctrl+q, docker desktop exits, and then when I enter the docker command in the console,

burst this line of error

error during connect: This error may indicate that the docker daemon is not running.: Get "http://%2F%2F.%2Fpipe%2Fdocker_engine/v1.24/containers/json": open //./pipe/docker_engine: The system cannot find the file specified.

Solution:
reopen docker desktop

when the color of the icon in the lower-left corner is the same as that shown in the picture, it proves that docker operates normally
then I go to CMD and enter the docker command

to see that there is no error

Ubuntu install and compile OpenCV3.4.0 fatal error: dynlink_nvcuvid.h: No such file or directory #include ＜dynlink_nv

Problems encountered

fatal error: dynlink_nvcuvid.h: No such file or directory #include <dynlink_nvcuvid.h>

Solution
Add: -dbuild_opencv_cudacodec=OFF

mkdir build
cd build
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D BUILD_TIFF=ON -DBUILD_opencv_cudacodec=OFF ..

sudo make -j12
sudo make install

Problems encountered

[ WARN:0] cvCreateFileCaptureWithPreference: backend FFMPEG doesn't support legacy API anymore.

Solution

install opencv3.4.0

It must be 3.4.0, others 3.4 X is wrong
3.4.0 download address https://codeload.github.com/opencv/opencv/tar.gz/refs/tags/3.4.0
Then install the extension package of OpenCV 3.4.0, download address, https://codeload.github.com/opencv/opencv_contrib/tar.gz/refs/tags/3.4.0

[Solved] Ubuntu Server 18.4 System /etc/sudoers: syntax error near line 32

Cause: Because the /etc/sudoers file was previously edited with a problem, the default Ubuntu system could not use sudo to raise power after saving, and could not use root privileges causing a big problem; the default Ubuntu system root was not allowed to log in, and the root login password had not been set before; sadly, it could not be modified by directly logging into the root account.

The problem is in /etc/sudoers: syntax error near line 32 of the sudoers file.

Solution.

1. open two shell windows with the normal user “ubuntu”.

2, in the first ssh session execute “echo $$” and write down the PID

3, in the second ssh session, execute “pkttyagent –process PID”.

4. Execute “pkexec visudo” in the first ssh session and then enter the password in the second ssh session. This will give you access to the /etc/sudoers file, then you will know the error line and modify the data.

5. Use the nano editor for editing by default.

1、Execute "Ctrl+O" #Save
2, after the implementation of "Ctrl + O", the output will be "File Name to Write sudoers.tmp", in tmp after the implementation of the carriage return * 
3、Execute "Ctrl+X "* #Exit

At this time, when you open the shell link, you will not report an error when using sudo and Su rights raising behavior;

[Solved] Error: listen EADDRINUSE: address already in use :::5000

Port occupied

Solution: check the process occupying the port in the terminal. PID: sudo lsof – I: 5000;

Re terminate the process: Kill – 9 {PID};

sudo lsof -i :5000；
// get the progress pid
kill -9 {pid};// Enter the obtained pid, such as 10086, without {}

[Solved] Linux Error: ENOSPC: System limit for number of file watchers

Problem:
System: Ubuntu 18
problem scenario: when using react scaffold to write a case, the command NPM start is unsuccessful, and an error: enospc: system limit for number of file watchers occurs.

Solution:
error: enospc: system limit for number of file watchers error is that the system of the file monitor has a limit and reaches the default upper limit, so the limit needs to be increased
you can use the instruction $cat/proc/sys/FS/inotify/max_user_watch to see

root@:~$ cat /proc/sys/fs/inotify/max_user_watch
es
524288

New instructions can be set for temporary limit increase:

$ sudo sysctl fs.inotify.max_user_watches=524288
$ sudo sysctl -p

Permanent increase limit

$ echo fs.inotify.max_user_watches = 524288 | sudo tee -a /etc/sysctl.conf 
$ sudo sysctl -p

Linux Drive Error: Error: function declaration isn’t a prototype

1. The problem is as follows:

2. The solutions are as follows:

When linux driver writes a function, when there is no formal parameter, void type data should be passed in.

static int led_init(void)
{
    int ret = 0;

    return ret; 
}

ProgrammerAH

Programmer Guide, Tips and Tutorial