showkey's questions

I can talk with my friend and watch images each other in skype,that is to say that built-in microphone and speaker can be used in skype on my Ubuntu OS.

There is no wechat's official version running on Linux,wechat only can run on android,iPhone,mac,windows. Some geeker use docker to build wechat in Linux this way:

docker pull bestwu/wechat
xhost +
docker run -d --name wechat --device /dev/snd \
           -v /tmp/.X11-unix:/tmp/.X11-unix \
           -v $HOME/WeChatFiles:/WeChatFiles \
           -e DISPLAY=unix$DISPLAY \
           -e XMODIFIERS=@im=fcitx \
           -e QT_IM_MODULE=fcitx \
           -e GTK_IM_MODULE=fcitx \
           -e AUDIO_GID=`getent group audio | cut -d: -f3` \
           -e GID=`id -g` \

Now to input wechat in terminal,i can use it to input text ,i can hear friend's voice ,but he can't hear my voice,no image can be showed on screen(the image can be shown in cheese and skype), the built-in microphone and camera can't be used in wechat.How can fix it?

The possible way :

electron-wechat

Installed ,can't be start successfully.

wechat on web

Show all sound card in my pc.

pacmd list-sources |grep  name:
    name: <alsa_output.pci-0000_00_1b.0.analog-stereo.monitor>
    name: <alsa_input.pci-0000_00_1b.0.analog-stereo>

Now to capture audio playing via alsa_output.pci-0000_00_1b.0.analog-stereo.monitor.

ffmpeg -f pulse -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor \
       /tmp/out.mkv

I encounter error info:

Queue input is backward in time
    Last message repeated 3 times
[matroska @ 0x562e991d5e00] Non-monotonous DTS in output stream 0:0; previous: 4550, current: 4507; changing to 4550. This may result in incorrect timestamps in the output file.

How to fix it?

The below gif's dimensions are 600*800. Height is 800 pixels, so there's a lot of blank space at the bottom I want to remove.

This was saved as old.gif:

file old.gif 
old.gif: GIF image data, version 89a, 600 x 800

Resized with convert command:

convert old.gif -coalesce temp.gif
convert -size 600x800 temp.gif -resize 600x400! new.gif

！ means ignore aspect ratio, do not keep aspect ratio unchanged.
Here's the result:

The new file new.gif is deformed.

How can I resize the gif without deforming it?

My try with -crop argument.

convert old.gif -crop 600x400+0+0 new.gif

How to remove the blank region in new.gif?

The blank white region is obvious in firefox. convert old.gif -crop 600x400+0+0 new.gif can't remove the blank white region in new.gif.

Using the repage argument will remove the blank white region, but it makes the gif more blurred.

convert old.gif -crop 600x400+0+0 -trim  +repage  new.gif    

cat  /home/upload.sh  
/usr/bin/scp -P 22   /home/material.gz   root@remote_ip:/home
date  >>  /var/log/upload.log

Setting for upload.service

cat  /etc/systemd/system/upload.service
[Unit]
Description=upload files into my vps 
Before=shutdown.target  reboot.target
Requires=network-online.target
After=network.target 

[Service]
ExecStart=/bin/true
ExecStop=/bin/bash /home/upload.sh  

[Install]
WantedBy=multi-user.target

The script can upload file into my vps before shutdown.

The strange thing is the upload service's log.

journal -u upload 
Apr 23 12:54:50 localhost systemd[1]: Stopping upload files into my vps...
Apr 23 12:55:13 localhost systemd[1]: Stopped upload files into my vps.
Apr 23 12:55:19 localhost systemd[1]: Started upload files into my vps.
Apr 23 12:55:19 localhost systemd[1]: Starting upload files into my vps...

Why it is not such as following order?

Apr 23 12:54:50 localhost systemd[1]: Stopping upload files into my vps...
Apr 23 12:55:13 localhost systemd[1]: Stopped upload files into my vps.
Apr 23 12:55:19 localhost systemd[1]: Starting upload files into my vps...
Apr 23 12:55:19 localhost systemd[1]: Started upload files into my vps.

Only differ in the last two lines,why?
Which result in this kind of log info?

Do as George Udosen say:Try this in the service file [Unit] Requires=network-online.target After=network.target network-online.target.

It is no use at all.

lshw -C  cpu
  *-cpu                     
       product: Intel(R) Xeon(R) CPU E3-1275 v5 @ 3.60GHz
       vendor: Intel Corp.
       vendor_id: GenuineIntel
       physical id: 1
       bus info: cpu@0
       width: 64 bits
       capabilities: fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp x86-64 constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf cpuid_faulting pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch ida arat epb pln pts dtherm hwp hwp_noitfy hwp_act_window hwp_epp invpcid_single tpr_shadow vnmi flexpriority ept vpid fsgsbase bmi1 hle avx2 smep bmi2 erms invpcid rtm rdseed adx xsaveopt xsavec xgetbv1 xsaves

I want to upload a file to my dropbox when my pc is shutting down.

sudo vim  /etc/systemd/system/upload.service
[Unit]
Description=upload files into dropbox
Before=network.target shutdown.target  reboot.target
Requires=network-online.target

[Service]
ExecStop=/bin/true
ExecStart=/bin/bash  /home/upload.sh 
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target

And the upload.sh script.

cd  /home
curl -X POST https://content.dropboxapi.com/2/files/upload \
            --header "Authorization: Bearer xxxx" \
            --header "Dropbox-API-Arg:  {\"path\":\"/test.txt\",\"mode\":{\".tag\":\"overwrite\"}}" \
            --header "Content-Type: application/octet-stream" \
            --data-binary @"test.txt"

bash upload.sh can executed successfully,and test.txt file uploaded into my dropbox.

sudo systemctl enable upload service  

To reboot my pc.

sudo journalctl -u upload 

Apr 13 23:58:52 localhost systemd[1]: Started upload files into dropbox.
Apr 13 23:58:52 localhost systemd[1]: Starting upload files into dropbox...
Apr 13 23:58:52 localhost bash[117]: % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
Apr 13 23:58:52 localhost bash[117]: Dload  Upload   Total   Spent    Left  Speed
Apr 13 23:58:52 localhost bash[117]: 0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0curl: (6) Could not resolve host: content.dropboxapi.com; Un
Apr 13 23:58:52 localhost systemd[1]: upload.service: main process exited, code=exited, status=6/NOTCONFIGURED
Apr 13 23:58:52 localhost systemd[1]: Unit upload.service entered failed state.
Apr 13 23:58:52 localhost systemd[1]: upload.service failed.

Some DNS error Could not resolve host: content.dropboxapi.com result in upload.service failed.

I have added Requires=network-online.target in upload.service,how to make DNS parser resolve the host at my pc's shutdowning time?

Here is my cpu part of info(omitted unnecessary).

cat /proc/cpuinfo
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 60
model name  : Intel(R) Celeron(R) CPU G1840 @ 2.80GHz
stepping    : 3
microcode   : 0x19
cpu MHz     : 2800.000
cache size  : 2048 KB
physical id : 0
siblings    : 2
core id     : 0
cpu cores   : 2

There two cpus in my pc.
top command can display cpus usage as a whole.
How to display cpu1 usage and cpu2 usage respectively?

To make my app autorun during reboot.

sudo vi /etc/systemd/system/app.service

[Unit]
Description=app
After=network.target

[Service]
ExecStart=/usr/bin/python /usr/local/bin/app  
[Install]
WantedBy=multi-user.target


sudo systemctl daemon-reload
sudo systemctl enable app.service

Now my app autorun during reboot.
I want to make my app write all output info into /var/log/app.log.
Here is what i do.
1.sudo touch /var/log/app.log
2. to change ExecStart only.

ExecStart=/usr/bin/python /usr/local/bin/app   > /var/log/app.log 2>&1

App can run but no log written into /var/log/app.log.
Root will execute the app.
It's proof here.

ps aux|grep  app
root       246  0.0  3.8  56052 10056 ?        Ss   00:57   0:00 /usr/bin/python /usr/local/bin/app   > /var/log/app.log 2>&1

Why root has no permission to write log into /var/log/app.log?

To change ExecStart statement into

ExecStart=/bin/sh -c '/usr/bin/python /usr/local/bin/app   > /var/log/app.log 2>&1'  

Problem solved.
1.Why root no permission to write log into /var/log/app.log?
2.What does /bin/bash -c mean in service unit?

I found that more pts can be created this way.

1. To reboot into text mode-tty1

2. to input startx to jump into gui mode.
   To enter terminal in the gui mode started from tty1 to inupt.

     tty    
     /dev/pts/0  
   

this gui is pts/0

3. to input ctrl+alt+f2 to jump into
   another text mode-tty2
4. to input startx to jump into gui mode, this gui is pts/1.

To enter terminal in the gui mode started from tty2 to inupt

    tty
    /dev/pts/1  

Now two gui modes can be created.
How to know how many tty and pts are running at the same time on my pc?

Every gui program--include virtual terminal in gui is the client(or say slave) of x-server(or say x window system) ,so it was called pesudo terminal slave.

Muru give me many new knowledge,maybe there is a wrong expression in muru's explaination.

In my opinion,the proper sentence would be that:
but that's an application program in X server started from the tty1, but also a pts.

Please see the discuss here on what is pts/0 and (:0.0) in linux when typing who am i

From the knowledge,i draw my conclusion.

It not only an X server started from the tty1, but also a pts.

Apache was installed, www-data is owner of /var/www/html/wp.
I miss the key, and want to alter it now.

sudo cat /etc/shadow |grep www-data
www-data:*:17053:0:99999:7:::

To change it into www-data::17053:0:99999:7::: and save it.

su www-data
Password: 

To input enter, no character inputed.

su: Authentication failure

How to alter the password for www-data user?

I see that xterm - a popular terminal emulator designed for the X Window System - is used in my DE, lxde.

echo $TERM
xterm

Now I switch into tty1 with ctrlaltF1.

echo $TERM
linux

Does this mean that a terminal emulator program named linux is using in tty1?

In "Text-based user interface" Wikipedia's article, when talk to text based user interface, the first sentence is:

Not to be confused with Command-line interface.

I can't find some differences between CLI (Command Line Interface) and TUI (Textual User Interface).

Is that true or not?

There are two lines in /etc/privoxy/config:

logdir /var/log/privoxy
logfile logfile

The command curl -x "127.0.0.1:8118" https://www.yahoo.com has been executed many times.

cat /var/log/privoxy/logfile 

Why is there nothing in the log file /var/log/privoxy/logfile?

An error info occur when to execute apt-get update .

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used.

GPG error: http://download.virtualbox.org jessie InRelease: The following
signatures couldn't be verified because the public key is not available: 
NO_PUBKEY A2F683C52980AECF

I found an answer:

gpg --keyserver  key_server_name  --recv-keys  A2F683C52980AECF
gpg --armor --export A2F683C52980AECF| apt-key add -

There are two pool.sks-keyservers.net and keys.gnupg.net among many public key servers, are they equal?

gpg --keyserver  pool.sks-keyservers.net  --recv-keys  A2F683C52980AECF
gpg --keyserver  keys.gnupg.net  --recv-keys  A2F683C52980AECF

Do the two commands take same effect?

aria2c -S  /home/se.torrent

Files:    
idx|path/length    
===+===========================================================================
1|./test.mkv        
 |283MiB (297,429,086)        

---+---------------------------------------------------------------------------

I want to save the downloaded file as ok.mkv in /tmp.

aria2c -d   /tmp  -o  ok.mkv    /home/se.torrent

The downloaded name can't be changed into /tmp/ok.mkv ,it is still
/tmp/test.mkv when the command executed.

In manual of aria2c -h ,there is no strings such as:
NOTE: You cannot specify a file name for Metalink or BitTorrent downloads.

In the console to input dpkg-reconfigure locales,a gui jump out ,i select en_HK.UTF-8 as my target ,click enter.

dpkg-reconfigure locales
Generating locales (this might take a while)...
en_HK.UTF-8... done

How to automate the whole process into one command ?

When you open your Ubuntu, many English words are used. For example, accessories, education, graphics, internet, office, other, sound, video, system tools, preferences, run, and log out will all appear in the GUI.

How can I get a list of all English words used in the Ubuntu GUI?

I want a list of all English words so I can translate them into Chinese, to create a glossary for Ubuntu: a guide in Chinese to English-language Ubuntu terminology. This would work as a mini dictionary: a two-columns file with English on the left and Chinese on the right.

It is a joke to write the whole thing just from looking at the words on the GUI. I want a smart way to do the task. Is there a list of all the words used by Ubuntu?

Typing by hand as I come across words in the GUI is a foolish way to get the task done.

1. Copy out all English words one-by-one from the GUI when the locale is set to en_us.
2. Copy out all Chinese words one-by-one from the GUI when the locale is set to zh.
3. Put them together in one file, with English on the left and Chinese on the right.

Is there a smarter way to do this?
Which character in my /usr/lib/locale/locale-archive ?

apt-get --purge remove nginx
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  nginx-common nginx-full
Use 'apt-get autoremove' to remove them.
The following packages will be REMOVED:
  nginx*
0 upgraded, 0 newly installed, 1 to remove and 23 not upgraded.
After this operation, 101 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 213649 files and directories currently installed.)
Removing nginx (1.6.2-5) ...
root@pengsir:/home/debian8# dpkg -l nginx
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-=================================
un  nginx          <none>       <none>       (no description available)
root@pengsir:/home/debian8# find / -name 'nginx'
/usr/sbin/nginx
/usr/share/nginx
/etc/nginx
/etc/ufw/applications.d/nginx
/etc/logrotate.d/nginx
/etc/init.d/nginx
/etc/default/nginx
/var/lib/nginx
/var/log/nginx

apt-get autoremove
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
  nginx-common nginx-full
0 upgraded, 0 newly installed, 2 to remove and 23 not upgraded.
After this operation, 1,339 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 213645 files and directories currently installed.)
Removing nginx-full (1.6.2-5) ...
Removing nginx-common (1.6.2-5) ...
Processing triggers for man-db (2.7.0.2-5) ...

find / -name 'nginx'
/etc/nginx
/etc/ufw/applications.d/nginx
/etc/logrotate.d/nginx
/etc/init.d/nginx
/etc/default/nginx
/var/log/nginx

The files such as /usr/sbin/nginx .... are all related to nginx,i think that nginx don't be removed completely at all.
When we sya completely uninstall package_name,does it mean to delete all the configuration files related the package_name?
How to remove all the files with some command efficiently?
Please do not tell to do with find / -name 'nginx' | rm -rf......

I have installed both apache2 and nginx as web server.
I found that it is a strange thing that apache2 logo will be still displayed in the firefox when service apache2 stop executed and nginx logo can't be displayed in the firefox when service nginx start executed.

Whatever you stop apache2 or start nginx ,the apache2 debian default page always be display in my firefox.

The config file /etc/apache2/sites-available/000-default.conf of apache2 is as below:

<VirtualHost *:8080>
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/html
    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

The config file /etc/nginx/sites-available/default of nginx is as below:

server {
    listen       8080;
    server_name  127.0.0.1;
    root /var/www/html;
    index index.php index.html index.htm index.nginx-debian.html;

    location / {
            try_files $uri $uri/ =404;
    }

    error_page 404 /404.html;
    error_page 500 502 503 504 /50x.html;

    location = /50x.html {
            root /var/www/html;
    }

    location ~ \.php$ {
            try_files $uri =404;
            fastcgi_pass unix:/var/run/php5-fpm.sock;
            fastcgi_index index.php;
            fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
            include fastcgi_params;
    }
}

In my os ,

ls /var/www/html
index.nginx-debian.html  index.html

The index.html is a apache2 debian logo,everytime 127.0.0.1:8080 executed, index.html was called no matter apache2 or nginx ,apache2 debian logo was displayed.
Problem solved.

I have installed nginx .

dpkg -l nginx
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend 
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-=================================
ii  nginx          1.6.2-5      all          small, powerful, scalable web/pro

Everytime i go to install other package ,the error info displayed.

dpkg: warning: files list file for package 'nginx-full' missing; assuming package has no files currently installed
dpkg: warning: files list file for package 'nginx-common' missing; assuming package has no files currently installed

How to fix it ,not to let the info displayed again when to install other package?

The ed2k is : ed2k://|file|test.iso|1643802624|A3058CE4F2AD70356D07AAA5|/

I want to save the iso in /home .

How can i write command to download the ed2k into /home/test.iso with amule or mldonkey?