stackbiz's questions

I want to use regex for checking only three allowed characters: "[0-9]" and "." and "/".

Note: The test case is an ipv4/ipv6 address but I don't want to check the number in the range [0-255], I only want to check allowed characters in the input variable.

I use "|" as the "or" expression, and combine all the three allowed characters with "|", and finally add "+" in the last for make sure at less one allowed character must exist in the input variable.

Here is the test bash script:

test_ipv4_address="127.0.0.1/24"
test_wrong_ipv4_address="127.0.0.1#24"
test_ipv6_address="::1/128"

allowed_characters='([0-9]|\.|\/)+'

[[ "$test_ipv4_address" =~ $allowed_characters ]] && echo "yes, $test_ipv4_address is allowed"
[[ "$test_wrong_ipv4_address" =~ $allowed_characters ]] && echo "yes, $test_wrong_ipv4_address is allowed"
[[ "$test_ipv6_address" =~ $allowed_characters ]] && echo "yes, $test_ipv6_address is allowed"

Here is the output:

yes, 127.0.0.1/24 is allowed
yes, 127.0.0.1#24 is allowed
yes, ::1/128 is allowed

Here is the expected output:

yes, 127.0.0.1/24 is allowed

What's wrong in my regex? And how to fix?

I found the set default background color code from @user313992's answer:

On xterm-like terminal emulators:

This sets the background to a light green without having to clear the screen:

printf %b '\e]11;#ccffcc\a'

It works. But how to set the default foreground color in Bash shell in a similar manner? Something like:

printf %b '???(default_foreground_color)???'

And, where to find the related information about the \e]11; code for the background color and the respective ??? code for the foreground color?

I want to stored all command args in an array but it only works when all args have no any (*).

Here is a test without using array:

mkdir -p /tmp/hello
echo "hello" > /tmp/hello/hello.txt
echo "world" > /tmp/hello/world.txt

mkdir -p /tmp/world

# This cp command is success
cp /tmp/hello/* /tmp/world

Now convert the cp command into my_array:

mkdir -p /tmp/hello
echo "hello" > /tmp/hello/hello.txt
echo "world" > /tmp/hello/world.txt

mkdir -p /tmp/world

declare -a my_array=()
my_array[0]="cp"
my_array[1]="/tmp/hello/*"
my_array[2]="/tmp/world"

# Run the command and it will fail
"${my_array[@]}"

Here is the error:

cp: cannot stat '/tmp/hello/*': No such file or directory

Is it possible for using (*) in the my_array? What's the correct syntax for implementing the 'cp /tmp/hello/* /tmp/world' with my_array?

Update:

There is a problem from @choroba's answoer, The $count and $sedond_item will be wrong:

mkdir -p /tmp/hello
echo "hello" > /tmp/hello/hello.txt
echo "world" > /tmp/hello/world.txt

mkdir -p /tmp/world

my_array=(cp)
my_array+=(/tmp/hello/*)
my_array+=(/tmp/world)

count=${#my_array[@]}
printf "%s\n" "count is: $count"

sedond_item="${my_array[1]}"
printf "%s\n" "second item is: $sedond_item"

Here is the output of @choroba's answoer:

count is: 4
second item is: /tmp/hello/hello.txt

But the $count and $sedond_item are correct in my original array:

mkdir -p /tmp/hello
echo "hello" > /tmp/hello/hello.txt
echo "world" > /tmp/hello/world.txt

mkdir -p /tmp/world

declare -a my_array=()
my_array[0]="cp"
my_array[1]="/tmp/hello/*"
my_array[2]="/tmp/world"

count=${#my_array[@]}
printf "%s\n" "count is: $count"

sedond_item="${my_array[1]}"
printf "%s\n" "second item is: $sedond_item"

Here is the output of original array:

count is: 3
second item is: /tmp/hello/*

I found the setfacl from this link:

https://stackoverflow.com/questions/39397548/how-to-give-non-root-user-in-docker-container-access-to-a-volume-mounted-on-the

sudo setfacl -m u:$(id -u):rwx -R /some/folder

But it will set all file permissions into rwx which is different from my requirement.

Here is the test folder:

rm -rf /test
mkdir -p /test/hello/world

echo "hello" > /test/hello.txt

echo "hi" > /test/hi.sh
chmod 755 /test/hi.sh

echo "foo" > /test/foo.sh
chmod 400 /test/foo.sh

echo "bar" > /test/bar.sh
chmod 700 /test/bar.sh

Here is the file permissions:

# ls -l /test

-rwx------ 1 root root    4 Jun  1 12:20 bar.sh
-r-------- 1 root root    4 Jun  1 12:20 foo.sh
drwxr-xr-x 3 root root 4096 Jun  1 12:20 hello
-rw-r--r-- 1 root root    6 Jun  1 12:20 hello.txt
-rwxr-xr-x 1 root root    3 Jun  1 12:20 hi.sh

I want to grant user 1234 the same permission as root:

sudo setfacl -m u:1234:(???) -R /test

Here is the expected permission for user 1234 (not changing the owner here, just use 1234 in here for explaining the detail permissions as the same as user root):

# ls -l /test

-rwx------ 1 1234 root    4 Jun  1 12:20 bar.sh
-r-------- 1 1234 root    4 Jun  1 12:20 foo.sh
drwxr-xr-x 3 1234 root 4096 Jun  1 12:20 hello
-rw-r--r-- 1 1234 root    6 Jun  1 12:20 hello.txt
-rwxr-xr-x 1 1234 root    3 Jun  1 12:20 hi.sh

How to write this sudo setfacl -m u:1234:(???) -R /test?

Here are the docker layers I want to implement: https://stackoverflow.com/questions/31222377/what-are-docker-image-layers

I want to mount a folder from host to docker with:

docker run \
-v /path/to/host/large_size_folder:/var/large_size_folder \
my_docker \
/bin/bash -c "rm -rf /var/large_size_folder/file1 && echo "hello" > /var/large_size_folder/file2"

Because the size of /path/to/host/large_size_folder is very large that I don't want to copy it to the docker image. So I use -v to mount it to the docker image.

And then, I run the docker and use bash to add/modify/delete files inside the "/var/large_size_folder".

But this action will also add/modify/delete files from host.

Is it possible to make any modification in the docker layer only without affecting the host directory when running /bin/bash -c "rm -rf /var/large_size_folder/file1 && echo "hello" > /var/large_size_folder/file2" inside the docker container?

The stackexchange link says "it is not possible to login to the account using a password", but the baeldung link says "anyone can log in to the account without any password".

The stackexchange link:

Both "!" and "!!" being present in the password field mean it is not possible to login to the account using a password.

As it can be read from the documentation of RHEL-4, the "!!" in the shadow-password field means the account of a user has been created, but not yet given a password. The documentation states (possibly erroneously) that until being given an initial password by a sysadmin, it is locked by default.

The baeldung link:

4. !! in /etc/shadow’s Password Field

   Another symbol that we may encounter in the password field of the /etc/shadow file is the two exclamation points. !! indicates that someone has created a user account but has not given it a password. Therefore, anyone can log in to the account without any password, which is a serious risk.

Which is correct for Ubuntu system?

I'm trying to check if a package is installed or not.

Here is a link for finding all packages with "deinstall" status: dpkg --get-selections shows packages marked "deinstall"

But I can't find any packages with "deinstall" from my running Ubuntu system.

What command can be used to make a "installed" package become the "deinstall" for testing purpose?

I'm trying to get the installed version of systemd in the following command, but it returns all lines contain the keyword "systemd".

# dpkg -l | grep " systemd "

ii  gnome-logs                                       42.0-1                                                           amd64        viewer for the systemd journal
ii  libsystemd0:amd64                                249.11-0ubuntu3.12                                               amd64        systemd utility library
ii  systemd                                          249.11-0ubuntu3.12                                               amd64        system and service manager
ii  systemd-container                                249.11-0ubuntu3.12                                               amd64        systemd container/nspawn tools

How to make it return only the following line:

# dpkg -l | grep "__the_rule_for_systemd_"

ii  systemd                                          249.11-0ubuntu3.12                                               amd64        system and service manager

And then, I can use awk to get the version:

# dpkg -l | grep "__the_rule_for_systemd_" | awk '{print $3}'

Here is the expected output:

249.11-0ubuntu3.12

How to write the "__the_rule_for_systemd_" for grep or is there any other command can get the installed version of systemd?

Note:

# package_name="systemd"
# dpkg -l | grep " $package_name "

The "__the_rule_for_systemd_" should also work on other packages, it should be able to get any package by that rule, not just only for "systemd".

Here is the unmount method for unmounting all previously mounted folders:

https://unix.stackexchange.com/questions/61885/how-to-unmount-a-formerly-chrootd-filesystem

I use the following command to mount the /sys and /dev to the chroot from the Ubuntu host:

cd /path/to/chroot/
mount -t sysfs /sys sys
mount -o bind /dev dev

If I delete the /sys and /dev inside the chroot without unmounting first:

chroot /path/to/chroot
rm -rf /sys
rm -rf /dev

Will it delete everything in the host system and then cause damage to the host system?

I found the following link for changing file types application:

https://superuser.com/questions/21626/ubuntu-change-the-default-program-used-to-open-a-type-of-file

Here is the command for associating the file type "application/pdf" with the "kde-kpdf.desktop" :

$xdg-mime query default application/pdf
AdobeReader.desktop
$xdg-mime default kde-kpdf.desktop application/pdf
$xdg-mime query default application/pdf
kde-kpdf.desktop

I just want to double-click the "*.pdf" and then open with "kde-kpdf.desktop",

but I want to hide the "kde-kpdf.desktop" from the Ubuntu desktop applications list as shown below (I downloaded the image from Internet, it doesn't contain the kde-kpdf.desktop icon in it):

Is it possible for hiding the specified *.desktop file from Ubuntu Applications List UI? How to hide the desktop but still allowing double-click the file-type to open with that application?

Here is the original nvidia-container-toolkit.list from GitHub:

https://nvidia.github.io/libnvidia-container/stable/deb/nvidia-container-toolkit.list

deb https://nvidia.github.io/libnvidia-container/stable/deb/$(ARCH) /
#deb https://nvidia.github.io/libnvidia-container/experimental/deb/$(ARCH) /

Here is the document from Nvidia:

https://docs.nvidia.com/datacenter/cloud-native/container-toolkit/latest/install-guide.html

curl -fsSL https://nvidia.github.io/libnvidia-container/gpgkey | sudo gpg --dearmor -o /usr/share/keyrings/nvidia-container-toolkit-keyring.gpg \
  && curl -s -L https://nvidia.github.io/libnvidia-container/stable/deb/nvidia-container-toolkit.list | \
    sed 's#deb https://#deb [signed-by=/usr/share/keyrings/nvidia-container-toolkit-keyring.gpg] https://#g' | \
    sudo tee /etc/apt/sources.list.d/nvidia-container-toolkit.list

I have tried to add the "signed-by" manually, and then replace the "$(ARCH)" with "amd64" or " amd64":

deb [signed-by=/usr/share/keyrings/nvidia.gpg] https://nvidia.github.io/libnvidia-container/stable/deb/amd64 /

or 

deb [signed-by=/usr/share/keyrings/nvidia.gpg] https://nvidia.github.io/libnvidia-container/stable/deb/ amd64 /

But the "apt-get update" failed with the following error:

E: Malformed line 1 in source list /etc/apt/sources.list.d/nvidia-container-toolkit.list (type)
E: The list of sources could not be read.

Here is the echo $(ARCH) in Ubuntu:

# echo $(ARCH)
ARCH: command not found

What's the correct form of "nvidia-container-toolkit.list"?

Update:

If I did not replace the $(ARCH), the error is still the same. I think the original nvidia document is wrong.

Update 2:

The problem may relate to the "$(ARCH)", what's $(ARCH) in the nvidia?

When logging into the Ubuntu system, the login user is "root".

And then, I want to execute some bash script on behalf of the "non_root":

root@test_pc:~# echo $USER
root
root@test_pc:~# sudo -E -u non_root -g non_root -H /bin/bash -c "echo $USER"
root
root@test_pc:~# 

But the output is still "root", in other words, the command is still execute under "root" user instead of "non_root".

Here is the expected output:

root@test_pc:~# sudo -E -u non_root -g non_root -H /bin/bash -c "echo $USER"
non_root
root@test_pc:~#

Here is the real operation:

sudo -E -u non_root -g non_root -H /bin/bash -c "systemctl --user disable pulseaudio.service"

But got the following error:

Failed to connect to bus: Operation not permitted (consider using --machine=<user>@.host --user to connect to bus of other user)

How to execute any bash command as "non_root" when logged in with "root" user?

I want to set the windows size in bash script but I don't know which command is used to set the windows size.

When open the File Browser in Ubuntu Desktop, and then change the Windows size of the File Browser by dragging the bottom-right corner of File Browser, and then close the Window and reopen the File Browser, the windows size will change to the last size.

Here is the picture of File Browser:

Where is the config file for storing the last updated windows size of File Browser? Or what bash command can be used to set the windows size?

According to the following launchpad, the ubuntu-22.04.2 has already released 15 hours ago.

https://launchpad.net/ubuntu/+milestone/ubuntu-22.04.2

Milestone information
Project:
    Ubuntu
Series:
    Jammy
Version:
    ubuntu-22.04.2
Expected:
    15 hours ago   
Active:
    Yes. Drivers can target bugs and blueprints to this milestone. 

But the following link still says the latest is 22.04.1:

https://ubuntu.com/download/desktop

Ubuntu 22.04.1 LTS
The latest LTS version of Ubuntu, for desktop PCs and laptops. LTS stands for long-term support — which means five years of free security and maintenance updates, guaranteed until April 2027.

Where to download ubuntu-22.04.2 as stated in the launchpad?

I want to use sed to replace the XML tag on bash.

Here is the example xml content for testing:

<xml-content>
<validation>
<timeout>2880</timeout>
<subject>example</subject>
<required>true</required>
</validation>
</xml-content>

I want to replace the tag validation:

<validation>
<timeout>2880</timeout>
<subject>example</subject>
<required>true</required>
</validation>

with the new tag other-tag:

<other-tag>
<hello/>
<more>false</more>
</other-tag>

Here is the final expected result:

<xml-content>
<other-tag>
<hello/>
<more>false</more>
</other-tag>
</xml-content>

How to do it with a single command line sed?

I have setup both archiva and httpd on Ubuntu 22.04 for testing.

Apache Archiva version: 2.2.9
Apache HTTP Server: 2.4.52

The VirtualHost configuration:

<VirtualHost _default_:443>
    ProxyPass "/test/" "http://192.168.1.1:8080/"
    ProxyPassReverse "/test/" "http://192.168.1.1:8080/"
</VirtualHost>

HTTP Server URL: https://my.example.com/test/
Archiva Server URL: http://192.168.1.1:8080/

When using Firefox to open the http://192.168.1.1:8080/ directly, then the whole Archiva UI can show up normally.

When using Firefox to open the https://my.example.com/test/, Firefox can show the title as "Apache Archiva" but the Web Content not showing up, it only shows the "Loading"...

What's missing in the VirtualHost for making the Archiva to work with Reverse Proxy?

Update: Here is the view source from Firefox:

view-source:https://my.example.com/test/

<html>
  <head>
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <link rel="stylesheet" href="css/jquery.fileupload-ui.css"/>
    <link rel="stylesheet" href="css/jqueryFileTree.css"/>
    <link rel="stylesheet" href="css/jquery-ui-1.9.2.custom.min.css"/>
    <link rel="stylesheet" href="css/select2-3.2.css"/>
    <link rel="stylesheet" href="css/typeahead.js-bootstrap.0.9.3.css"/>
    <link rel="stylesheet" href="css/bootstrap.2.2.2.css">
    <link rel="stylesheet" href="css/archiva.css">
    <link rel="shortcut icon" href="favicon.ico"/>
    <link rel="stylesheet" href="css/prettify.css"/>

    <script type="text/javascript" src="js/jquery-1.11.1.min.js"></script>
    <script type="text/javascript" src="js/jquery-ui-1.10.4.min.js"></script>
    <script type="text/javascript" src="js/sammy.0.7.4.js"></script>
    <script type="text/javascript" data-main="js/archiva/archiva.js" src="js/require.min.2.1.11.js"></script>

    <title>Apache Archiva</title>

  </head>
...

view-source:https://my.example.com/test/js/archiva/archiva.js

requirejs(['jquery','jquery.tmpl','jquery.ui','i18n','sammy','startup','utils','domReady!','archiva.main','archiva.cookie-information'], function () {
        loadi18n(function () {
          $.ajax({
            url: "restServices/archivaUiServices/runtimeInfoService/archivaRuntimeInfo/"+usedLang(),
            dataType: 'json',
            success:function(data){
              window.archivaDevMode=data.devMode;
              window.archivaJavascriptLog=data.javascriptLog;
              window.archivaRuntimeInfo=data;

              window.cookieInformation=mapCookieInformation(data.cookieInformation);

              require(['sammy','jquery','jquery.ui','i18n','jquery.tmpl','archiva.main','utils','domReady!'],function () {
                  startArchivaApplication();
                  $("#loadingDiv").hide();
                  drawQuickSearchAutocomplete();
              })
            }
          })
        });
      });  


  

From the view source, Firefox can get the correct html content from Archiva 8080 server, but it can't activate the js function "loadi18n", the "$("#loadingDiv").hide();" is not executed at all.

The "js/archiva/archiva.js" in Archiva can't work as expected in reverse proxy mode for unknown reason.

Testing the ping on ubuntu 22.04:

Host A IPv6: 1111:1111:1111:1111:1111:1111:1111:1111
Host B IPv6: 2222:2222:2222:2222:2222:2222:2222:2222

Host A:

Now execute a ping from Host A with the following bash command:

root@host_a:~# ping -6 2222:2222:2222:2222:2222:2222:2222:2222

Host B:

The iptables dropped some packets and log it to the file:

Dec 7 18:21:52 host_b kernel: [ 988.996335] dropped output: IN= OUT=ens33 SRC=192.168.1.1 DST=192.168.2.1 LEN=83 TOS=0x00 PREC=0x00 TTL=64 ID=52289 PROTO=UDP SPT=41151 DPT=53 LEN=63 UID=113 GID=118

Dec 7 18:21:52 host_b kernel: [ 988.998359] dropped output: IN= OUT=ens33 SRC=2222:2222:2222:2222:2222:2222:2222:2222 DST=1111:1111:1111:1111:1111:1111:1111:1111 LEN=72 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=136 CODE=0

Dec 7 18:21:53 host_b kernel: [ 990.001075] dropped output: IN= OUT=ens33 SRC=2222:2222:2222:2222:2222:2222:2222:2222 DST=1111:1111:1111:1111:1111:1111:1111:1111 LEN=72 TC=0 HOPLIMIT=255 FLOWLBL=0 PROTO=ICMPv6 TYPE=136 CODE=0

From the first log line, there is a UID and GID info:

UID=113 GID=118

We can find the user by using this method:

root@host_b:~# cat /etc/passwd | grep 113

But for the 2nd and 3rd lines there is no any UID or GID in the log.

Question:

How to find out which program is sending out the following network packets?

PROTO=ICMPv6 TYPE=136 CODE=0

Note: Based on the iptables log, this "Unknown" program accepts incoming ICMPv6 packets and then send out outgoing ICMPv6 packets, but iptables can't log the UID and GID of that "Unknown" program when the packet is drooped by rule.

Here is the value set in Ubuntu 22.04:

root@test:~# cat /proc/sys/kernel/sysrq
176

I can't find the value from this link:

https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html

What does it mean?