Category: Linux

  • Connect to backend failed: connect to lsphp failed: 110

    Connect to backend failed: connect to lsphp failed: 110

    On a CloudLinux Server, websites stopped working with the error message “Service Unavailable”. On checking error_log in /usr/local/apache/logs, found following error message

    [Fri Jul 09 15:32:37.884950 2021] [lsapi:error] [pid 1639593:tid 47853204383488] [client 207.46.13.54:46915] mod_lsapi: [host ronnie.serverok.in] [req GET / HTTP/1.1] Connect to backend failed: connect to lsphp failed: 110

    The problem was due to the server got booted using the default CentOS kernel instead of CloudLinux Kernel.

    [root@server ~]# uname -a
Linux server.serverok.in 3.10.0-1062.9.1.el7.x86_64 #1 SMP Thu May 27 10:10:44 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
[root@server ~]#

    If you were using Cloudlinux kernel, “uname -a” command will show kernel with “lve” in the name. Example 3.10.0-962.3.2.lve1.5.56.el7.x86_64

    To see the list of kernels available, run

    awk -F\' '$1=="menuentry " {print i++ " =  "$2}' /etc/grub2.cfg

    Example

    [root@server ~]#  awk -F\' '$1=="menuentry " {print i++ " =  "$2}' /etc/grub2.cfg
0 =  CloudLinux (3.10.0-962.3.2.lve1.5.56.el7.x86_64) 7.9 (Boris Yegorov)
1 =  CloudLinux (3.10.0-1062.9.1.el7.x86_64) 7.9 (Boris Yegorov)
2 =  CloudLinux (3.10.0-962.3.2.lve1.5.27.el7.x86_64) 7.9 (Boris Yegorov)
3 =  CloudLinux (0-rescue-21361cf887984f57a840ce7ea6a3f75c) 7.9 (Boris Yegorov)
[root@server ~]#

    To set default kernel, run

    grub2-set-default 0

    This will set kernel entry to the first entry.

    Verify default kernel with

    grub2-editenv list

    Example

    [root@server ~]# grub2-editenv list
saved_entry=0
[root@server ~]#

    Reboot the server with

    reboot

    Once rebooted, verify the server is booted with CloudLinux kernel.

  • Linux tr command (translate)

    Linux tr command (translate)

    The tr command is used to translate text.

    Example

    root@ok:~# echo "serverok" | tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
SERVEROK
root@ok:~#

    You can also use

    root@ok:~# echo "serverok" | tr "a-z" "A-Z"
SERVEROK
root@ok:~#

    To change specific chars

    root@ok:~# echo "serverok" | tr "sok" "SOK"
ServerOK
root@ok:~#

    To delete char, use -d option

    root@ok:~# echo "serverok" | tr -d "ok"
server
root@ok:~#

    See Linux Commands

  • Skype public key is not available

    Skype public key is not available

    I have Ubuntu 20.04 computer with skype installed. When I update software using apt update, I get 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: https://repo.skype.com/deb stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 1F3045A5DF7587C3
W: Failed to fetch https://repo.skype.com/deb/dists/stable/InRelease  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 1F3045A5DF7587C3
W: Some index files failed to download. They have been ignored, or old ones used instead.

    To fix this error, delete the key

    sudo apt-key del 1F3045A5DF7587C3

    Add the key again with

    sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 1F3045A5DF7587C3

    Now you can update software with

    sudo apt update
sudo apt upgrade -y

    See Skype

  • lxc error Unable to fetch GPG key from keyserver

    lxc error Unable to fetch GPG key from keyserver

    When i create an lxc container on the Ubuntu server, I get an error

    root@instance-20210627-0830:~# lxc-create -t download -n ok
Setting up the GPG keyring
ERROR: Unable to fetch GPG key from keyserver
lxc-create: ok: lxccontainer.c: create_run_template: 1616 Failed to create container from template
lxc-create: ok: tools/lxc_create.c: main: 319 Failed to create container ok
root@instance-20210627-0830:~#

    To fix this, you can run

    export DOWNLOAD_KEYSERVER="keyserver.ubuntu.com"

    To make it permanent, add it to .bashrc

    vi ~/.bashrc

    At the end of the file, add

    export DOWNLOAD_KEYSERVER="keyserver.ubuntu.com"

    Method 2

    You can specify DOWNLOAD_KEYSERVER environment variable for the command with

    DOWNLOAD_KEYSERVER="keyserver.ubuntu.com" lxc-create -t download -n mycontainer -- -d ubuntu -r focal -a amd64

    Method 3

    Use –keyserver command line argument

    lxc-create -t download -n mycontainer -- -d ubuntu -r focal -a amd64 --keyserver hkp://keyserver.ubuntu.com

    See lxc

  • configure: error: Couldn’t find pcre.h, try installing the libpcre

    configure: error: Couldn’t find pcre.h, try installing the libpcre

    When installing PHP OAuth, I get the following error

    configure: error: Couldn't find pcre.h, try installing the libpcre development/headers package
ERROR: `/tmp/pear/temp/oauth/configure --with-php-config=/usr/bin/php-config' failed

    To fix, install libpcre3-dev

    apt install libpcre3-dev

    See Errors

  • CyberPanel FTP not working on Ubuntu Server

    CyberPanel FTP not working on Ubuntu Server

    On CyberPanel server, FTP was not working. I checked the server with “netstat -lntp” command. No service was listening on port 21. Started pure-ftpd with command

    systemctl start pure-ftpd-mysql

    To start pure-ftpd on boot, run 

    systemctl enable pure-ftpd-mysql

    Now FTP service started listening on port 21, but login to the FTP server failed with an error “Login authentication failed”.

    pure-ftpd on CyberPanel server uses MySQL authentication. We need to configure pure-ftpd to use the “users” table in “cyberpanel” database.

    Edit file

    vi /etc/pure-ftpd/db/mysql.conf

    In this file, you need to add MySQL login details

    MYSQLUser
MYSQLPassword
MYSQLDatabase   cyberpanel
MYSQLCrypt      md5

    If you don’t have a MySQL user, create one with

    GRANT ALL PRIVILEGES ON *.* TO 'ftpadmin'@'localhost' IDENTIFIED BY 'USER_PASSWORD_HERE' WITH GRANT OPTION;
GRANT PROXY ON ''@'' TO 'ftpadmin'@'localhost' WITH GRANT OPTION;

    Here is the example config

    MYSQLSocket      /var/run/mysqld/mysqld.sock
MYSQLUser       ftpadmin
MYSQLPassword   MYSQL_USER_PW_HERE
MYSQLDatabase   cyberpanel
MYSQLCrypt      md5
MYSQLGetPW      SELECT Password FROM users WHERE User='\L'
MYSQLGetUID     SELECT Uid FROM users WHERE User='\L'
MYSQLGetGID     SELECT Gid FROM users WHERE User='\L'
MYSQLGetDir     SELECT Dir FROM users WHERE User='\L'

    If you don’t have MySQL auth enabled, enable it with

    ln -s /etc/pure-ftpd/conf/MySQLConfigFile /etc/pure-ftpd/auth/30mysql

    Restart pure-ftp-mysql with

    systemctl restart pure-ftpd-mysql

    See CyberPanel

  • How to cut lines separated by multiple spaces?

    How to cut lines separated by multiple spaces?

    cut is a Linux command that can be used to cut a line of text with a specific delimiter. I want to cut lines separated by multiple spaces like

    cut multiple space

    Since the fields are separated by multiple spaces, I can’t just use cut -d’ ‘ command. What you can do is combine multiple spaces into one using tr command.

    tr -s ' '

    Here is the command I used to get all database name with Sleep connections

    mysqladmin processlist | grep "Sleep" | tr -s ' ' | cut -d' ' -f8

    Another solution is to use awk command.

    mysqladmin processlist | grep "Sleep" | awk '{print $8}'

    See cut

  • How to fix WordPress 404 error in Webuzo

    How to fix WordPress 404 error in Webuzo

    Webuzo hosting control panel has the option for selecting web servers Apache or Nginx. On a server using Nginx, after uploading the WordPress site and restoring the database, the website home page worked. When I clicked on any web page, I get a 404 Page not found error.

    To fix this, you need to add an extra configuration for Nginx. Login to Webuzo control panel.

    Webuzo Extra configuration

    Click on Extra Configuration.

    webuzo

    On this page, select the domain name that you need 404 error fixed. On Webservers dropdown select Nginx.

    Create a file permlink.conf on your computer with the following content

    try_files $uri $uri/ /index.php?$args;

    Browse and upload this file in the Webuzo control panel. This will fix the 404 error for the WordPress site.

    Webuzo will create a configuration file at

    /usr/local/apps/nginx/etc/conf.d/YOUR-DOMAIN.TLD/permlink.conf

  • How to install and use rdesktop

    rdesktop is an open-source client for connecting to windows using Windows Remote Desktop Services.

    To install rdesktop on CentOS/Fedora run

    yum install rdesktop

    To install rdesktop on Ubuntu/Debian servers, run

    apt install rdesktop

    To connect a server with rdesktop

    rdesktop -u administrator SERVER_IP

  • sshpass

    sshpass is used to non interactively log in to remote SSH server and execute commands. It can use a password from a file, environment variable, or from a command-line argument.

    To install sshpass on RHEL/CentOS, run

    yum install sshpass

    On Debian/Ubuntu

    apt install sshpass

    Example

    boby@sok-01:~$ sshpass ssh -o StrictHostKeyChecking=no -p 3333 [email protected] "uptime"
 02:16:14 up 470 days, 10:41,  0 users,  load average: 0.07, 0.04, 0.04
boby@sok-01:~$

    Take MySQL backup on a remote server

    sshpass ssh -o StrictHostKeyChecking=no -p 3333 [email protected] "mysqldump serverok_wp > /root/serverok_wp.sql"

    Command-line options for sshpass are

    root@sok-01:~# sshpass
Usage: sshpass [-f|-d|-p|-e] [-hV] command parameters
   -f filename   Take password to use from file
   -d number     Use number as file descriptor for getting password
   -p password   Provide password as argument (security unwise)
   -e            Password is passed as env-var "SSHPASS"
   With no parameters - password will be taken from stdin

   -P prompt     Which string should sshpass search for to detect a password prompt
   -v            Be verbose about what you're doing
   -h            Show help (this screen)
   -V            Print version information
At most one of -f, -d, -p or -e should be used
root@sok-01:~#

    To login to password using a password in the command line, use

    sshpass -p PASSWORD_HERE ssh USER@SERVER_IP

    To use a password from a file, use

    echo 'PASSWORD_HERE' > pw_file
chmod 0400 pw_file
sshpass -f pw_file ssh USER@SERVER_IP

    Using password-less authentication using an RSA key is much more secure. But sshpass can be used in places where you can’t use RSA key.

    See SSH

  • Server Setup

    basic server utils
    Cpanel Server Setup

  • basic server utils

    On CentOS/RHEL

    yum update
yum upgrade -y
yum -y remove mlocate
yum install -y nmap lynx wget curl telnet jwhois
yum install -y atop iotop
yum install -y strace
yum install -y git
yum install -y sysstat
yum install -y vim
yum install -y tmux
yum install -y ncurses-devel automake autoconf gcc gmake patch make
yum install -y libcpp libgcc libstdc++ gcc4 gcc4-c++ gcc4-gfortran
yum install -y dos2unix libtool gcc-c++ gcc-c++ compat-gcc-32 compat-gcc-32-c++

    For non cpanel server, install epel

    See Server Setup