Category: Linux

cat

Joining files with Cat on Linux

July 24, 2020

Joining files with Cat on Linux

I have a movie cut with hjspit.

-rw-r--r-- 1 root root 110100480 Apr 17 10:42 MSFT_1.avi.001
-rw-r--r-- 1 root root 110100480 Apr 17 10:45 MSFT_1.avi.002
-rw-r--r-- 1 root root 110100480 Apr 17 10:45 MSFT_1.avi.003
-rw-r--r-- 1 root root 110100480 Apr 17 10:47 MSFT_1.avi.004
-rw-r--r-- 1 root root 110100480 Apr 17 10:47 MSFT_1.avi.005
-rw-r--r-- 1 root root 110100480 Apr 17 10:49 MSFT_1.avi.006
-rw-r--r-- 1 root root 110100480 Apr 17 10:49 MSFT_1.avi.007
-rw-r--r-- 1 root root 110100480 Apr 17 10:51 MSFT_1.avi.008
-rw-r--r-- 1 root root  62759034 Apr 17 10:51 MSFT_1.avi.009

To join them on Linux, run

cat MSFT_1.avi.00? > MSFT_1.avi

Back to cat

July 24, 2020

Linux alias

alias can be used to create custom commands. To see all alias on your computer, you can run command

alias

Here are some of the avlias defined on my computer

alias ipy='/home/boby/venv/bin/ipython'
alias ok='ssh [email protected] -p 3333'
alias venv='source ~/venv/bin/activate'

First alias allow me to type ipy instead of typing the actual command /home/boby/venv/bin/ipython, which is larger and difficult to type.

Second command allow to to ssh to a server just by typing “ok” in command prompt.

To add alias, you need to edit

vi ~/.bashrc

and add alias commands you need in the file. Here is what i have on a server

root@ok:~# cat .bashrc
# ~/.bashrc: executed by bash(1) for non-login shells.

# Note: PS1 and umask are already set in /etc/profile. You should not
# need this unless you want different defaults for root.
# PS1='${debian_chroot:+($debian_chroot)}\h:\w\$ '
# umask 022

# You may uncomment the following lines if you want `ls' to be colorized:
# export LS_OPTIONS='--color=auto'
# eval "`dircolors`"
# alias ls='ls $LS_OPTIONS'
# alias ll='ls $LS_OPTIONS -l'
# alias l='ls $LS_OPTIONS -lA'
#
# Some more alias to avoid making mistakes:
# alias rm='rm -i'
# alias cp='cp -i'
# alias mv='mv -i'
alias ll='ls -la --color'
alias rm='rm -i'
alias grep='grep --color=auto'
export HISTTIMEFORMAT="%d/%m/%y %T "


alias sra-fcloud='ssh [email protected]'

root@ok:~#

July 24, 2020

Install bind in CentOS 7

bind is a DNS server. To install bind on CentOS 7, run

yum install bind bind-utils -y

Enable bind to start on boot

systemctl enable named

Start bind

systemctl start named

You can see status with

systemctl status named

Setup firewall

You need to allow DNS ports UDP/TCP 53 in firewall. On CentOS 7, you can run

firewall-cmd --zone=public --permanent --add-service=dns
firewall-cmd --reload

Configure bind

By default bind only listens to local IP, to make it accessable from outside, you need to edit named.conf

vi /etc/named.conf

Find

        listen-on port 53 { 127.0.0.1; };
        listen-on-v6 port 53 { ::1; };

Comment out those two lines by adding # at start of the lines.

        #listen-on port 53 { 127.0.0.1; };
        #listen-on-v6 port 53 { ::1; };

We need our DNS server access query from anyone on internet. For this, find

        allow-query     { localhost; };

Replace with

        allow-query     { any; };

Since we only want our DNS server resolve domains hosted on our server, disable recursion.

Find

        recursion yes;

Replace with

        recursion no;

Now restart bind with

systemctl restart bind

Adding Domain to bind

To server a domain, you need to add the domain to bind. For this edit file

vi /etc/named.conf

at end of the file, add

zone "DOMAIN.EXTN" IN {
   type master;
   file "/var/named/DOMAIN.EXTN.zone";
   allow-update { none; };
};

Now create zone file

vi /var/named/DOMAIN.EXTN.zone

Add following

$TTL            86400
@                 IN SOA            DOMAIN.EXT.  admin.DOMAIN.EXT. (
100     ; serial
1H      ; refresh
1M      ; retry
1W      ; expiry
1D )    ; minimum
@                   IN NS             ns1.DOMAIN.EXT.
@                   IN A                 YOUR_IP_ADDR_HERE
ns1                 IN A                 YOUR_IP_ADDR_HERE
@                   IN MX   10      mail.DOMAIN.EXT.
mail                IN A                 YOUR_IP_ADDR_HERE
www                 IN A                 YOUR_IP_ADDR_HERE

Restart bind

vi /var/named/DOMAIN.EXTN.zone

You can verify domain is resolving with command

nslookup DOMAIN.EXT SERVER_IP_HERE

See bind

July 24, 2020

SSH Port Forwarding
On a remote server, we have an application running on 127.0.0.1:8010. Since the application is listening on internal IP address 127.0.0.1, we can’t access it remotely. To access this application, we can use SSH port forwarding.
```
ssh -L 8010:127.0.0.1:8010 [email protected] -p 3333
```
In above example, application running on server lab.serverok.in is available on my local computer at
```
http://127.0.0.1:8010
```
July 23, 2020

kex_exchange_identification: read: Connection reset by peer

When connecting to Ubuntu 20.04 server using SSH from a Mac computer, get an error

kex_exchange_identification: read: Connection reset by peer

On checking the servers log file (/var/log/auth.log), found the following error message

Jul 23 06:53:34 server sshd[24147]: Unable to negotiate with 17.19.44.24 port 47280: no matching key exchange method found. Their offer: diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1 [preauth]

To fix this, on the server, edit sshd_config

vi /etc/ssh/sshd_config

At end of the file, add

KexAlgorithms +diffie-hellman-group1-sha1

Restart ssh

systemctl restart ssh

See SSH

July 23, 2020

Cpanel CloudLinux set all users to use alt-php
If your cpanel server have cloudlinux + PHP Selector installed, you need to set all site to use inherit PHP before you can use PHP Selector.

This can be done in MultiPHP Manager or using command line
```
for i in $(cut -d: -f1 /etc/userdatadomains );do whmapi1 php_set_vhost_versions version=inherit vhost-0=$i;done
```
Tis command will set all web sites to use inherit PHP.

To set all site to use alt-PHP 7.4, run
```
selectorctl --change-to-version=7.4 --version=native
```
This will change PHP version for all sites that use native PHP to alt-PHP 7.4

Or you can use
```
cd /var/cpanel/users
ls -1 | awk '{ print "selectorctl --set-user-current=7.4 --user="$1 }' | sh
```
See cloudlinux
July 20, 2020

Ant Media Server

Ant Media Server is a media streaming server with WebRTC support.

https://antmedia.io
Install Ant Media Server on CentOS 8
Ant Media Server Ubuntu firewall configuration
Steaming to Anti Media Server using ffmpeg

Open Source versiong of Ant Media Server can be downloaded from

https://github.com/ant-media/Ant-Media-Server

Install Anti Media Server on Ubuntu 18.04

At the time of writing this post, latest version of Ant Media Server is ant-media-server-2.0.0-community-2.0.0-20200504_1842.zip, replace it with latest version available on github.

cd /usr/local/src
wget https://github.com/ant-media/Ant-Media-Server/releases/download/ams-v2.0.0/ant-media-server-2.0.0-community-2.0.0-20200504_1842.zip
wget https://raw.githubusercontent.com/ant-media/Scripts/master/install_ant-media-server.sh 
chmod 755 install_ant-media-server.sh
./install_ant-media-server.sh ant-media-server-2.0.0-community-2.0.0-20200504_1842.zip

After installation, you will see Ant Meida Server listens on following ports

[root@Ant-Media-Server ~]# netstat -lntp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 127.0.0.1:5599          0.0.0.0:*               LISTEN      1594/jsvc.exec      
tcp        0      0 0.0.0.0:34501           0.0.0.0:*               LISTEN      1594/jsvc.exec      
tcp        0      0 0.0.0.0:1935            0.0.0.0:*               LISTEN      1594/jsvc.exec      
tcp        0      0 0.0.0.0:5080            0.0.0.0:*               LISTEN      1594/jsvc.exec      
[root@Ant-Media-Server ~]#

To access Ant Media Server, go to

http://your-server-ip:5080

When visiting first time, you will be asked to create a new user.

Ant Media Server

Installing SSL

To install SSL, you need to point a domain or sub domain to server IP, then run following commands

cd /usr/local/antmedia
./enable_ssl.sh -d YOUR_DOMAIN_HERE

After installation, you will be able to access site using HTTPS on following URL

https://YOUR_DOMAIN_HERE:5443

Test Video Streaming Applictaion available at

https://YOUR_DOMAIN_HERE::5443/WebRTCApp/

Manage Anti Media Server

To start/stop/restart Ant Media Server, use

systemctl start antmedia
systemctl stop antmedia
systemctl restart antmedia

Firewall

Anti Media Server use following ports

tcp:1935 - RTMP
tcp:5080 - HTTP
tcp:5443 - HTTPS
tcp:5554 - RTSP
udp:5000-65000 - WebRTC & RTSP

July 20, 2020

Bash if statement

Check if first augment to script is –help

if [ "$1" = "--help" ]; then
    echo "$0 --help = shows help"
    exit 0
fi

Check if a file exists and is executable

if [ -f "/usr/bin/curl" ]; then
    echo "curl exists"
fi

Check if a binary file exists and is executable

if [ -x "/usr/bin/curl" ]; then
    echo "curl exists and executable"
fi

Check if previous command was sucessfull or not

if [ "$?" != 0 ]; then
    echo failed
    exit 1
fi

Check if variabe set or not

if [ -z ${USER} ]; then
    echo "\$USER not set"
else
    echo "\$USER =  $USER"
fi

July 19, 2020

Install Python 3.8 on CentOS 6 from source

To install Python 3.8 on CentOS, you need to install OpenSSL as the one installed by CentOS from yum is very old.

cd /usr/local/src
wget https://www.openssl.org/source/openssl-1.1.1g.tar.gz
tar xvf openssl-1.1.1g.tar.gz
cd openssl-1.1.1g
./config --prefix=/usr/serverok/openssl --openssldir=/usr/serverok/openssl no-ssl2
make
make install

Now edit file

vi ~/.bash_profile

at end of the file, add

export PATH=/usr/serverok/openssl/bin:$PATH
export LD_LIBRARY_PATH=/usr/serverok/openssl/lib
export LC_ALL="en_US.UTF-8"
export LDFLAGS="-L/usr/serverok/openssl/lib -Wl,-rpath,/usr/serverok/openssl/lib"

Make the settings active with command

source ~/.bash_profile

Now we can install Python 3.8 with

cd /usr/local/src
wget https://www.python.org/ftp/python/3.8.4/Python-3.8.4.tar.xz
tar xvf Python-3.8.4.tar.xz
cd /usr/local/src/Python-3.8.4
make clean && make distclean
./configure --enable-optimizations  --with-openssl=/usr/serverok/openssl/
make altinstall

Now python 3.8 will be available in your system under /usr/local/bin

root@server12:~# python3.8 --version
Python 3.8.4
root@server12:~# which python3.8
/usr/local/bin/python3.8
root@server12:~#

July 18, 2020

apt-get An error occurred during the signature verification

When running apt update, i get following 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.cloud.google.com cloud-sdk-jessie InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6A030B21BA07F4FB

To fix this error, run

apt-key adv --keyserver keys.gnupg.net --recv-keys 6A030B21BA07F4FB

July 17, 2020

Expired Updates for this repository will not be applied

When running apt update on a Debian jessie server, i get following error

E: Release file for http://archive.debian.org/debian/dists/jessie-backports/InRelease is expired (invalid since 513d 20h 41min 47s). Updates for this repository will not be applied

To fix the error, run

echo "Acquire::Check-Valid-Until false;" | sudo tee -a /etc/apt/apt.conf.d/10-nocheckvalid

July 17, 2020