No space left on device in server | PHPMysql not connect session | Full Inodes 100% | Check CPU Process and MEMORY

Issues

1. open(/var/lib/php/sessions/sess_, O_RDWR) failed: No space left on device (28)
2. PHPMysql not connect
3. Database not connect

Solusions

Check CPU and MEMORY usage of server from terminal

ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%cpu | head

df -h

Check file size

find /home/ -size +100M 

 

 Check INODES in server (Inode mean total files into server)

df -i

Search INODES from system and perticular folder (Get number of file in perticular directory)

for i in /var/www/html/*; do echo $i; find $i |wc -l; done

Check INODES into specific directory

ls -l /var/lib/php/sessions | wc -l

Remove all files from specific directory

rm -r /var/lib/php/sessions/ 

If you are using PHP so you can create code in any existing file

$path = '/var/lib/php/sessions/';
$dir = opendir($path);
$i = 0;
while ($dir && ($file = readdir($dir)) !== false) {
    unlink($path.$file);
    echo $i.' - '.$path.$file.'<br>';
    if($i == 50000){
        exit;
    }
    $i++;
}

Optimized my.cnf MySQL configuration due to hign CPU usage in Ubuntu

# Optimized my.cnf configuration for MySQL/MariaSQL
#
# by Fotis Evangelou, developer of Engintron (engintron.com)
#
# === Updated July 2018 ===
#
# The settings provided below are a starting point for a 2GB - 4GB RAM server with 2-4 CPU cores.
# If you have less or more resources available you should adjust accordingly to save CPU,
# RAM and disk I/O usage.
# The settings marked with a specific comment or the word "UPD" after the value
# should be adjusted for your system by using database diagnostics tools like:
# https://github.com/major/MySQLTuner-perl
# or
# https://launchpad.net/mysql-tuning-primer (supports MySQL up to v5.6)
#
#
# Note that if there is NO comment after a setting value, then 99,9% of the times you won't need to adjust it.
#
#
# THINGS TO DO AFTER YOU UPDATE MY.CNF - TROUBLESHOOTING
# If any terminal commands are mentioned, make sure you execute them as "root" user.
# If MySQL cannot start or restart, then perform the following actions.
#
# 1. If the server had the stock database configuration and you added or updated any
#    "innodb_log_*" settings (as suggested below), then execute these commands ONLY
#    the first time you apply this configuration:
#
#    $ rm -rvf /var/lib/mysql/ib_logfile*
#    $ chown -R mysql:mysql /var/lib/mysql
#    $ service mysql restart
#
#    or use the shorthand command:
#    $ rm -rvf /var/lib/mysql/ib_logfile*; chown -R mysql:mysql /var/lib/mysql; service mysql restart
#
# 2. If the setting "bind-address" is not commented out, then make sure the file /etc/hosts is
#    properly configured. A good example of a "clean" /etc/hosts file is something like this:
#
#    127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
#    ::1       localhost localhost.localdomain localhost6 localhost6.localdomain6
#    1.2.3.4   hostname.domain.tld hostname # Replace accordingly!
#
#    Finally restart the database service:
#
#    $ service mysql restart
#
# 3. If the database service cannot restart even after the first 2 steps, make sure the database data folder
#    (common for either MySQL or MariaDB) "/var/lib/mysql" is owned by the "mysql" user AND group.
#    Additionally, the folder itself can have 0751 or 0755 file permissions. To fix it, simply do this:
#    $ chown -R mysql:mysql /var/lib/mysql
#    $ chmod 0755 /var/lib/mysql
#
#    Finally restart the database service:
#
#    $ service mysql restart
[mysql]
port                            = 3306
socket                          = /var/run/mysqld/mysqld.sock
[mysqld]
# Required Settings
basedir                         = /usr
bind_address                    = 127.0.0.1 # Change to 0.0.0.0 to allow remote servers to connect to this server's
                                            # database instance
datadir                         = /var/lib/mysql
max_allowed_packet              = 256M
max_connect_errors              = 1000000
pid_file                        = /var/run/mysqld/mysqld.pid
port                            = 3306
skip_external_locking
skip_name_resolve
socket                          = /var/run/mysqld/mysqld.sock
#sql_mode                       = ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION,ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES # Enable for b/c with databases
                                                                                                                                               # using null dates
tmpdir                          = /tmp
user                            = mysql
# InnoDB Settings
default_storage_engine          = InnoDB
innodb_buffer_pool_instances    = 1     # Use 1 instance per 1GB of InnoDB pool size
innodb_buffer_pool_size         = 1G    # Use up to 70-80% of RAM & optionally check if /proc/sys/vm/swappiness is set to 0
innodb_file_per_table           = 1
innodb_flush_log_at_trx_commit  = 0
innodb_flush_method             = O_DIRECT
innodb_log_buffer_size          = 16M
innodb_log_file_size            = 128M
#innodb_thread_concurrency      = 4     # Optional: Set to the number of CPUs on your system (minus 1 or 2) to better
                                        # contain CPU usage. E.g. if your system has 8 CPUs, try 6 or 7 and check
                                        # the overall load produced by MySQL/MariaDB.
# MyISAM Settings
query_cache_limit               = 4M    # UPD
query_cache_size                = 48M   # UPD
query_cache_type                = 1
key_buffer_size                 = 48M   # UPD
low_priority_updates            = 1
concurrent_insert               = 2
# Connection Settings
max_connections                 = 100   # UPD
back_log                        = 512
thread_cache_size               = 100
thread_stack                    = 192K
interactive_timeout             = 180
wait_timeout                    = 180
# Buffer Settings
join_buffer_size                = 3M    # UPD
read_buffer_size                = 2M    # UPD
read_rnd_buffer_size            = 4M    # UPD
sort_buffer_size                = 4M    # UPD
# Table Settings
# In systemd managed systems like Ubuntu 16.04 or CentOS 7, you need to perform an extra action for table_open_cache & open_files_limit
# to be overriden (also see comment next to open_files_limit).
# E.g. for MySQL 5.7, please check: https://dev.mysql.com/doc/refman/5.7/en/using-systemd.html
# and for MariaDB check: https://mariadb.com/kb/en/library/systemd/
table_definition_cache          = 8000  # UPD
table_open_cache                = 8000  # UPD
open_files_limit                = 24000 # UPD - This can be 2x to 3x the table_open_cache value or match the system's
                                        # open files limit usually set in /etc/sysctl.conf or /etc/security/limits.conf
                                        # In systemd managed systems this limit must also be set in:
                                        # /etc/systemd/system/mysqld.service.d/override.conf (for MySQL 5.7+) and
                                        # /etc/systemd/system/mariadb.service.d/override.conf (for MariaDB)
max_heap_table_size             = 128M
tmp_table_size                  = 128M
# Search Settings
ft_min_word_len                 = 3     # Minimum length of words to be indexed for search results
# Logging
log_error                       = /var/lib/mysql/mysql_error.log
log_queries_not_using_indexes   = 1
long_query_time                 = 5
slow_query_log                  = 0     # Disabled for production
slow_query_log_file             = /var/lib/mysql/mysql_slow.log
[mysqldump]
# Variable reference
# For MySQL 5.7: https://dev.mysql.com/doc/refman/5.7/en/mysqldump.html
# For MariaDB:   https://mariadb.com/kb/en/library/mysqldump/
quick
quote_names
max_allowed_packet              = 64M

Refer From : https://gist.github.com/fevangelou/fb72f36bbe333e059b66 

Mysql usage grater than 100% of CPU in ubuntu 18.04 | 16.04 in AWS

 You need to update server configuration.

1. Open terminal

2. Put command : sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf

3. Find following variables
key_buffer_size         = 16M
max_allowed_packet      = 16M
thread_stack            = 192K
thread_cache_size       = 8
query_cache_limit      = 1M
query_cache_size        = 16M
Change To
key_buffer_size         = 160M
max_allowed_packet      = 160M
thread_stack            = 1920K
thread_cache_size       = 80
query_cache_limit       = 1024M
query_cache_size        = 2048M

4. Restart mysql : sudo /etc/init.d/mysql restart

5. Restart apache2 sudo systemctl restart apache2

6. Check CPU usage : ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%cpu | head

 For more Information please Refer : https://dev.mysql.com/doc/refman/5.7/en/server-configuration.html