Reset root password on CentOS 6 machine

If you have forgotten root user password on your CentOS 6 machine, you can reset the password to new value, without knowing the old one, by booting the machine to single user mode, and resetting the password with passwd command.

Boot to single user mode

During the CentOS boot process, you will be presented with a countdown before CentOS boot process actually begins to load the OS.

Press any key to enter the GNU GRUB menu.

CentOS 6 boot countdown
CentOS boot countdown

On the GNU GRUB menu highlight the kernel you want to boot, and press ‘e’ key to edit the kernel commands before booting.

CentOS 6 kernel select
CentOS 6 kernel select

Once you have entered the kernel edit mode, find the line beginning with kernel, and highlight it, and press ‘e’ key to edit it.

Edit kernel line
Edit kernel line

On the end of the line add the word ‘single’, with white space before ‘single’, and press ENTER to accept the change.

Add single to then end of the kernel line
Add single to then end of the kernel line

Boot the machine with the edited kernel argument, and you will be logged in as root in single user mode.

Now just issue passwd command, and enter the new password two times, when asked.

Change password with passwd command
Change password with passwd command

Once you have changed the password, reboot the machine, and log to it with your new root password.

How to reset root password on Debian 8 (Jessie)

If you have forgotten your root user password for your Debian system, you can reset the password to new value, without entering the old one, by going into grub and editing the commands before booting the system.

Edit GRUB before Debian boot

During you machine boot process, you should be presented with GNU GRUB screen with countdown, before the default boot option is activated.

Press any key during the countdown period stop the boot process, and then press e key to edit the commands before booting.

Debian 8 boot menu
Debian 8 boot menu

One you have entered into editing mode, find the line starting with linux, followed by /boot/vmlinuz-*, and containing section with root=UUID=.

Line should be towards the end, usually two lines before the final line.

On the end of that line, in most case after ro quiet, add one of the following two: init=/bin/bash or init=/bin/sh, as shown on picture below.

Edit kernel line
Edit kernel line

After you have added the init value, press Ctrl+x or F10 key to boot the with the selected options.

Debian should now boot to single user mode, with the root filesystem mounted in read-only mode.

You need to remount it to read-write mode with the following command:
mount -n -o remount,rw /.

After that you can use passwd command to change the root password to a new value.

Change root password with passwd
Change root password with passwd

Type passwd to be asked for a new password, and then reenter the new password again, once asked to retype it, and you should then be presented with following message:

passwd: password updated successfully

You can now reboot your machine, and use the new root password on your system.

Alternative method

If this method is not working for your, you can try to boot the system from a LiveCD, and then mount the partition holding your /etc, and edit the shadow file.

In the shadow file, find the line starting with root:, and change the hashed password between “root:” and next “:” to just “!”.

Shadow file should initially look something like this:

root:random_characters_of_hashed_password:12345::12345:1:::bin:*:12345:0:12345:1:::

After the change it should look something like this:

root:!:12345::12345:1:::bin:*:12345:0:12345:1:::

This allows you to get access to the system with no root password, when you access recovery mode in Advanced options for Debian GNU/Linux.

Press any key during the countdown period stop the boot process, and then select Advanced options for Debian GNU/Linux.

Select Advanced options in menu
Select Advanced options in menu

After you selected Advanced options, select to boot recovery mode.

Select recovery mode in menu
Select recovery mode in menu

After you press Enter to boot recovery mode, you will be logged as root, and can just issue passwd command to change your root password.

Debian 8 recovery mode
Debian 8 recovery mode

 

How to install pdo_pgsql on cPanel server

When you try to install PHP Pecl module PDO_PGSQL, through WHM by going to Home »Software »Module Installers, you might be presented with the following error:

compilation terminated.
make: *** [pdo_pgsql.lo] Error 1
ERROR: `make' failed
The PDO_PGSQL.so object is not in /usr/local/lib/php/extensions/no-debug-non-zts-20131226
Tidying /usr/local/cpanel/3rdparty/php/56/etc/php.ini...
No changes
Tidying /usr/local/lib/php.ini...
 Skipping duplicate extension: pdo_pgsql.so
Wrote changes

You might also get a similar error when trying to install pdo_pgsql through shell with pecl install pdo_pgsql.

creating libtool
appending configuration tag "CXX" to libtool
configure: creating ./config.status
config.status: creating config.h
running: make
/bin/sh /root/tmp/pear/pear-build-roottXvx5k/PDO_PGSQL-1.0.2/libtool --mode=compile cc -I  -I. -I/root/tmp/pear/PDO_PGSQL -DPHP_ATOM_INC -I/root/tmp/pear/pear-build-roottXvx5k/PDO_PGSQL-1.0.2/include -I/root/tmp/pear/pear-build-roottXvx5k/PDO_PGSQL-1.0.2/main
-I/root/tmp/pear/PDO_PGSQL -I/usr/local/include/php -I/usr/local/include/php/main -I/usr/local/include/php/TSRM -I/usr/local/include/php/Zend -I/usr/local/include/php/ext -I/usr/local/include/php/ext/date/lib  -DHAVE_CONFIG_H  -g -O2   -c /root/tmp/pear/PDO_PGSQL/pdo_pgsql.c -o pdo_pgsql.lo
mkdir .libs
 cc -I -I. -I/root/tmp/pear/PDO_PGSQL -DPHP_ATOM_INC -I/root/tmp/pear/pear-build-roottXvx5k/PDO_PGSQL-1.0.2/include -I/root/tmp/pear/pear-build-roottXvx5k/PDO_PGSQL-1.0.2/main -I/root/tmp/pear/PDO_PGSQL -I/usr/local/include/php -I/usr/local/include/php/main -I/usr/local/include/php/TSRM -I/usr/local/include/php/Zend -I/usr/local/include/php/ext -I/usr/local/include/php/ext/date/lib -DHAVE_CONFIG_H -g -O2 -c /root/tmp/pear/PDO_PGSQL/pdo_pgsql.c  -fPIC -DPIC -o .libs/pdo_pgsql.o
/root/tmp/pear/PDO_PGSQL/pdo_pgsql.c:22:20: fatal error: config.h: No such file or directory
 #include "config.h"
                    ^
compilation terminated.
make: *** [pdo_pgsql.lo] Error 1
ERROR: `make' failed

You can install pdo_pgsql by downloading and compiling it manually using following set of commands:

wget http://pecl.php.net/get/PDO_PGSQL-1.0.2.tgz
tar -xzf PDO_PGSQL-1.0.2.tgz
cd PDO_PGSQL-1.0.2/
phpize
./configure
make && make install
echo "extension=pdo_pgsql.so" >> /usr/local/lib/php.ini
Reference:

https://forums.cpanel.net/threads/unable-to-install-pdo_pgsql.554271/

How to clear disk space on cPanel server

By default drives will come with 5% of all filesystems allocated as reserved disk space allocated for privileged users, and not shown as available space.

Since drives in use today tend to be large, reserved block percentage can be lowered to 1%, or specified to specific number of block.

To set the reserved space to 2500 blocks “tune2fs -r 2500” can be used.

tune2fs -r 2500 /dev/sda5

To set reserved space to 1% of disk size “tune2fs -m 1” can be used.

tune2fs -m 1 /dev/sda5

Files that can be cleared by main partitions/folders, to reduce disk usage on cPanel servers:

Reduce /home usage

Several files and folders can be truncated or removed on /home.

When EasyApache is run, it will leave file behind, that were used for Apache/PHP build, that can be removed if space is needed.

EasyApache files can be removed with following command.

rm -rfv /home/cpeasyapache

cPanel FileManager can leave temporary files, that were created during user uploads.
These can be removed with following command:

rm -fv /home/*/tmp/Cpanel_*

If you were moving any accounts to the server with WHM Transfer Tool, temporary account migration files can be left on drive.

These can be removed with following command:

rm -rvf /home*/cpanelpkgrestore.TMP*

Disk space can be recovered by deleting Softaculous and Fantastico backups from user folders, if they are used.

rm -fv /home*/*/.softaculous/backups/*
rm -rfv /home/*/fantastico_backups

If you were making cpmove file manually, they will by default be created inside /home.
You can clean any leftover cpmove files with following command:

rm -rvf /home/cpmove-*

Often large portions of disk space can be used up by large error_log files inside account home folders.

You can empty all error_log files to 0 bytes usage with following command:

find /home/ -name error_log -type f -print -exec truncate --size 0 "{}" \;

If users have large number of account backups in their home folders, those can use up a lot of space.

Accounts backups can be removed from user folders with following command:

for user in `/bin/ls -A /var/cpanel/users` ; do rm -fv /home/$user/backup-*$user.tar.gz ; done
Summary of all used commands, for clearing /home
#Emtpy all error logs
find /home/ -name error_log -type f -print -exec truncate --size 0 "{}" \;
#Remove EasyApache files
rm -rfv /home/cpeasyapache
#Remove Softaculous backups
rm -fv /home*/*/.softaculous/backups/*
#Remove account backups
for user in `/bin/ls -A /var/cpanel/users` ; do rm -fv /home/$user/backup-*$user.tar.gz ; done
#Remove Fantastico backups
rm -rfv /home/*/fantastico_backups
#Remove temporary cPanel files
rm -fv /home/*/tmp/Cpanel_*
#Remove any cpmove files
rm -rvf /home/cpmove-*
#Remove temporary account migration files
rm -rvf /home*/cpanelpkgrestore.TMP*
Reduce /var usage

Disk space in /var can be cleared by deleting archived logs, which will usually end with .gz, or contain year inside their name, like such as “maillog-20161113”.

Archived logs can be cleared with following commands:

rm -fv /var/log/*.gz
rm -fv /var/log/*201*

Disk space in /var can get also get used up by core dump files inside /var/spool/abrt/ directory, which get created in cases of kernel panic.

These file can be cleared up with following command:

rm rfv /var/spool/abrt/*

Check the size of exim stats database, which can sometimes take several gigabytes in size, depending on settings:

du -sh /var/lib/mysql/eximstats/

In case eximstats database is large, consider emptying the database, and changing retention settings.

How to clear or disable eximstats on cPanel

Reduce /usr usage

Disk space in /usr can be cleared by removing cPanel and Apache archived logs, or old installation files of Apache, and if installed, maldet.

Every time you rebuild Apache with EasyApache, old installation files will be moved to “apache.backup*” directory.

Remove old Apache files with following command:

rm -rfv /usr/local/apache.backup*

Similar thing happens with maldet, if it is installed, on updates, old installation will be moved to “maldet.bk*” folder.

Remove old maldet files with following command:

rm -rfv /usr/local/maldet.bk*

Clear disk space by removing archived cPanel logs:

rm -fv /usr/local/cpanel/logs/archive/*.gz

Remove archived Apache logs:

rm -fv /usr/local/apache/logs/*.gz
rm -fv /usr/local/apache/logs/archive/*.gz

Although not often, sometimes maldet logs can use up a lot of space.
Remove maldet logs:

rm -fv /usr/local/maldetect/logs/*
Summary of all used commands, for clearing /usr
#Remove old Apache files
rm -rfv /usr/local/apache.backup*
#Remove old maldet files
rm -rfv /usr/local/maldet.bk*
#Remove maldet logs
rm -fv /usr/local/maldetect/logs/*
#Remove archived cPanel logs
rm -fv /usr/local/cpanel/logs/archive/*.gz
#Remove archived Apache logs
rm -fv /usr/local/apache/logs/*.gz
rm -fv /usr/local/apache/logs/archive/*.gz
References:

How to Free Up Disk Space on a cPanel Server

11 Ways to Free Up Disk Space on a cPanel Server

How to clear or disable eximstats on cPanel

What is eximstats

Eximstats, on WHM/cPanel servers, is used to maintain statistics and information about email messages processed by Exim mail service.

If the data in it is not cleared often enough it can grow, and cause issues with disk space, or MySQL resource usage, as the size of the database can cause higher memory and disk consumption.

Disabling eximstats

If you do not have any need for Exim statistics, which are used for Mail Delivery Reports on  Home »Email »Mail Delivery Reports, gathering exim statistics can be disabled from WHM or command line.

In WHM it can be disabled by going to Home »Service Configuration »Service Manager, and unchecking the service, and then clicking on the Save button on the bottom.

This will stop the database from being populated with new data.

Eximstats in Service Manager
Service Manager

From command line, you can disable the database from being populated by running a following command:
/usr/local/cpanel/bin/tailwatchd --disable=Cpanel::TailWatch::Eximstats

Lowering Eximstats retention time

Database is periodically cleaned, and by default Exim stats are retained in database for 10 days, which can be changed in WHM by going to Home »Server Configuration »Tweak Settings and changing the “The interval, in days, to retain Exim stats in the database” setting on the “Stats and Logs” tab.

Setting can also be changed by altering the “exim_retention_days” value in “/var/cpanel/cpanel.config” file.

Empty eximstats database

Database can be cleared either by deleting from its four tables, defers, failures, sends and smtp, or by dropping the database completely, and creating a fresh one with empty tables from “/usr/local/cpanel/etc/eximstats_db.sql” file.

To delete all of the data from the tables following command can be used:

mysql -e "use eximstats;delete from defers;delete from failures;delete from sends;delete from smtp;delete from smtp;"

To drop the database and recreate it again, following commands can be used:

mysqladmin drop eximstats
mysqladmin create eximstats
mysql eximstats < /usr/local/cpanel/etc/eximstats_db.sql
References:

https://forums.cpanel.net/threads/problem-in-eximstats.363382/

https://confluence2.cpanel.net/display/ALD/Service+Manager#ServiceManager-tailwatchd(TailWatchDrivers)

https://documentation.cpanel.net/display/ALD/Tweak+Settings+-+Stats+and+Logs#TweakSettings-StatsandLogs-Theinterval,indays,toretainEximstatsinthedatabase