Posts Tagged ‘root’

No space left on device with free disk space / Why no space left on device while there is plenty of disk space on drive – Running out of Inodes

Tuesday, November 17th, 2015



On one of the servers, I'm administrating the websites started showing some Mysql database table corrup errors like:


Table './database_name/site_news_list_com' is marked as crashed and last (automatic?) repair failed

The server is using Oracle MySQL server community stable edition on Debian GNU / Linux 6.0, so I first thought during work the server crashed either due to some bug issue in MySQL or it crashed due to some PHP cron job that did something messy. Thus to solve the crashed tables, tried using mysqlcheck tool which helped pretty fine, at many times whether there were database / table corruptions. I've run the following set of mysqlcheck commands with root (superuser) in a bash shell after logging in through SSH:


server:~# /usr/bin/mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–check –all-databases -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log
server:~# /usr/bin/mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf –analyze –all-databases -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log
server:~# /usr/bin/mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–auto-repair –optimize –all-databases -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log
server:~# /usr/bin/mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–optimize –all-databases -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log

In order for above commands to work, I've created the /root/.my.cnf containing my root (mysql CLI) mysql username and password, e.g. file has content like below:




Btw a good note here is its generally a good idea (if you want to have consistent mysql databases) to automatically execute via a cron job 2 times a month, I've in root cronjob the following:


crontab -u root -l |grep -i mysqlcheck
04 06 5,10,15,20,25,1 * * /usr/bin/mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–check –all-databases –silent -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log 07 06 5,10,15,20,25,1 * * /usr/bin/mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf –analyze –all-databases –silent -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log 12 06 5,10,15,20,25,1 * * /usr/bin/mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–auto-repair –optimize –all-databases –silent -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log 17 06 5,10,15,20,25,1 * * /usr/bin/mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–optimize –all-databases –silent -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log

Strangely I got a lot of errors that some .MYI / .MYD .frm temp files, necessery for the mysql tables recovery can't be written inside /home/mysql/database_name

That was pretty weird and I thought there might be some issues with permissions, causing the inability to write, due to some bug or something so I went straight and checked /home/mysql/database_name permissions, e.g.::


server:/home/mysql/database_name# ls -ld soccerfame
drwx—— 2 mysql mysql 36864 Nov 17 12:00 soccerfame
server:/home/mysql/database_name# ls -al1|head -n 10
total 1979012
drwx—— 2 mysql mysql 36864 Nov 17 12:00 .
drwx—— 36 mysql mysql 4096 Nov 17 11:12 ..
-rw-rw—- 1 mysql mysql 8712 Nov 17 10:26 1_campaigns_diez.frm
-rw-rw—- 1 mysql mysql 14672 Jul 8 18:57 1_campaigns_diez.MYD
-rw-rw—- 1 mysql mysql 1024 Nov 17 11:38 1_campaigns_diez.MYI
-rw-rw—- 1 mysql mysql 8938 Nov 17 10:26 1_campaigns.frm
-rw-rw—- 1 mysql mysql 8738 Nov 17 10:26 1_campaigns_logs.frm
-rw-rw—- 1 mysql mysql 883404 Nov 16 22:01 1_campaigns_logs.MYD
-rw-rw—- 1 mysql mysql 330752 Nov 17 11:38 1_campaigns_logs.MYI

As seen from above output, all was perfect with permissions, so it should have been something else, so I decided to try to create a random file with touch command inside /home/mysql/database_name directory:


touch /home/mysql/database_name/somefile-to-test-writtability.txt touch: cannot touch ‘/scr1/data/somefile-to-test-writtability.txt‘: No space left on device

Then logically I thought the /home/mysql/ mounted ext4 partition got filled, because of crashed SQL database or a bug thus, checked with disk free command df whether there is enough space on server:

server:~# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md1 20G 7.6G 11G 42% /
udev 10M 0 10M 0% /dev
tmpfs 13G 1.3G 12G 10% /run
tmpfs 32G 0 32G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 32G 0 32G 0% /sys/fs/cgroup
/dev/md2 256G 134G 110G 55% /home

Well that's weird? Obviously only 55% of available disk space is used and available 134G which was more than enough so I got totally puzzled why, files can't be written.

Then very logically, I thought it might be that /home directory has remounted as read only, because the SSD memory disk on server is failing and checked for errors in dmesg, i.e.:


server:~# dmesg|grep -i error

Also checked how exactly was partition mounted, to check whether it is (RO) read-only:


server:~# mount -l|grep -i /home
/dev/md2 on /home type ext4 (rw,relatime,discard,data=ordered)

Now everything become even more weirder, as obviously the disk continued to be claiming no space left on device, while in reality there was plenty of disk space.

Then after running a quick research on the internet for the no space left on device with free disk space, I've come across this great thread which let me realize the partition run out of inodes and that's why no new file inodes could be assigned and therefore, the linux kernel is refusing to write the file on ext4 partition.

For those who haven't heard of Linux Partition Inodes here is link to Wikipedia and a quick quote:


In a Unix-style file system, the inode is a data structure used to represent a filesystem object, which can be one of various things including a file or a directory. Each inode stores the attributes and disk block location(s) of the filesystem object's data.[1] Filesystem object attributes may include manipulation metadata (e.g. change,[2] access, modify time), as well as owner and permission data (e.g. group-id, user-id, permissions).[3]
Directories are lists of names assigned to inodes. The directory contains an entry for itself, its parent, and each of its children.

Once I understood it is the inodes, I checked how many of them are occupied with cmd:


server:~# df -i /home
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/md2 17006592 17006592 0 100% /home

You see, there were 0 (zero) free file inodes on server and that was the reason for no space left on device while there was actually free disk space

To clean up (free) some inodes on partition, first thing I did is to delete all old logs which were inside /home and files I positively know not to be necessery, then to find which directories allocating most innodes used:


server:~# find . -xdev -type f | cut -d "/" -f 2 | sort | uniq -c | sort -n

If you're on a regular old fashined IDE Hard Drive and not SSD or you have too much files inside this command will take really long …:

Therefore a better solution might be to frist:

a) Try to find root folders with large inodes count:

for i in /home/*; do echo $i; find $i |wc -l; done
Try to find specific folders:

You should get output like:



b) Then once you know the directory allocating most inodes, run the command again to see the sub-directories with most files (eating) partition innodes:


for i in /home/webservice/*; do echo $i; find $i |wc -l; done


One usual large folder which could free you some nodes is the linux source headers, but in my case it was simply a lot of tiny old logs being logged on the system for few years in the past without cleaning:

After deleting the log dirs and cache folder in my case /home/new_website/{log,cache}:

server:~# rm -rf /home/new_website/log/*
server:~# rm -rf /home/new_website/cache/*



a) Then, stopping Apache webserver to check prevent Apache to use MySQl databases while running database repair and restaring MySQL:

server:~# /etc/init.d/apache2 stop Restarting MySQL server
server:~# /etc/init.d/mysql restart

b) And re-issuing MySQL Check / Repair / Optimize database commands:


mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–check –all-databases -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log

mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf –analyze –all-databases -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log

mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–auto-repair –optimize –all-databases -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log

mysqlcheck –defaults-extra-file=/etc/mysql/debian.cnf \–optimize –all-databases -u root -p`grep -i password /root/.my.cnf |sed -e 's#password=##g'`>> /var/log/cronwork.log

c) And finally starting the Apache Webserver again:

server:~# /etc/init.d/apache2 start

Some innodse got freed up:

server:~# df -i /home Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/md2 17006592 16797196 209396 99% /home

And hooray by God's Grace and with help of prayers of The most Holy Theotokos (Virgin) Mary, websites started again !

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Adding another level of security to your shared Debian Linux webhosting server with SuPHP

Tuesday, April 7th, 2015


There are plenty of security schemes and strategies you can implement if you're a Shared Web Hosting company sysadmin however probably the most vital one is to install on Apache + PHP Webserver SuPHP module.

# apt-cache show suphp-common|grep -i descrip -A 4

Description: Common files for mod suphp Suphp consists of an Apache module (mod_suphp for either Apache 1.3.x or Apache 2.x) and a setuid root binary (suphp) that is called by the Apache module to change the uid of the process executing the PHP interpreter to the owner of the php script.

So what SuPHP actuall  does is to run separate CPanel / Kloxo etc. Users with separate username and groupid permissions coinciding with the user present in /etc/passwd , /etc/shadow files existing users, thus in case if someone hacks some of the many customer sites he would be able to only write files and directories under the user with which the security breach occured.

On servers where SuPHP is not installed, all  systemusers are using the same UserID / GuID to run PHP executable scripts under separate domains Virtualhost which are coinciding with Apache (on Debian / Ubuntu  uid, gid – www-data) or on (CentOS / RHEL / Fedora etc. – user apache) so once one site is defaced  exploited by a worm all or most server websites might end up infected with a Web Virus / Worm which will be trying to exploit even more sites of a type running silently in the background.  This is very common scenarios as currently there are donezs of PHP / CSS / Javasripts / XSS vulnerability exploited on VPS and Shared hosting servers due to failure of a customer to update his own CMS  scripts / Website  (Joomla, Wordpress, Drupal etc.) and the lack of resource to regularly monitor all customer activities / websites.

Therefore installing SuPHP Apache module is essential one to install on new serverslarge hosting providers as it saves the admin a lot of headache from spreading malware across all hosted servers sites ..
Some VPS admins that are security freaks tend to also install SuPHP module together with many chrooted Apache / LiteSpeed / Nginx webservers each of which running in a separate Jailed environment.

Of course using SuPHP besides giving a improved security layer to the webserver has its downsides such as increased load for the server and making Apache PHP scripts being interpretted a little bit slower than with plain Apache + PHP but performance difference while running a site on top of SuPHP is often not so drastic so you can live it up ..

Installing SuPHP on a Debian / Ubuntu servers is a piece of cake, just run the as root superuser, usual:

# apt-get install libapache2-mod-suphp

Once installed only thing to make is to turn off default installed Apache PHP module (without SuPHP compiled support and restart Apache webserver):

# a2dismod php5 …

# /etc/init.d/apache2 restart

To test the SuPHP is properly working on the Apache Webserver go into some of many hosted server websites DocumentRoot

And create new file called test_suphp.php with below content:

# vim test_suphp.php

Then open in browser http://whatever-website/test_suphp.php assuming that system(); function is not disabled for security reasons in php.ini you should get an User ID, GroupID bigger than reserved system IDs on GNU / Linux e.g. ID > UID / GID 99

Its also a good idea to take a look into SuPHP configuration file /etc/suphp/suphp.conf and tailor options according to your liking 

If different hosted client users home directories are into /home directory, set in suphp.conf

;Path all scripts have to be in


Also usually it is a good idea to set 


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Check your Server Download / Upload Internet Speed from Console on Linux / BSD / Unix howto

Tuesday, March 17th, 2015

If you've been given a new dedicated server from a New Dedicated-Server-Provider or VPS with Linux and you were told that a certain download speed to the Server is guaranteed from the server provider, in order to be sure the server's connection to the Internet told by service provider is correct it is useful to run a simple measurement console test after logging in remotely to the server via SSH.

Testing connection from Terminal is useful because as you probably know most of Linux / UNIX servers doesn't have a GUI interface and thus it is not possible to test Internet Up / Down Bandwidth through

1. Testing Download Internet Speed given by ISP / Dedi-Server Provider from Linux Console

For the download speed (internet) test the historical approach was to just try downloading the Linux kernel source code from with some text browser such as lynx or links count the seconds for which the download is completed and then multiple the kernel source archive size on the seconds to get an approximate bandwidth per second, however as nowdays internet connection speeds are much higher, thus it is better to try to download some Linux distribution iso file, you can still use kernel tar archive but it completed too fast to give you some good (adequate) statistics on Download bandwidth.

If its a fresh installed Linux server probably you will probably not have links / elinks and lynx text internet browers  installed so install them depending on deb / rpm distro with:

If on Deb Linuz distro:


root@pcfreak:/root# apt-get install –yes links elinks lynx


On RPM Based Linuz distro:


[root@fedora ~]# yum install -y lynx elinks links


Conduct Internet  Download Speed with links
root@pcfreak:/root# links


(Note that the kernel link is current latest stable Kernel source code archive in future that might change, so try with latest archive.)

You can also use non-interactive tool such as wget curl or lftp to measure internet download speed

To test Download Internet Speed with wget without saving anything to disk set output to go to /dev/null 


root@pcfreak:~# wget -O /dev/null



You see the Download speed is 104 Mbit/s this is so because I'm conducting the download from my local 100Mbit network.

For the test you can use my mirrored version of Hirens BootCD

2. Testing Uplink Internet speed provided by ISP / Server Provider from Linux (SSH) Console

To test your uplink speed you will need lftp or iperf command tool.


root@pcfreak:~# apt-cache show lftp|grep -i descr -A 12
Description: Sophisticated command-line FTP/HTTP client programs
 Lftp is a file retrieving tool that supports FTP, HTTP, FISH, SFTP, HTTPS
 and FTPS protocols under both IPv4 and IPv6. Lftp has an amazing set of
 features, while preserving its interface as simple and easy as possible.
 The main two advantages over other ftp clients are reliability and ability
 to perform tasks in background. It will reconnect and reget the file being
 transferred if the connection broke. You can start a transfer in background
 and continue browsing on the ftp site. It does this all in one process. When
 you have started background jobs and feel you are done, you can just exit
 lftp and it automatically moves to nohup mode and completes the transfers.
 It has also such nice features as reput and mirror. It can also download a
 file as soon as possible by using several connections at the same time.


root@pcfreak:/root# apt-cache show iperf|grep -i desc -A 2
Description: Internet Protocol bandwidth measuring tool
 Iperf is a modern alternative for measuring TCP and UDP bandwidth performance,
 allowing the tuning of various parameters and characteristics.


To test Upload Speed to Internet connect remotely and upload any FTP file:


root@pcfreak:/root# lftp -u hipo -e 'put; bye'



On Debian Linux to install iperf:


root@pcfreak:/root# apt-get install –yes iperf


On latest CentOS 7 and Fedora (and other RPM based) Linux, you will need to add RPMForge repository and install with yum


[root@centos ~]# rpm -ivh  rpmforge-release-0.5.3-1.el7.rf.x86_64.rpm

[root@centos ~]# yum -y install iperf


Once having iperf on the server the easiest way currently to test it is to use speedtest server –  located at the Serverius datacenters, AS50673 and is running on a 10GE connection with 5GB cap.


root@pcfreak:/root# iperf -c -P 10
Client connecting to, TCP port 5001
TCP window size: 16.0 KByte (default)
[ 12] local port 54258 connected with port 5001
[  7] local port 54252 connected with port 5001
[  5] local port 54253 connected with port 5001
[  9] local port 54251 connected with port 5001
[  3] local port 54249 connected with port 5001
[  4] local port 54250 connected with port 5001
[ 10] local port 54254 connected with port 5001
[ 11] local port 54255 connected with port 5001
[  6] local port 54256 connected with port 5001
[  8] local port 54257 connected with port 5001
[ ID] Interval       Transfer     Bandwidth
[  9]  0.0-10.2 sec  4.05 MBytes  3.33 Mbits/sec
[ 10]  0.0-10.2 sec  3.39 MBytes  2.78 Mbits/sec
[ 11]  0.0-10.3 sec  3.75 MBytes  3.06 Mbits/sec
[  4]  0.0-10.3 sec  3.43 MBytes  2.78 Mbits/sec
[ 12]  0.0-10.3 sec  3.92 MBytes  3.18 Mbits/sec
[  3]  0.0-10.4 sec  4.45 MBytes  3.58 Mbits/sec
[  5]  0.0-10.5 sec  4.06 MBytes  3.24 Mbits/sec
[  6]  0.0-10.5 sec  4.30 MBytes  3.42 Mbits/sec
[  8]  0.0-10.8 sec  3.92 MBytes  3.03 Mbits/sec
[  7]  0.0-10.9 sec  4.03 MBytes  3.11 Mbits/sec
[SUM]  0.0-10.9 sec  39.3 MBytes  30.3 Mbits/sec


You see currently my home machine has an Uplink of 30.3 Mbit/s per second, that's pretty nice since I've ordered a 100Mbits from my ISP (Unguaranteed Bandwidth Connection Speed) and as you might know it is a standard practice for many Internet Proviers to give Uplink speed of 1/4 from the ISP provided overall bandwidth 1/4 would be 25Mbi/s, meaning my ISP (Bergon.NET) is doing pretty well providing me with even more than promised (ordered) bandwidth.

Iperf is probably the choice of most sysadmins who have to do regular bandwidth in local networks speed between 2 servers or test  Internet Bandwidth speed on heterogenous network with Linux / BSDs / AIX / HP-UX (UNIXes). On HP-UX and AIX and other UNIXes for which iperf doesn't have port you have to compile it yourself.

If you don't have root /admin permissions on server and there is python language enterpreter installed you can use script to test internet throughput connectivity
speedtest_cli uses to test server up / down link just in case if script is lost in future I've made ownload mirror of is here

Quickest way to test net speed with


$ lynx -dump >
$ chmod +x


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How to find and Delete Duplicate files in directory on Linux server with find and fdupes command

Monday, March 16th, 2015


Linux / UNIX find command is very helpful to do a lot of tasks to us admins such as Deleting empty directories to free up occupied inodes or finding and printing only empty files within a root file system within all sub-directories
There is too much of uses of find, however one that is probably rarely used known by sysadmins find command use is how to search for duplicate files on a Linux server:

find -not -empty -type f -printf “%s\n” | sort -rn | uniq -d | xargs -I{} -n1 find -type f -size {}c -print0 | xargs -0 md5sum | sort | uniq -w32 –all-repeated=separate

If you're curious how does duplicate files finding works, they are found by comparing file sizes and MD5 signatures, followed by a byte-by-byte comparison.

Most common application of below command is when you want to search and get rid of some old obsolete files which you forgot to delete such as old /etc/ configurations, old SQL backups and PHP / Java / Python programming code files etc.

If you have to do a regular duplicate file find on multiple servers Linux servers perhaps you should install and use  fdupes command.
On Debian Linux to install it:

root@pcfreak:/# apt-cache show fdupes|grep -i descr -A 4
Description: identifies duplicate files within given directories
 FDupes uses md5sums and then a byte by byte comparison to find
 duplicate files within a set of directories. It has several useful
 options including recursion.
Homepage: apt-get install –yes fdupes

To search for duplicate files with fdupes in lets /etc/ just run fdupes without arguments:


root@pcfreak:/# fdupes /etc/



If you want to look up for all duplicate files within root directory:

root@pcfreak:/# fdupes -r /etc/
Building file list /


You can also find duplicate files for multiple directories by just passing all directories as arguments to fdupes


root@pcfreak:/# fdupes -r /etc/ /usr/ /root /disk /nfs_mount /nas

The -r argument (makes a recursive subdirectory search for duplicates), if you want to also see what is the size of duplicate files found add -S option


fdupes -r -S /etc/ /usr/ /root /disk /nfs_mount /nas


If you want to delete all duplicate files within lets say /etc/


root@pcfreak:/# fdupes -d /etc/

fdupes is also available and installable also on RPM based Linux distros Fedora / RHEL / CentOS etc., install on CentOS with:

[root@centos~ ]# yum -y install fdupes

There is also a port available for those who want to run it on FreeBSD on BSD install it from ports:


freebsd# cd /usr/ports/sysutils/fdupes
freebsd# make install clean

If you have a GUI environment installed on the server and you don't want to bother with command line to search for all duplicate files under main filesystem and other lint (junk) files take a look at FSlint


If you're looking for a GUI cross platform duplicate file finder tool that runs on all major used Operating Systems Mac OS X / Windows / Linux take a look at dupeGuru


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How to check Apache Webserver and MySQL server uptime – Check uptime of a running daemon with PS (process) command

Tuesday, March 10th, 2015


Something very useful that most Apache LAMP (Linux Apache MySQL PHP) admins should know is how to check Apache Webserver uptime and MySQL server running (uptime).
Checking Apache / MySQL uptime is primary useful for scripting purposes – creating auto Apache / MySQL service restart scripts, or just as a quick console way to check what is the status and uptime of Webserver / SQL.

My experience as a sysadmin shows that lack of Periodic Apache and MySQL restart every week or every month often creates sys-admin a lot of a headaches cause (Apache / NGINX / SQL  server) starts eating too much memory or under some circumstances leads to service or system crashes. Periodic system main services restart is especially helpful in case if Website's backend programming code is writetn in a bad and buggy uneffient way by unprofessional (novice) programmers.
While I was still working as Senior SysAdmin in Design.BG, I've encountered many such Crappy Web applications developed by dozen of different programmers (because company's programmers changed too frequently and many of the hired Web Developers ,were still learning to program, I guess same is true also for other Start-UP Web / IT Company where crappy programming code is developed you will certainly need to keep an eye on Apache / MYSQL uptime.  If that's the case below 2 quick one liners with PS command will help you keep an eye on Apache / MYSQL uptime


ps -eo "%U %c %t"| grep apache2 | grep -v grep|grep root
root     apache2            02:30:05

Note that above example is Debian specific on RPM based distributions you will have to grep for httpd instead of apache2

ps -eo "%U %c %t"| grep http| grep -v grep|grep root

root     apache2            10:30:05

To check MySQL uptine:

ps -eo "%U %c %t"| grep mysqld
root     mysqld_safe        20:42:53
mysql    mysqld             20:42:53

Though example is for mysql and Apache you can easily use ps cmd in same way to check any other Linux service uptime such as Java / Qmail / PostgreSQL / Postfix etc.

ps -eo "%U %c %t"|grep qmail
qmails   qmail-send      19-01:10:48
qmaill   multilog        19-01:10:48
qmaill   multilog        19-01:10:48
qmaill   multilog        19-01:10:48
root     qmail-lspawn    19-01:10:48
qmailr   qmail-rspawn    19-01:10:48
qmailq   qmail-clean     19-01:10:48
qmails   qmail-todo      19-01:10:48
qmailq   qmail-clean     19-01:10:48
qmaill   multilog        40-18:02:53


 ps -eo "%U %c %t"|grep -i nginx|grep -v root|uniq
nobody   nginx           55-01:22:44


ps -eo "%U %c %t"|grep -i java|grep -v root |uniq
hipo   java            27-22:02:07


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How much memory users uses in GNU / Linux and FreeBSD – Commands and Scripts to find user memory usage on Linux

Tuesday, February 17th, 2015




If you have to administrate a heterogenous network with Linux and FreeBSD or other UNIX like OSes you should sooner or later need for scripting purposes to have a way to list how much memory separate users take up on your system. Listing memory usage per user is very helpful for admins who manager free-shells or for companies where you have developers, developing software directly on the server via ssh. Being able to check which process eats up most memory is essential for every UNIX / Linux sysadmin, because often we as admins setup (daemons) on servers and we forgot about their existence, just to remember they exist 2 years later and see the server is crashing because of memory exhaustion. Tracking server bottlenecks where RAM memory and Swapping is the bottleneck is among the main swiss amry knives of admins. Checking which user occupies all server memory is among the routine tasks we're forced to do as admins, but because nowdays servers have a lot of memory and we put on servers often much more memory than ever will be used many admins forget to routinely track users / daemons memory consumption or even many probably doesn't know how.  Probably all are aware of the easiest wy to get list of all users memory in console non interactively with free command, e.g.:

free -m
             total       used       free     shared    buffers     cached
Mem:         32236      26226       6010          0        983       8430
-/+ buffers/cache:      16812      15424
Swap:        62959        234      62725


but unfortunately free command only shows overall situation with memory and doesn't divide memory usage by user

Thus probably to track memory users the only known way for most pepole is to (interactively) use good old top command or if you like modern (colorful) visualization with htop:

debian:~# top



Once top runs interactive press 'm' to get ordered list of processes which occupy most system memory on Linux server.Top process use status statistics will refresh by default every '3.0' seconds to change that behavior to '1' second press  s and type '1.0'. To get Sort by Memory Use in htop also press 'm'

[root@mail-server ~]# htop



However if you need to be involved in scripting and setting as a cron job tasks to be performed in case if high memroy consumption by a service you will need to use few lines of code. Below are few examples on how Linux user memory usage can be shown with ps cmd.

Probably the most universal way to see memory usage by users on Debian / Ubuntu / CentOS / RHEL and BSDs (FreeBSD / NetBSD) is with below one liner:


server:~# ps hax -o rss,user | awk '{a[$2]+=$1;}END{for(i in a)print i” “int(a[i]/1024+0.5);}' | sort -rnk2
daemon 0
debian-tor 63
dnscache 1
dnslog 0
hipo 21
messagebus 1
mysql 268
ntp 2
privoxy 1
proftpd 1
qmaill 0
qmailq 0
qmailr 0
qmails 0
qscand 291
root 94
shellinabox 1
snmp 1
statd 1
vpopmail 80
www-data 6765


Output is in MBs

Below is output from machine where this blog is running, the system runs ( Apache + PHP + MySQL Webserver + Qmail Mail server and Tor) on Debian GNU / Linux.

 To get more human readable (but obscure to type – useful for scripting) output list of which user takes how much memory use on deb / rpm etc. based Linux :


server:~# echo "USER                 RSS      PROCS" ; echo "——————– ——– —–" ; \
ps hax -o rss,user | awk '{rss[$2]+=$1;procs[$2]+=1;}END{for(user in rss) printf “%-20s %8.0f %5.0f\n”, user, rss[user]/1024, procs[user];}' | sort -rnk2


USER                 RSS      PROCS
——————– ——– —–
www-data                 6918   100
qscand                    291     2
mysql                     273     1
root                       95   120
vpopmail                   81     4
debian-tor                 63     1
hipo                       21    15
ntp                         2     1
statd                       1     1
snmp                        1     1
shellinabox                 1     2
proftpd                     1     1
privoxy                     1     1
messagebus                  1     1
dnscache                    1     1
qmails                      0     2
qmailr                      0     1
qmailq                      0     2
qmaill                      0     4
dnslog                      0     1
daemon                      0     2


It is possible to get the list of memory usage listed in percentage proportion, with a tiny for bash loop and some awk + process list command

TOTAL=$(free | awk '/Mem:/ { print $2 }')
for USER in $(ps haux | awk '{print $1}' | sort -u)
    ps hux -U $USER | awk -v user=$USER -v total=$TOTAL '{ sum += $6 } END { printf "%s %.2f\n", user, sum / total * 100; }'

107 1.34
115 2.10
119 1.34
daemon 1.32
dnscache 1.34
dnslog 1.32
hipo 1.59
mysql 4.79
ntp 1.34
privoxy 1.33
proftpd 1.32
qmaill 1.33
qmailq 1.33
qmailr 1.32
qmails 1.33
qscand 4.98
root 1.33
snmp 1.33
statd 1.33
vpopmail 2.35
www-data 86.48

Also a raw script which can be easily extended to give you some custom information on memory use by user is here.
You can also want to debug further how much memory a certain users (lets say user mysql and my username hipo) is allocating, this can easily be achieved ps like so:

root@pcfreak:~# ps -o size,pid,user,command -u mysql –sort -size
796924 14857 mysql   /usr/sbin/mysqld –basedir=/usr –datadir=/var/lib/mysql –plugin-dir=/usr/lib/mysql/plugin –user=mysql –pid-file=/var/run/mysqld/ –socket=/var/run/mysqld/mysqld.sock –port=3306


root@pcfreak~# ps -o size,pid,user,command -u hipo –sort -size|less
13408 19063 hipo     irssi
 3168 19020 hipo     SCREEN
 2940  2490 hipo     -bash
 1844 19021 hipo     /bin/bash
 1844 19028 hipo     /bin/bash
 1844 19035 hipo     /bin/bash
 1844 19042 hipo     /bin/bash
 1844 19491 hipo     /bin/bash
 1844 22952 hipo     /bin/bash
  744  2487 hipo     sshd: hipo@pts/0
  744  2516 hipo     sshd: hipo@notty
  524  2519 hipo     screen -r
  412  2518 hipo     /usr/lib/openssh/sftp-server

You see from below output user running with www-data (this is Apache Webserver user in Debian) is eating 86.48% of overall system memory and MySQL server user is using only 4.79% of available memory

Output is shown in Megabytes per username memory usage, and user memory usage is ordered (stepping-down / descentive) from top to bottom

Getting more thoroughful and easier to read reporting without beeing a 31337 bash coder you can install and use on Linux smem – memory reporting tool .

SMEM can provide you with following memory info:

  • system overview listing
  • listings by process, mapping, user
  • filtering by process, mapping, or user
  • configurable columns from multiple data sources
  • configurable output units and percentages
  • configurable headers and totals
  • reading live data from /proc
  • reading data snapshots from directory mirrors or compressed tarballs
  • lightweight capture tool for embedded systems
  • built-in chart generation

Installing smem on Debian 6 / 7 / Ubuntu 14.04 / Turnkey Linux etc. servers is done with standard:


debian:~# apt-get install –yes smem



To install smem on CentOS 6 / 7:


[root@centos ~ ]# yum -y install smem

On Slackware and other Linux-es where smem is not available as a package you can install it easily from binary archive with:


cd /tmp/
tar xvf smem-1.3.tar.gz
sudo cp /tmp/smem-1.3/smem /usr/local/bin/
sudo chmod +x /usr/local/bin/smem


Two most common smem uses are:


root@mail:~# smem -u
User     Count     Swap      USS      PSS      RSS
dnslog       1       44       48       54      148
qmaill       4      232      124      145      464
hipo        11    13552     8596     9171    13160
qscand       2     4500   295336   295602   297508
root       188   217312  4521080  4568699  7712776


Below command shows (-u – Report memory usage by user, -t – show totals, -k – show unix suffixes)

root@mail:~# smem -u -t -k
User     Count     Swap      USS      PSS      RSS
dnslog       1    44.0K    48.0K    54.0K   148.0K
qmaill       4   232.0K   124.0K   145.0K   464.0K
hipo        11    13.2M     8.4M     9.0M    12.9M
qscand       2     4.4M   288.4M   288.7M   290.5M
root       188   212.2M     4.3G     4.4G     7.4G
           206   230.1M     4.6G     4.6G     7.7G

To get users memory use by percentage with smem:

root@mail:~# smem -u -p
User     Count     Swap      USS      PSS      RSS
dnslog       1    0.00%    0.00%    0.00%    0.00%
qmaill       4    0.00%    0.00%    0.00%    0.01%
hipo        11    0.17%    0.11%    0.11%    0.16%
qscand       2    0.05%    3.63%    3.63%    3.66%
root       194    2.64%   56.18%   56.77%   95.56%

It is also useful sometimes when you want to debug system overloads caused by external hardware drivers loaded into kernel causing issues to get list of system wide memory use sorted by user


 root@mail:~# smem -w -p
Area                           Used      Cache   Noncache
firmware/hardware             0.00%      0.00%      0.00%
kernel image                  0.00%      0.00%      0.00%
kernel dynamic memory        38.30%     36.01%      2.28%
userspace memory             60.50%      0.98%     59.53%
free memory                   1.20%      1.20%      0.00%

smem is very nice as if you're running it on a Desktop Linux system with Xserver installed you can see also graphical output of memory use by application:

root@desktop-pc:~# smem –bar pid -c "pss uss"


smem can even generate graphical pie charts to visualize better memory use

root@desktop-pc:~# smem -P '^k' –pie=name



If there is a high percentage shown in firmware/hardware this means some buggy module is loaded in kernel eating up memory, to fix it debug further and remove the problematic module.
userspace memory actually shows the percantage of memory out of all server available RAM that is being consumed by applications (non kernel and other system processes which make the system move). You see in above example the kernel itself is consuming about 40% of system overall available memory. 

We all know the SWAP field stands for hard disk drive used as a memory when system is out, but there are 3 fields which smem will report which will be probably unclear for most here is also explanation on what USS / PSS / RSS means?

RSS is the Resident Set Size and is used to show how much memory is allocated to that process and is in RAM. It does not include memory that is swapped out. It does include memory from shared libraries as long as the pages from those libraries are actually in memory. It does include all stack and heap memory too.

There is also PSS (proportional set size). This is a newer measure which tracks the shared memory as a proportion used by the current process. So if there were two processes using the same shared library from before.

USS stands for Unique set size, USS is just the unshared page count, i.e. memory returned when process is killed 

PSS = Proportional set size, (PSS),  is a more meaningful representation of the amount of memory used by libraries and applications in a virtual memory system.  
Because large portions of physical memory are typically shared among multiple applications, the standard measure of memory usage known as resident set size (RSS) will significantly overestimate memory usage. The parameter PSS instead measures each application’s “fair share” of each shared area to give a realistic measure. For most admins checking out the output from RSS (output) should be enough, it will indicate which user and therefore which daemon is eating up all your memory and will help you to catch problematic services which are cause your server to run out of RAM and start swapping to disk.

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Venice Italy – An Ancient Church city and San Marco’s and saint Lucia Holy Relics – Travel impressions from Venezia

Thursday, October 9th, 2014


I’m on a honeymoon with my wife Svetlana in Italy our first stop from our 16 days trip through out Venice, a root governing region of the Holy Roman Catholic empire. We’re staying in CA Fortuny hotel, which I warmly recommend to anyone willing to visit Venice (Venezia). We had a flight to Vienna and from Vienna we took another flight to Venice. My first impressions from Italy was the Venice airport which is simple and the snacks and coffee from the coffee machines were on affordable price. As we flight from another EU country member of the Schengen zone, there was no need to do any passport check so we just had to wait 15 minutes and pick up the luggage from bag platform. Once there we looked forward for the information which is located nearby a Change Buro. We were told to go to the nearby ticket office where we learned, to travel to Venezia we had a few options, one was to travel by bus to Venice and walk by 30 minutes to the hotel costing only 6 euro per person and the other was to travel by boat transportation but this was exceesively expensive 15 euro per person!!!. The lady on the tickets office in Airport tried selling us a tickets each 15 euro automatically in responce to my question to give us tickets for transport to San Marco square / Piazza San Marco, good that my wife asked about an alternative transportation and we knew about the cheaper bus. The bus is pretty straight forward to find it is right infront of airport exit. The bus led is directly to Venice, as we didn’t know how to go to San Marco square, we answered a kind Italian who explained us in fluent English. Another lady nearby in the bus heard, where we wanted to go and told us we’re in her direction so we can follow her. As it was raining heavily, she said whe might pick up the Vaporetto (a transportation boats used through out all Venice like a bus :). We had a small chat with the kind lady Gabriela, who explained us she is an English teacher and she is coming back from England for a weeks study exchange seminars and she knows well CA Fortuny hotel which is a 10 room Romantic hotel in the heart of Venice. As we walked by about 30 minutes we talked about various stuff ranging from life in Venice, English study, the current state of education in Venice, the state of Christianity nowadays etc. Once being in the Hotel, we were warmly received by the porter a young man probably age 20-25. I was schoked by the door-man piercing which was scary looking like a just hammered nail in the center of a spider crawling. I asked the portier what is this and he answered this is a micro-dermal implant or something alike. I’ve noticed that people living in western europe have started to get crazy on tatoos and piercings. It seems it is exceptionally modern among youngster people in western europe to Tattoo their right hands or do piercings on various places. It seems less and less people know what does the Holy Hible says about Tattoos and piercings?, I quote literally from the scriptures on tatoos and piercings
Leviticus 19:28 Ye shall not make any cuttings in your flesh for the dead, nor print any marks upon you: I am the Lord.King James Version Bible (KJV). There is also even an old testamental holy bible instruction against the so popular nowadays skinning of head hair (the so called) skin-head movement.

Leviticus 21:55 They shall not make baldness upon their head, neither shall they shave off the corner of their beard, nor make any cuttings in their flesh.King James Bible Version (KJV). Actually for me it is no strange that so many western people tatoo, their right hand as in the advertisements and throughout our daily lives there are hidden messages trying to convince us to accept the 666 future mark of the beast that will appear in the times when the enemy of Christ the antichrist appears publicly and tries to deceive everyone to accept his 666 mark on the right hand. From the saints and holy fathers we Christians know that this 666 mark will stand up for his name …



In Venice we had truly a great time, we were close to the city center so logically we went to see the most important place in Venice St. Marc’s Square, the square is called like this because it is infront of a Basicila (Roman Catholic Cathedral Church), which is keeping the holy relics of Saint Evangelist Apostle Marc who wrote the New Testament Gospel of Mark.

The Holy relics of St. Apostle Mark are kept in a stone sarcophagus in the Church alter. It is interesting fact that holy relics were stolen from Alexandria with help of two greek monks to save them from muslim desacration and destruction.

Because the whole city is “living on a water” in venice there is no public transportation (no land bus, land taxi etc.), all transportation is on water. There is water bus / taxi – Vaparetto
, there are boat-markets selling fruits and vegetables, water-police, water-ambulance and even water catafalque


People interested in history and particularly Christianity will definitely enjoy venice as the whole city is full with Roman Catholic Churches in various types of architectures some medieval some from the 11-th century and some started even in more ancient times. Orthodox Christians would be happy to know there is even a Russian orthodox Church in Venice San Zan Degola (In English Saint John the Baptist).

By God’s merce we had the chance to venerate the holy relics of Santa Lucia / Saint Lucy of Syracuse (year 283 – 304) whose incorruptable body is kept in a Catholic Church.


The saint body is preserved incorruptable for amazingly 1710 years!!! This is a clear proof of a saintship and truthfulness of Christian faith as well is a real miracle before your eyes one can see !!


As Venice is an ancient city it is a great site for Christian Orthodox pilgrimage for Russian speking people a very good Russian resource listing most of the Venice related holy relics is here .
Near San Marco Piazza it is worthy to enter Doge’s palace which is currently a museum exposing a great a lot of Venice culture and history. Doge’s palace was the supreme authority of Republic palace, to make an analogue it used to like Kremlin in Russia nowadays.

A ticket for Doge’s palace costed 16 euro per person and ticket allows you to visit another 3 museums in Venice.

Venice has 177 canals on 177 small islands as there is no public transport and venice is small most of the time we walked in order to save money for Vaperatto (whose ticket costs 6 euro). There are no bus station in Venice but there is a train station (Santa Lucia railway station). Current Venice population is around 270 000 ppl.


As a notable tourist destination unfortunately everything in Venice is quite expensive. Even simple things as ice cream costs 3-4 euro per ice-ball, to have a restaurant dinner usually you will have to spend at least 30 / 40 euro per person. There are also some cheaper Trattorias – a type of less formal restaurant with casual service and less shiny looking but usually with cheaper food. You can eat in Tratoria a full 3 course meal for as cheap as 12 to 15 euro per person. Also in Tratoria you can experience more of an Italian type of restaurant, as the personal there usually doesn’t speak English and most of people to eat there are Italians.

We were in Venice only for one full day in Venice and thus we eat only once in a restaurant type of place recommended by a local the Taverna San Trovaso . A 2 persons meals plus 2 cups of wine there costed us cheap for Venice about 30 euro.

The building architecture in Venice is truly unique and you can see piece of art and beauty on literally any corner of it. The shops are all around the city and every kind of souvenir is quite expensive, though you can usually try to bargain to buy a souvenir for half the price 🙂
A notable traditional souvenirs to buy is beautiful colorful glas souvenirs and ofcourse the famous ball masks



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Allowing MySQL users access from all hosts – Fixing mysql ERROR 1045 (28000): Access denied for user ‘root’@’’ (using password: YES)

Friday, June 20th, 2014


I recently migrated MySQL database server from host A to host B (, because I wanted to have the mysql database server on a separate machine (have separation of server running services and have a dedicated mysql server).

MySQL server host (running on localhost previously was set from my mysql config my.cnf to listen and serve connections on localhost with

bind-address =

). MySQL is used by a Tomcat running Java application on localhost and my task was to set the Tomcat to use the MySQL database remotely to MySQL host B (new remote hostname where MySQL is moved is and is running on IP

Migration from MySQL Db server 1 (host A) to MySQL Db server 2 (host B) is done by binary copying the mysql database directory which in this case is (as it is a Debian server installed MySQL), the standard directory where mysql stores its database data is /var/lib/mysql ( datadir = /var/lib/mysql in /etc/mysql/my.cnf)

Binary copying of data from MySQL db (host A) to MySQL Db (host B) is done with rsync

After migrating and trying to login on migrated mysql  database on with mysql cli client:

remotesysadmin:~$ mysql -u root -p

I got following error:

ERROR 1045 (28000): Access denied for user 'root'@'' (using password: YES)

To fix the issue I had to login remotely from old migration server mysql (host A) cli:

mysql:~$ mysql -u root -p -h

and  run SQL commands:

GRANT USAGE ON *.* TO 'root'@'' IDENTIFIED BY 'secret-mysql-pass';

Query OK, 0 rows affected (0.03 sec)
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)

Another way to solve the problem is to add the root user to be able to connect from any host (Enable MySQL root access from all host), to do so issue:


Note: In newer version of MySQL, flush privileges could be omitted.

Another approach if you want to substitute access from localhost for all users and enable all users to be able to authenticate to mysql remotely is to execute SQL Query:

UPDATE USER SET host='%' WHERE host='localhost';

Allowing all users to be able to connect from anywhere on the internet is a very bad security practice anyways, if you already have a tight firewall setup and you can only access the server via specific remote IP addresses allowing MySQL access from all hosts / ips should be ok.

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Linux: how to show all users crontab – List all cronjobs

Thursday, May 22nd, 2014

I'm doing another server services decomissioning and part of decomissioning plan is: Removing application and all related scripts from related machines (FTP, RSYNC, …). In project documentation I found a list with Cron enabled shell scripts:

#Cron tab excerpt:
1,11,21,31,41,51 * * * */webservices/tools/scripts/

that has to be deleted, however there was nowhere mentioned under what kind of credentials (with what kind of user) are the cron scripts running? Hence I had to look up all users that has cronjobs and find inside each user's cronjobs whether respective script is set to run. Herein I will explain shortly how I did that.

Cronjobs by default has few locations from where cronjobs are setupped depending on their run time schedule. First place I checked for the scripts is

/etc/crontabs # cat /etc/crontabs SHELL=/bin/sh
# check scripts in cron.hourly, cron.daily, cron.weekly, and cron.monthly
-*/15 * * * * root test -x /usr/lib/cron/run-crons && /usr/lib/cron/run-crons >/dev/null 2>&1
59 * * * * root rm -f /var/spool/cron/lastrun/cron.hourly
14 4 * * * root rm -f /var/spool/cron/lastrun/cron.daily
29 4 * * 6 root rm -f /var/spool/cron/lastrun/cron.weekly
44 4 1 * * root rm -f /var/spool/cron/lastrun/cron.monthly

I was not really user via what user is shell script run, therefore I looked first if someone doesn't set the script to run via crontab's standard locations for Daily, Hourly,Weekly and Monthly cronjobs:

a) Daily set cron jobs are in:


b) Hourly set cron jobs:


c) Weekly cron jobs are in:


d) Monthly cron jobs:


There is also a location read by crontab for all Software (package distribution) specific cronjobs – all run under root user privileges.:

e) Software specific script cron jobs are in:

As the system has about 327 users in /etc/passwd, checking each user's cronjob manually with:

# crontab -u UserName -l

was too much time consuming thus it is a good practice to list


directory and to see which users has cron jobs defined


# ls -al /var/spool/cron/*
-rw——- 1 root root 11 2007-07-09 17:08 /var/spool/cron/deny

total 0
drwxr-xr-x 2 root root 80 2014-05-22 11:15 .
drwx—— 4 root root 120 2008-02-25 15:45 ..
-rw-r–r– 1 root root 0 2014-05-22 04:15 cron.daily

total 8
drwx—— 2 root root 72 2014-04-03 03:43 .
drwx—— 4 root root 120 2008-02-25 15:45 ..
-rw——- 1 root root 4901 2014-04-03 03:43 root

/var/spool/cron – is crond (/usr/bin/cron/)'s spool directory.

# ls -al /var/spool/cron/tabs/ total 8
drwx------ 2 root root 72 2014-04-03 03:43 .
drwx------ 4 root root 120 2008-02-25 15:45 ..
-rw------- 1 root root 4901 2014-04-03 03:43 root

Above output shows only root superuser has defined crons.

Alternative way to check all user crontabs is via quick Linux one liner shell script show all user cron jobs

for i in $(cat /etc/passwd | sed -e "s#:# #g" | awk '{ print $1 }'); do
echo "user $i --- crontab ---";
crontab -u $i -l 2>&1 >/dev/null;
echo '----------';

Note that above short script has to run with root user. Enjoy 🙂

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MySQL: How to check user privileges and allowed hosts to connect with mysql cli

Wednesday, April 2nd, 2014


On a project there are some issues with root admin user unable to access the server from remote host and the most probable reason was there is no access to the server from that host thus it was necessary check mysql root user privilegse and allowed hosts to connect, here SQL query to do it:

mysql> select * from `user` where  user like 'root%';
| Host                           | User | Password                                  | Select_priv | Insert_priv | Update_priv | Delete_priv | Create_priv | Drop_priv | Reload_priv | Shutdown_priv | Process_priv | File_priv | Grant_priv | References_priv | Index_priv | Alter_priv | Show_db_priv | Super_priv | Create_tmp_table_priv | Lock_tables_priv | Execute_priv | Repl_slave_priv | Repl_client_priv | Create_view_priv | Show_view_priv | Create_routine_priv | Alter_routine_priv | Create_user_priv | Event_priv | Trigger_priv | ssl_type | ssl_cipher | x509_issuer | x509_subject | max_questions | max_updates | max_connections | max_user_connections |
| localhost                      | root | *5A07790DCF43AC89820F93CAF7B03DE3F43A10D9 | Y           | Y           | Y           | Y           | Y           | Y         | Y           | Y             | Y            | Y         | Y          | Y               | Y          | Y          | Y            | Y          | Y                     | Y                | Y            | Y               | Y                | Y                | Y              | Y                   | Y                  | Y                | Y          | Y            |          |            |             |              |             0 |           0 |               0 |                    0 |
| server737                        | root | *5A07790DCF43AC89820F93CAF7B03DE3F43A10D9 | Y           | Y           | Y           | Y           | Y           | Y         | Y           | Y             | Y            | Y         | Y          | Y               | Y          | Y          | Y            | Y          | Y                     | Y                | Y            | Y               | Y                | Y                | Y              | Y                   | Y                  | Y                | Y          | Y            |          |            |             |              |             0 |           0 |               0 |                    0 |
|                      | root | *5A07790DCF43AC89820F93CAF7B03DE3F43A10D9 | Y           | Y           | Y           | Y           | Y           | Y         | Y           | Y             | Y            | Y         | Y          | Y               | Y          | Y          | Y            | Y          | Y                     | Y                | Y            | Y               | Y                | Y                | Y              | Y                   | Y                  | Y                | Y          | Y            |          |            |             |              |             0 |           0 |               0 |                    0 |
| | root | *5A07790DCF43FC89820A93CAF7B03DE3F43A10D9 | Y           | Y           | Y           | Y           | Y           | Y         | Y           | Y             | Y            | Y         | Y          | Y               | Y          | Y          | Y            | Y          | Y                     | Y                | Y            | Y               | Y                | Y                | Y              | Y                   | Y                  | Y                | Y          | Y            |          |            |             |              |             0 |           0 |               0 |                    0 |
| server4586                        | root | *5A07790DCF43AC89820F93CAF7B03DE3F43A10D9 | N           | N           | N           | N           | N           | N         | N           | N             | N            | N         | N          | N               | N          | N          | N            | N          | N                     | N                | N            | N               | N                | N                | N              | N                   | N                  | N                | N          | N            |          |            |             |              |             0 |           0 |               0 |                    0 |
|              | root | *5A07790DCF43AC89820F93CAF7B03DE3F43A10D9 | N           | N           | N           | N           | N           | N         | N           | N             | N            | N         | N          | N               | N          | N          | N            | N          | N                     | N                | N            | N               | N                | N                | N              | N                   | N                  | N                | N          | N            |          |            |             |              |             0 |           0 |               0 |                    0 |
6 rows in set (0.00 sec)

mysql> exit

Here is query explained:

select * from `user` where  user like 'root%'; query means:

select * – show all
from `user` – from user database
where user like 'root%' – where there is match in user column to any string starting with 'root*',

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