Linux VPS cheat sheet. Linux commands for CentOS/RHEL and Ubuntu/Debian

MannDude · Aug 18, 2013

Figured this thread could be a handy resource for everyone at all skill-levels. Sometimes you just want to copy and paste a command you've used a hundred times (DD-tests, for example) or are just having a brain fart and forgot how to do something. Well... this thread is for you, my friend! Let's get started!

I'm just going to start off with the absolute basics, was planning I'd do several of these and then add more to this post as people respond with additional ones.

By the way, the outputs of the commands I show I've done on my Raspberry Pi running Debian on my local network.

General Commands > The Basics > All Distributions

Uptime Command:

uptime

Shows the uptime of a VPS, output example below:

root@rpi-server:~# uptime
16:11:59 up 12 days, 8:10, 1 user, load average: 0.08, 0.03, 0.05

Free memory Command

free -m

Shows the available free memory on your Linux system. Read here for more: http://www.linuxatemyram.com/

root@rpi-server:~# free -m
             total       used       free     shared    buffers     cached
Mem:           438        379         58          0         49        213
-/+ buffers/cache:        117        321
Swap:            0          0          0

Processes and resources used command:

top

Realtime process and resource usage. You can see your load average, uptime, and processes that are consuming system resources. To exit 'top', just hit 'Q'. You can CTRL + M to sort the processes according to their memory usage from highest to lowest, which can come in handy in figuring out what is using up your RAM. (Thanks [member=wcypierre] for that tip)

root@rpi-server:~# top

top - 16:16:59 up 12 days, 8:15, 1 user, load average: 0.00, 0.01, 0.05
Tasks: 65 total,   1 running, 64 sleeping,   0 stopped,   0 zombie
%Cpu(s): 0.7 us, 0.7 sy, 0.0 ni, 98.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem:    448776 total,   389568 used,    59208 free,    50916 buffers
KiB Swap:        0 total,        0 used,        0 free,   218484 cached

PID USER      PR NI VIRT RES SHR S %CPU %MEM    TIME+ COMMAND
17744 root      20   0 3112 1304 924 R   1.0 0.3   0:00.27 top
2081 mysql     20   0 294m 47m 5320 S   0.3 10.8 75:16.16 mysqld
    1 root      20   0 2100 676 576 S   0.0 0.2   0:37.37 init
    2 root      20   0     0    0    0 S   0.0 0.0   0:00.10 kthreadd
    3 root      20   0     0    0    0 S   0.0 0.0   0:07.65 ksoftirqd/0
    4 root      20   0     0    0    0 S   0.0 0.0   0:00.01 kworker/0:0
    5 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 kworker/0:0H
    6 root      20   0     0    0    0 S   0.0 0.0   2:02.08 kworker/u:0
    7 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 kworker/u:0H
    8 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 khelper
    9 root      20   0     0    0    0 S   0.0 0.0   0:00.00 kdevtmpfs
   10 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 netns
   12 root      20   0     0    0    0 S   0.0 0.0   0:00.25 bdi-default
   13 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 kblockd
   14 root      20   0     0    0    0 S   0.0 0.0   0:00.22 khubd
   15 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 rpciod
   16 root      20   0     0    0    0 S   0.0 0.0   0:00.66 khungtaskd
   17 root      20   0     0    0    0 S   0.0 0.0   0:08.23 kswapd0
   18 root      20   0     0    0    0 S   0.0 0.0   0:00.00 fsnotify_mark
   19 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 nfsiod
   20 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 crypto
   27 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 kthrotld
   28 root       1 -19     0    0    0 S   0.0 0.0   0:00.00 VCHIQ-0
   29 root       1 -19     0    0    0 S   0.0 0.0   0:00.00 VCHIQr-0
   30 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 VCHIQs-0
   31 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 iscsi_eh
   32 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 dwc_otg
   33 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 DWC Notificatio
   35 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 deferwq
   36 root      20   0     0    0    0 S   0.0 0.0   0:00.00 kworker/u:2
   37 root      20   0     0    0    0 S   0.0 0.0   6:29.95 mmcqd/0
   38 root       0 -20     0    0    0 S   0.0 0.0   0:04.70 kworker/0:1H
   39 root      20   0     0    0    0 S   0.0 0.0   0:22.44 jbd2/mmcblk0p2-
   40 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 ext4-dio-unwrit
153 root      20   0 2744 980 608 S   0.0 0.2   0:00.32 udevd
235 root       0 -20     0    0    0 S   0.0 0.0   0:00.00 bcm2708_spi.0
1371 root      20   0 4852 2280 568 S   0.0 0.5   0:00.23 dhclient
1574 root      20   0 28060 1576 1064 S   0.0 0.4   0:03.93 rsyslogd
1609 root      20   0 2248 844 672 S   0.0 0.2   0:05.02 cron
1717 root      20   0 1712 556 460 S   0.0 0.1   0:00.13 mysqld_safe
1899 root      20   0 6168 1040 620 S   0.0 0.2   0:00.12 sshd
2082 root      20   0 1804 608 532 S   0.0 0.1   0:00.01 logger
2174 root      20   0 2200 708 588 S   0.0 0.2   0:00.01 getty
2175 root      20   0 2200 708 588 S   0.0 0.2   0:00.01 getty
2176 root      20   0 2200 708 588 S   0.0 0.2   0:00.01 getty
2177 root      20   0 2200 708 588 S   0.0 0.2   0:00.01 getty
2178 root      20   0 2200 708 588 S   0.0 0.2   0:00.01 getty
2179 root      20   0 2200 708 588 S   0.0 0.2   0:00.01 getty
2804 root      20   0 36296 3520 1252 S   0.0 0.8   1:40.49 php5-fpm

Check disk space used and available command:

df -h

This will check available space on your filesystem. Your output will likely look different depending on the configuration of your server.

root@rpi-server:~# df -h
Filesystem      Size Used Avail Use% Mounted on
rootfs          7.3G 3.7G 3.6G 51% /
/dev/root       7.3G 3.7G 3.6G 51% /
devtmpfs        212M     0 212M   0% /dev
tmpfs            44M 196K   44M   1% /run
tmpfs           5.0M     0 5.0M   0% /run/lock
tmpfs            88M     0   88M   0% /run/shm

Change Directory Command:

cd /path/to/directory

This will change the location of the directory your browsing. In the example above, simply change the path to the directory in which you need to change to. For example, if you needed to move to '/var/www', you would type 'cd /var/www'

root@rpi-server:~# cd /var/www
root@rpi-server:/var/www#

List directory content command:

ls

Now that you've moved to the directory of your choice, you may want to get a list of the content from within that directory. Simply enter the 'ls' command. You should see something like:

root@rpi-server:/var/www# ls
bill_murray.jpg check.php damncat.jpg index.php logo.png logs phpinfo.php phpmyadmin test vpsboard
Make Directory command:

mkdir ./mynewdirectory

The command above will create the directory 'mynewdirectory' in whatever directory you are currently in. Maybe you want to go deeper than that, so use the following the command:

mkdir -p ./mynewdirectory/test/testing

The command above not only creates the directory but also all that follows it.

Move a file command:

mv test.txt ./testdirectory

The above command will the file 'test.txt' to the directory 'testdirectory'. Pretty straight forward.

Change password command:

passwd

This will change the password for the user you are logged in as. For example, if you are logged in as the root password it's very good practice to change your password immediately. You will be prompted to type in your password, and asked to retype it. Your password will not show in the screen. Output will be similar to below:

root@rpi-server:~# passwd
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Check the CPU information command:

cat /proc/cpuinfo

This command will tell you information about the CPU your provider uses for the VPS node you are on. Thank you for submitting this one.

user@not-my-pi:~$ cat /proc/cpuinfo
processor   : 0
vendor_id   : GenuineIntel
cpu family   : 6
model       : 42
model name   : Intel(R) Xeon(R) CPU E31230 @ 3.20GHz
stepping   : 7
cpu MHz       : 3192.748
cache size   : 4096 KB
fdiv_bug   : no
hlt_bug       : no
f00f_bug   : no
coma_bug   : no
fpu       : yes
fpu_exception   : yes
cpuid level   : 13
wp       : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx rdtscp lm constant_tsc up arch_perfmon pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 x2apic popcnt aes xsave avx hypervisor lahf_lm
bogomips   : 6385.49
clflush size   : 64
cache_alignment   : 64
address sizes   : 40 bits physical, 48 bits virtual

Check memory information command:

cat /proc/meminfo

Likely not as used as often as the check CPU info command above, but can come in handy. Thank you for submitting this one.

user@not-my-pi:~$ cat /proc/meminfo
MemTotal: 254828 kB
MemFree: 9012 kB
Buffers: 45764 kB
Cached: 140528 kB
SwapCached: 1036 kB
Active: 139832 kB
Inactive: 88016 kB
Active(anon): 19448 kB
Inactive(anon): 22164 kB
Active(file): 120384 kB
Inactive(file): 65852 kB
Unevictable: 0 kB
Mlocked: 0 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 254828 kB
LowFree: 9012 kB
SwapTotal: 496632 kB
SwapFree: 490712 kB
Dirty: 216 kB
Writeback: 0 kB
AnonPages: 40804 kB
Mapped: 11764 kB
Shmem: 56 kB
Slab: 12616 kB
SReclaimable: 8924 kB
SUnreclaim: 3692 kB
KernelStack: 640 kB
PageTables: 700 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 624044 kB
Committed_AS: 229688 kB
VmallocTotal: 765952 kB
VmallocUsed: 5628 kB
VmallocChunk: 752772 kB
HardwareCorrupted: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 4096 kB
DirectMap4k: 12280 kB
DirectMap4M: 249856 kB

Stop/Start/Restart (most) services:

service [service name] [stop/start/restart/reload/status]
OR

/etc/init.d/[service name] [stop/start/restart/reload/status]

The examples below will use both methods to start/stop/status Nginx and MySQL as it's what is running on my Raspberry Pi right now.

root@rpi-server:~# service nginx restart
Restarting nginx: nginx.

Code:

root@rpi-server:~# service nginx status
[ ok ] nginx is running.

Code:

root@rpi-server:~# /etc/init.d/nginx stop
Stopping nginx: nginx.

Code:

root@rpi-server:~# /etc/init.d/nginx start
Starting nginx: nginx.

Code:

root@rpi-server:~# /etc/init.d/mysql status
[info] /usr/bin/mysqladmin  Ver 8.42 Distrib 5.5.31, for debian-linux-gnu on armv7l
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Server version		5.5.31-0+wheezy1
Protocol version	10
Connection		Localhost via UNIX socket
UNIX socket		/var/run/mysqld/mysqld.sock
Uptime:			12 days 16 hours 14 min 34 sec

Threads: 1  Questions: 24062  Slow queries: 0  Opens: 1532  Flush tables: 1  Open tables: 293  Queries per second avg: 0.021.

Thanks [member=wcypierre] for sharing.

Change File Permissions command:

chmod 755 file-or-directory
Need to change the file or folder permissions? Do it quickly via SSH! The example below shows me simply changing the permissions of the directory 'testdir' to 755. Thanks [member=wcypierre] for sharing.

root@rpi-server:/var/www# chmod 755 testdir
root@rpi-server:/var/www#

Please contribute to this thread!

If you wish to contribute, I'll add your responses to this original posting so all commands are in one post for easy retrieval and use. I'll link to your profile or response to give credit where it is due.

Epidrive · Aug 18, 2013

cat /proc/cpuinfo - cpu info

cat /proc/meminfo - mem info

wcypierre · Aug 18, 2013

1. at the Top command, press CTRL + M to sort the processes according to their memory usage(from highest to lowest)

2. service <service_name> <action: start/restart/stop/reload> i.e service nginx stop

3. chmod <permissions> <file/folder>

365Networks · Aug 18, 2013

How to create a tar.gz:

Code:

tar -pczf name-of-archive.tar.gz /path/to/dir

wcypierre · Aug 18, 2013

history - to show the list of commands that you've typed

Chronic · Aug 18, 2013

clear - clear the terminal display

H_Heisenberg · Aug 18, 2013

cat /etc/issue

Easy way to find out which Linux Distribution is installed on the VPS/server/machine.

Remove/disable/add/enable services in RHEL based OSs (CentOS/SL/Fedora):

Add/enable & disable:
chkconfig <servicenamehere> <option>

Options:
off - disable
on - enable/add

E.g: chkconfig httpd off (will disable httpd as a server so it won't startup with the OS)

Remove services totally:
chkconfig --del <servicename>

E.g: chkconfig --del httpd (will delete httpd completely from the service list)

Copy files:

cp <path/to/file> <path/to/destination>

For folders with files use:
cp -r <path/to/file> <path/to/destination>

-r is for recursive

There is way more that is just simply and applies for all Distros but I'm too lazy

.

Oh: "ifconfig" is good, too.

WebSearchingPro · Aug 18, 2013

uname -a

Check what linux kernel + architecture is running

setenforce 0 | 1

Disables and Enables SELinux till the system reboots (good for quick tests)

restorecon -R /path/to/dir/

Fixes issues relating to SELinux and file permissions

setsebool -P module_name=0|1

Enable or disable certain SELinux modules.

semanage port -a -t http_port_t-p tcp #

Allows using a port other than 8080|80 on a SELinux installation.

rpm --nosignature -i

Quickly add repo to RHEL distro.

cat /etc/passwd

cat /etc/group

Check users and groups on the system

su [username]

Quickly switch accounts

ls -l

Check file ownership quickly.

curl -i

{option}
{option}Check if apache/nginx/varnish is running on that particular url.

drmike · Aug 18, 2013

Get process that is running info:

ps -aux | grep ______ [where ___ = whatever you are looking for]

ex: ps -aux | grep apache

Stopping a process that is abandoned or crashed:

kill -9 [process #]

That process number comes from finding the process above.

D. Strout · Aug 18, 2013

A few more:

nano [filename] - opens the nano editor to edit the file. After editing, Ctrl + O saves the file, and Ctrl + X exits.

For testing:

dd bs=1M count=1024 if=/dev/zero of=test conv=fdatasync - copy 1GB of test stuff to the hard drive for disk speed test

wget cachefly.cachefly.net/100mb.test - Download a 100MB test file from Cachefly's CDN for network speed tests.

GIANT_CRAB · Aug 18, 2013

I can't believe you guys missed out the yum command.

Its the most powerful command ever.

This commands does everything magically for you.

yum install - Install a software via yum repo

yum update - Update all your softwares to the latest via yum repo

yum remove - Remove softwares you do not want or not longer need via yum repo

Btw, MannDude, its GNU/Linux, Linux is just a kernel. It wouldn't function without GNU.

lel

Magiobiwan · Aug 19, 2013

Don't forget htop, the BETTER top.

drmike · Aug 19, 2013

Yes, more htop

Picked htop up from Crunchbang a few releases ago and now prefer it

patz · Aug 19, 2013

Get logged in users:

who
Get current user:

who am i
It's the who command with 2 arguments, so who is it, or who mom loves all have the same results.

Get logged in users and what they are doing:

w
Get users that logged in over time, their ip, last log in time and log in duration.

Code:

last

365Networks · Aug 19, 2013

iptables drop an IP address:

Code:

iptables -A INPUT -s ADDRESSHERE -j DROP

jhadley · Aug 19, 2013

You forgot the all-important

Code:

dd

MannDude · Aug 19, 2013

Thanks for all the contributions, will be adding them to the original post later!

shawn_ky · Aug 19, 2013

wget http://mirror.nexcess.net/epel/6/i386/epel-release-6-8.noarch.rpm

rpm -ivh epel-release-*

yum install joe

<my all time favorite editor... have used it from the beginning...>

acd · Aug 20, 2013

buffalooed said:
Get process that is running info:

ps -aux | grep ______ [where ___ = whatever you are looking for]

ex: ps -aux | grep apache

More pgrep, please:

pgrep processname (see manpage for more filtering options, and there are a lot of them)

see full info for grepped processes:

ps -fp $(pgrep -d, processname)

mitgib · Aug 20, 2013

Some common commands I use that are not already listed above

lsof - list open files

lsof -i

ort ex lsof -i:80 to find if the web server is listening

lsof -pPID - what does PID have open, great for finding IO abusers after finding them in iotop

iotop - simple top-like I/O monitor

iotop -d 3 -oPk

Linux VPS cheat sheet. Linux commands for CentOS/RHEL and Ubuntu/Debian

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