What do you do if you just installed a fresh Ubuntu 20.04 server, and after installing some packages with "apt" you notice high CPU usage from the swap process?
If "top" shows kswapd0 persistently using high CPU, and "freemem -d" and
swap are ok, you can try to adjust the swappiness in file sysctl.conf
and reboot.
$ cat /proc/sys/vm/swappiness
60
$ sudo vi /etc/sysctl.conf
$ cat /etc/sysctl.conf | grep vm
vm.swappiness=10
Changing swappiness didn't fix this problem of high CPU usage. Let's dig deep.
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04 LTS
Release: 20.04
Codename: focal
install@d990 ~ $ uname -a
Linux d990 5.4.0-29-generic #33-Ubuntu SMP Wed Apr 29 14:32:27 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Look closely at "top" output.
$ top
top - 19:03:26 up 7 min, 3 users, load average: 3.09, 2.72, 1.44
Tasks: 132 total, 1 running, 131 sleeping, 0 stopped, 0 zombie
%Cpu(s): 76.3 us, 0.4 sy, 0.0 ni, 23.2 id, 0.1 wa, 0.0 hi, 0.0 si, 0.0 st
MiB Mem : 15892.2 total, 10206.3 free, 4412.8 used, 1273.1 buff/cache
MiB Swap: 4096.0 total, 4096.0 free, 0.0 used. 11199.7 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1071 kevin 20 0 2435108 2.3g 1480 S 300.0 14.7 20:50.80 kswapd0 1147 minec 20 0 7861400 1.9g 28544 S 6.6 11.9 1:54.40 java
1 root 20 0 167604 11524 8368 S 0.0 0.1 0:00.98 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_gp
4 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_par+
6 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kworker+
8 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 mm_perc+
9 root 20 0 0 0 0 S 0.0 0.0 0:00.01 ksoftir+
10 root 20 0 0 0 0 I 0.0 0.0 0:00.13 rcu_sch+
11 root rt 0 0 0 0 S 0.0 0.0 0:00.00 migrati+
12 root -51 0 0 0 0 S 0.0 0.0 0:00.00 idle_in+
13 root 20 0 0 0 0 I 0.0 0.0 0:00.01 kworker+
14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuhp/0
15 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cpuhp/1
16 root -51 0 0 0 0 S 0.0 0.0 0:00.00 idle_in+
17 root rt 0 0 0 0 S 0.0 0.0 0:00.14 migrati+
$ top -u kevin
top - 19:03:59 up 8 min, 3 users, load average: 3.05, 2.75, 1.49
Tasks: 132 total, 1 running, 131 sleeping, 0 stopped, 0 zombie
%Cpu(s): 76.3 us, 0.3 sy, 0.0 ni, 23.1 id, 0.3 wa, 0.0 hi, 0.0 si, 0.0 st
MiB Mem : 15892.2 total, 10205.5 free, 4413.5 used, 1273.2 buff/cache
MiB Swap: 4096.0 total, 4096.0 free, 0.0 used. 11199.0 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1071 kevin 20 0 2435108 2.3g 1480 S 300.3 14.7 22:28.66 kswapd0
1015 kevin 20 0 14368 6760 2800 S 0.0 0.0 0:00.00 rsync
Why is kevin in charge of swap? Kevin has yet to log in to the system.
$ last kevin
wtmp begins Sat May 9 18:16:21 2020
$ groups kevin
kevin : kevin
$ sudo grep kevin /etc/sudoers
$ ps -fu kevin
UID PID PPID C STIME TTY TIME CMD
kevin 1015 1 0 18:56 ? 00:00:00 rsync
kevin 1071 1 99 18:56 ? 00:11:53 ./kswapd0
We know kevin has not logged in, is only in his own group, and does not have sudo. This was the most recent account we created on the machine.
$ tail -1 /etc/passwd
kevin:x:1005:1004:,,,,novice tech learner:/home/kevin:/bin/bash
Comment out the entry in the passwd file.
$ tail -1 /etc/passwd
kevin:x:1005:1004:,,,,novice tech learner:/home/kevin:/bin/bash
$ sudo vi /etc/passwd
$ tail -1 /etc/passwd
#kevin:x:1005:1004:,,,,novice tech learner:/home/kevin:/bin/bash
Run top, and it won't know the "kevin" username for uid 1005. It is still consuming CPU.
$ top
top - 19:08:43 up 13 min, 3 users, load average: 3.13, 2.96, 1.92
Tasks: 130 total, 1 running, 129 sleeping, 0 stopped, 0 zombie
%Cpu(s): 76.2 us, 0.6 sy, 0.0 ni, 23.0 id, 0.3 wa, 0.0 hi, 0.0 si, 0.0 st
MiB Mem : 15892.2 total, 10198.5 free, 4413.8 used, 1279.9 buff/cache
MiB Swap: 4096.0 total, 4096.0 free, 0.0 used. 11198.6 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1071 1005 20 0 2435108 2.3g 1480 S 300.7 14.7 36:40.32 kswapd0
1147 minec 20 0 7861400 1.9g 28544 S 6.7 11.9 2:14.81 java
375 root 20 0 0 0 0 S 0.3 0.0 0:00.01 jbd2/sd+
1 root 20 0 167604 11524 8368 S 0.0 0.1 0:01.00 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_gp
4 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_par+
6 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kworker+
8 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 mm_perc+
With the passwd entry for kevin commented out, let's reboot and observe what happens.
$ sudo systemctl reboot
$ top
top - 19:14:04 up 1 min, 1 user, load average: 1.35, 0.61, 0.23
Tasks: 138 total, 1 running, 137 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.3 us, 0.4 sy, 0.0 ni, 99.3 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
MiB Mem : 15892.2 total, 12795.1 free, 1850.3 used, 1246.8 buff/cache
MiB Swap: 4096.0 total, 4096.0 free, 0.0 used. 13763.3 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
898 minec 20 0 7861400 1.7g 28288 S 6.3 10.7 1:20.07 java
156 root 20 0 0 0 0 I 0.3 0.0 0:00.16 kworker+
443 root 19 -1 133560 61216 60108 S 0.3 0.4 0:00.61 systemd+
1206 root 20 0 13416 8268 7096 S 0.3 0.1 0:00.01 sshd
1207 sshd 20 0 12160 4616 3708 S 0.3 0.0 0:00.01 sshd
1 root 20 0 167744 11508 8440 S 0.0 0.1 0:03.25 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_gp
4 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_par+
Let's remove the kevin account properly. Uncomment the line in /etc/passwd and delete the account.
$ sudo vi /etc/passwd
$ sudo userdel -r kevin
$ grep kevin /etc/passwd
$ uptime
19:15:53 up 3 min, 1 user, load average: 0.21, 0.42, 0.20
Reboot and look for normal functioning.
$ sudo systemctl reboot
Sunday, May 10, 2020
Install Ubuntu 20.04 Server
The server version of Ubuntu had previously been tuned for server-oriented workloads. This is reportedly no longer the case, so a primary difference between Ubuntu 20 server and desktop is that server lacks a graphical user interface.
Download an image from the Ubuntu releases page. Most everything is 64 bit. Note that "AMD" means it works on the AMD and Intel instruction sets. You can use the AMD64 image on a modern Intel CPU.
Burn the image to a DVD or other mountable storage. Boot the machine from the storage. This install will use hard-wired Ethernet and a static IP address. If you have a real (typically non-consumer internet service) domain name, use that as the "search domain".
Disable printing of Ubuntu newswire during shell logon.
Download an image from the Ubuntu releases page. Most everything is 64 bit. Note that "AMD" means it works on the AMD and Intel instruction sets. You can use the AMD64 image on a modern Intel CPU.
Burn the image to a DVD or other mountable storage. Boot the machine from the storage. This install will use hard-wired Ethernet and a static IP address. If you have a real (typically non-consumer internet service) domain name, use that as the "search domain".
This is a server install, so maybe you do not want "games" in your search path. Backup the "environment" file then remove the games directory from the search path.
$ sudo mv /etc/environment /etc/environment.orig
$ sudo vi /etc/environment
$ cat /etc/environment
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
Modify the shell login files in your home directory.
$ cd ~
$ cp -p .bashrc .bashrc.orig
$ mv .profile .profile.orig
$ mv .bashrc .bash_profile
Remove colorization by setting TERM environment variable in .bash_profile.
$ echo $TERM
xterm-256color
$ export TERM=xterm-mono
Edit .bash_profile and put in a bit of color to the command prompt variable PS1.
$ grep 033 ~/.bash_profile
PS1='\[\033[01;32m\]\u@\h\[\033[00m\] \w \$ '
Put the present working directory at the end of the PATH variable. Add this to file .bash_profile.
export PATH=$PATH:.
Remove shell's suggestions for a mis-typed command. Add this to file .bash_profile.
unset command_not_found_handle
Then "source" the login files or simply log out and log in again.
$ ./.bash_profile
Get familiar with the install and the machine.
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04 LTS
Release: 20.04
Codename: focal
$ uname -a
Linux d990 5.4.0-26-generic #30-Ubuntu SMP Mon Apr 20 16:58:30 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
$ lspci
00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
00:16.0 Communication controller: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 (rev 04)
00:16.3 Serial controller: Intel Corporation 6 Series/C200 Series Chipset Family KT Controller (rev 04)
00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network Connection (Lewisville) (rev 04)
00:1a.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 (rev b4)
00:1c.2 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 3 (rev b4)
00:1d.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 (rev 04)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev a4)
00:1f.0 ISA bridge: Intel Corporation Q67 Express Chipset LPC Controller (rev 04)
00:1f.2 RAID bus controller: Intel Corporation SATA Controller [RAID mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller (rev 04)
$ df -k
Filesystem 1K-blocks Used Available Use% Mounted on
udev 8093172 0 8093172 0% /dev
tmpfs 1627360 1204 1626156 1% /run
/dev/sda2 1921800384 9591096 1814517336 1% /
tmpfs 8136796 0 8136796 0% /dev/shm
tmpfs 5120 0 5120 0% /run/lock
tmpfs 8136796 0 8136796 0% /sys/fs/cgroup
/dev/loop0 27776 27776 0 100% /snap/snapd/7264
/dev/loop1 56320 56320 0 100% /snap/core18/1705
/dev/loop2 70656 70656 0 100% /snap/lxd/14804
tmpfs 1627356 0 1627356 0% /run/user/1000
Familiarize yourself with the network configuration.
$ ls -l /etc/netplan
total 4
-rw-r--r-- 1 root root 280 May 10 00:03 00-installer-config.yaml
$ cat /etc/netplan/00-installer-config.yaml
# This is the network config written by 'subiquity'
network:
ethernets:
enp0s25:
addresses:
- 192.168.0.9/24
gateway4: 192.168.0.1
nameservers:
addresses:
- 1.1.1.1
- 8.8.8.8
search:
- duckdns.org
version: 2
Look at the syslog.
$ sudo tail /var/log/syslog
Look at the running processes, then look at running services.
$ ps -ef | more
$ systemctl list-units --all --type=service --no-pager
Let's remove a service we don't want automatically started, and one we don't need.
$ sudo systemctl stop rsync
$ sudo systemctl disable rsync
$ systemctl status vgauth
● vgauth.service - Authentication service for virtual machines hosted on VMware
Loaded: loaded (/lib/systemd/system/vgauth.service; enabled; vendor preset: enabled)
Active: inactive (dead)
Condition: start condition failed at Sun 2020-05-10 00:16:27 UTC; 2h 30min ago
Docs: http://github.com/vmware/open-vm-tools
May 10 00:16:27 d990 systemd[1]: Condition check resulted in Authentication service for virtual machines hosted on VMware being skipped.
$ sudo systemctl stop vgauth
$ sudo systemctl disable vgauth
$ systemctl status open-vm-tools
● open-vm-tools.service - Service for virtual machines hosted on VMware
Loaded: loaded (/lib/systemd/system/open-vm-tools.service; enabled; vendor preset: enabled)
Active: inactive (dead)
Condition: start condition failed at Sun 2020-05-10 02:56:23 UTC; 3min 54s ago
Docs: http://open-vm-tools.sourceforge.net/about.php
May 10 02:56:23 d990 systemd[1]: Condition check resulted in Service for virtual machines hosted on VMware being skipped.
$ sudo systemctl stop open-vm-tools
[sudo] password for install:
$ sudo systemctl disable open-vm-tools
Synchronizing state of open-vm-tools.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install disable open-vm-tools
Removed /etc/systemd/system/multi-user.target.wants/open-vm-tools.service.
$ systemctl status open-vm-tools
● open-vm-tools.service - Service for virtual machines hosted on VMware
Loaded: loaded (/lib/systemd/system/open-vm-tools.service; indirect; vendor preset: enabled)
Active: inactive (dead)
Docs: http://open-vm-tools.sourceforge.net/about.php
May 10 02:56:23 d990 systemd[1]: Condition check resulted in Service for virtual machines hosted on VMware being skipped.
This is a server machine, so we don't need this process attaching to a sound card.
$ apt list pulseaudio
Listing... Done
pulseaudio/focal-updates 1:13.99.1-1ubuntu3.5 amd64 [upgradable from: 1:13.99.1-1ubuntu3.3]
N: There are 3 additional versions. Please use the '-a' switch to see them.
$ sudo apt remove pulseaudio
Since this is a server install, the majority of the time it will be accessed remotely. A person using an X display may want to work with images, so install an image viewer such as eog.
$ sudo apt install eog
$ sudo chmod -x /etc/update-motd.d/50-motd-news
Note the firewall is not active.
$ sudo ufw status
Status: inactive
Install software updates. You may need to reboot the machine to apply all software updates.
$ sudo apt update
$ sudo apt upgrade
$ sudo systemctl reboot
Familiarize yourself with users and groups.
$ cat /etc/passwd
$ cat /etc/group
Put in users and groups.
$ sudo addgroup minecrft
Adding group `minecrft' (GID 1001) ...
Done.
$ sudo adduser minec --ingroup minecrft
Adding user `minec' ...
Adding new user `minec' (1001) with group `minecrft' ...
On a consumer-type internet connection, you may want to configure a dynamic DNS service such as DuckDNS. Create the user, get your information from duckdns.org, then configure software.
$ sudo addgroup duckdns
$ sudo adduser duckdns --ingroup duckdns
Read this to configure the software and crontab entry for duckdns.
Let's change the time zone to Amsterdam.
$ cat /etc/timezone
Etc/UTC
$ timedatectl
Local time: Sun 2020-05-10 19:12:56 UTC
Universal time: Sun 2020-05-10 19:12:56 UTC
RTC time: Sun 2020-05-10 19:12:56
Time zone: Etc/UTC (UTC, +0000)
System clock synchronized: yes
NTP service: active
RTC in local TZ: no
$ timedatectl list-timezones | grep -i ams
Europe/Amsterdam
$ sudo timedatectl set-timezone Europe/Amsterdam
$ cat /etc/timezone
Europe/Amsterdam
$ timedatectl
Local time: Sun 2020-05-10 21:14:02 CEST
Universal time: Sun 2020-05-10 19:14:02 UTC
RTC time: Sun 2020-05-10 19:14:02
Time zone: Europe/Amsterdam (CEST, +0200)
System clock synchronized: yes
NTP service: active
RTC in local TZ: no
While we could try to disable the cloud initialization with
$ touch /etc/cloud/cloud-init-disabled
Let's remove it.
$ sudo apt remove cloud-init
Optionally, install X server.
$ sudo apt install tightvncserver
$ sudo apt install xterm
Then configure your .Xresources file.
Optionally, install javascript runtime via apt.
$ sudo apt install nodejs
$ which node
/usr/bin/nodejs
$ nodejs --version
v10.19.0
$ sudo apt install chromium-browser
$ which chromium-browser
/usr/bin/chromium-browser
Optionally, upgrade the node software.
$ curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -
$ sudo apt install nodejs
$ which node
/usr/bin/node
$ node -v
v12.16.3
$ npm -v
6.14.4
Anyone editing files with vim (vi is typically vim) may want to learn the basics of the .vimrc startup file.
$ cat ~/.vimrc
syntax off
set showmatch
set hlsearch
set matchpairs+=<:>,(:),{:},[:]
:nmap <F1> <nop>
For a graphical editor, install nedit.
$ sudo apt install nedit
Familiarize yourself with memory and disk space, network interfaces and networking, and how the machine is running. Review the output from the following commands.
Since ifconfig is deprecated, use the ip command. Instead of traceroute, use the mtr command.
$ free -m
$ df -k
$ sudo lshw
$ landscape-sysinfo
$ top
$ htop
$ ip a
$ mtr wunderground.com
__________________________________________________________
Update of this blog post with more readable explanation of network settings to be used during install from the console. These examples use IP address 192.168.0.6.
$ ls -l /etc/netplan
total 4
-rw-r--r-- 1 root root 260 Oct 16 21:13 00-installer-config.yaml
$ cat /etc/netplan/*
# This is the network config written by 'subiquity'
network:
ethernets:
enp5s0:
addresses:
- 192.168.0.6/24
gateway4: 192.168.0.1
nameservers:
addresses:
- 1.1.1.1
- 8.8.8.8
search: []
version: 2
$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp5s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether bc:30:5b:e7:a4:f9 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.6/24 brd 192.168.0.255 scope global enp5s0
valid_lft forever preferred_lft forever
inet6 fe80::be30:5bff:fee7:a4f9/64 scope link
valid_lft forever preferred_lft forever
Sunday, April 26, 2020
Install Apache On Ubuntu Linux
Install the Apache web server on Ubuntu Linux. You will need to be able to install software and start services, so this example uses a Linux account with full sudo. In this example the Linux user name is "testuser".
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.4 LTS
Release: 18.04
Codename: bionic
$ hostname -I
192.168.0.9
$ sudo ufw status
Status: inactive
# Update package list and install Apache.
$ sudo apt update
...
Fetched 2,854 kB in 2s (1,395 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
$ sudo apt install apache2
...
Created symlink /etc/systemd/system/multi-user.target.wants/apache2.service → /lib/systemd/system/apache2.service.
Created symlink /etc/systemd/system/multi-user.target.wants/apache-htcacheclean.service → /lib/systemd/system/apache-htcacheclean.service.
...
# Note the screen output shows symlinks in the configuration directories for the system services.
# Let's see what was is running.
$ systemctl status apache2.service
● apache2.service - The Apache HTTP Server
Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
Drop-In: /lib/systemd/system/apache2.service.d
└─apache2-systemd.conf
Active: active (running) since Sun 2020-04-26 12:08:28 MDT; 2min 6s ago
Main PID: 29916 (apache2)
Tasks: 55 (limit: 4915)
CGroup: /system.slice/apache2.service
├─29916 /usr/sbin/apache2 -k start
├─29918 /usr/sbin/apache2 -k start
└─29919 /usr/sbin/apache2 -k start
# Use a web browser to go to the machine name or IP address.
# Earlier you found the IP address by typing "hostname -I".
# It is kind of the developers and package maintainers to put instructions on the home page!
# Let's look at the index.html file.
$ cd /var/www/html
$ ls -l
total 12
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html
# Being owned by root, we can guess an "apache" unix logon was not created.
$ grep apa /etc/passwd
# Nothing found. Also look at last line of /etc/passwd for a new entry.
$ tail -1 /etc/passwd
# Since software often has errors, bugs, and security holes, an attacker may exploit those
# holes and possibly gain access as the user which is running the software.
# The apache software is being run as root. It had better be perfect software!
# Let's look further.
$ ps -ef | grep apache
root 29916 1 0 12:08 ? 00:00:00 /usr/sbin/apache2 -k start
www-data 29918 29916 0 12:08 ? 00:00:00 /usr/sbin/apache2 -k start
www-data 29919 29916 0 12:08 ? 00:00:00 /usr/sbin/apache2
# Processes are running both as root and as the pre-existing unix logon www-data.
# Let's see if www-data is a less-privileged account than root
$ groups www-data
www-data : www-data
$ sudo grep www /etc/sudoers
# No output from grep, so it looks like www-data doesn't have sudo. This is good.
# To open a listening connection on a "low numbered port", you typically need to be root.
# Maybe that is why part of the web server is started as root. This is something to further explore.
# For now, let's change the static web page served from the file index.html.$ cd /var/www/html
$ ls -l
total 12
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html
$ sudo cp index.html index.html.orig
$ ls -l
total 24
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html
-rw-r--r-- 1 root root 10918 Apr 26 12:29 index.html.orig
# Edit the file and add some text. When editing the file, search for "welcome" and change the text.
$ sudo vi index.html
# In the "content_section_text", you may want to add a new paragraph tags and a couple lines such as:
# Reload your web browser to see your changes.
# Verify that systemctl is set up properly to start and stop the web server.
$ sudo systemctl stop apache2.service
$ ps -ef|grep apac
testuser 32236 28823 0 14:58 pts/0 00:00:00 grep apac
$ sudo systemctl start apache2.service
$ ps -ef | grep apac
root 32262 1 0 14:58 ? 00:00:00 /usr/sbin/apache2 -k start
www-data 32264 32262 0 14:58 ? 00:00:00 /usr/sbin/apache2 -k start
www-data 32265 32262 0 14:58 ? 00:00:00 /usr/sbin/apache2 -k start
testuser 32327 28823 0 14:58 pts/0 00:00:00 grep apac
$ systemctl status apache2.service
● apache2.service - The Apache HTTP Server
Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
Drop-In: /lib/systemd/system/apache2.service.d
└─apache2-systemd.conf
Active: active (running) since Sun 2020-04-26 14:58:53 MDT; 17s ago
Process: 32214 ExecStop=/usr/sbin/apachectl stop (code=exited, status=0/SUCCESS)
Process: 32242 ExecStart=/usr/sbin/apachectl start (code=exited, status=0/SUCCESS)
Main PID: 32262 (apache2)
Tasks: 55 (limit: 4915)
CGroup: /system.slice/apache2.service
├─32262 /usr/sbin/apache2 -k start
├─32264 /usr/sbin/apache2 -k start
└─32265 /usr/sbin/apache2 -k start
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.4 LTS
Release: 18.04
Codename: bionic
$ hostname -I
192.168.0.9
$ sudo ufw status
Status: inactive
# Update package list and install Apache.
$ sudo apt update
...
Fetched 2,854 kB in 2s (1,395 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
$ sudo apt install apache2
...
Created symlink /etc/systemd/system/multi-user.target.wants/apache2.service → /lib/systemd/system/apache2.service.
Created symlink /etc/systemd/system/multi-user.target.wants/apache-htcacheclean.service → /lib/systemd/system/apache-htcacheclean.service.
...
# Note the screen output shows symlinks in the configuration directories for the system services.
# Let's see what was is running.
$ systemctl status apache2.service
● apache2.service - The Apache HTTP Server
Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
Drop-In: /lib/systemd/system/apache2.service.d
└─apache2-systemd.conf
Active: active (running) since Sun 2020-04-26 12:08:28 MDT; 2min 6s ago
Main PID: 29916 (apache2)
Tasks: 55 (limit: 4915)
CGroup: /system.slice/apache2.service
├─29916 /usr/sbin/apache2 -k start
├─29918 /usr/sbin/apache2 -k start
└─29919 /usr/sbin/apache2 -k start
# Use a web browser to go to the machine name or IP address.
# Earlier you found the IP address by typing "hostname -I".
# It is kind of the developers and package maintainers to put instructions on the home page!
# Let's look at the index.html file.
$ cd /var/www/html
$ ls -l
total 12
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html
# Being owned by root, we can guess an "apache" unix logon was not created.
$ grep apa /etc/passwd
# Nothing found. Also look at last line of /etc/passwd for a new entry.
$ tail -1 /etc/passwd
# Since software often has errors, bugs, and security holes, an attacker may exploit those
# holes and possibly gain access as the user which is running the software.
# The apache software is being run as root. It had better be perfect software!
# Let's look further.
$ ps -ef | grep apache
root 29916 1 0 12:08 ? 00:00:00 /usr/sbin/apache2 -k start
www-data 29918 29916 0 12:08 ? 00:00:00 /usr/sbin/apache2 -k start
www-data 29919 29916 0 12:08 ? 00:00:00 /usr/sbin/apache2
# Processes are running both as root and as the pre-existing unix logon www-data.
# Let's see if www-data is a less-privileged account than root
$ groups www-data
www-data : www-data
$ sudo grep www /etc/sudoers
# No output from grep, so it looks like www-data doesn't have sudo. This is good.
# To open a listening connection on a "low numbered port", you typically need to be root.
# Maybe that is why part of the web server is started as root. This is something to further explore.
# For now, let's change the static web page served from the file index.html.$ cd /var/www/html
$ ls -l
total 12
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html
$ sudo cp index.html index.html.orig
$ ls -l
total 24
-rw-r--r-- 1 root root 10918 Apr 26 12:08 index.html
-rw-r--r-- 1 root root 10918 Apr 26 12:29 index.html.orig
# Edit the file and add some text. When editing the file, search for "welcome" and change the text.
$ sudo vi index.html
# In the "content_section_text", you may want to add a new paragraph tags and a couple lines such as:
<p>
“I'm a great believer in luck, and I find the harder I work the more I have of it.”
<a href="https://plato.stanford.edu/entries/jefferson">Thomas Jefferson</a>
</p>
# Verify that systemctl is set up properly to start and stop the web server.
$ sudo systemctl stop apache2.service
$ ps -ef|grep apac
testuser 32236 28823 0 14:58 pts/0 00:00:00 grep apac
$ sudo systemctl start apache2.service
$ ps -ef | grep apac
root 32262 1 0 14:58 ? 00:00:00 /usr/sbin/apache2 -k start
www-data 32264 32262 0 14:58 ? 00:00:00 /usr/sbin/apache2 -k start
www-data 32265 32262 0 14:58 ? 00:00:00 /usr/sbin/apache2 -k start
testuser 32327 28823 0 14:58 pts/0 00:00:00 grep apac
$ systemctl status apache2.service
● apache2.service - The Apache HTTP Server
Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
Drop-In: /lib/systemd/system/apache2.service.d
└─apache2-systemd.conf
Active: active (running) since Sun 2020-04-26 14:58:53 MDT; 17s ago
Process: 32214 ExecStop=/usr/sbin/apachectl stop (code=exited, status=0/SUCCESS)
Process: 32242 ExecStart=/usr/sbin/apachectl start (code=exited, status=0/SUCCESS)
Main PID: 32262 (apache2)
Tasks: 55 (limit: 4915)
CGroup: /system.slice/apache2.service
├─32262 /usr/sbin/apache2 -k start
├─32264 /usr/sbin/apache2 -k start
└─32265 /usr/sbin/apache2 -k start
If you run the firewall, remember to allow incoming pages to apache webserver.
$ sudo ufw enable
$ sudo ufw allow www
$ sudo ufw allow www
Subscribe to:
Posts (Atom)