FreeBSD - Practical Shell Handbook

This handbook covers day-to-day FreeBSD administration from the terminal. For shell selection and configuration see Shells in FreeBSD, for broader administration see FreeBSD as a Server, and for automation see Shell Scripting.

FreeBSD - Administration, System and Directories

FreeBSD is a complete Unix-like operating system. The base system, kernel and core userland are developed together, while third-party applications are usually installed under /usr/local.

su

Switch to another user, usually root:

su -

Use direct root sessions only when necessary. For routine work, sudo or doas can provide narrower privilege elevation.

FreeBSD version

freebsd-version
uname -a

Use freebsd-version for the installed base-system version and uname for kernel/platform information.

Important directories

/etc            base-system configuration
/usr/local/etc  third-party package configuration
/var/log        logs
/usr/home       common home location
/home           often points to /usr/home
/boot           boot files/config
/usr/local/bin  third-party user commands
/usr/local/sbin third-party admin commands

1. Shell, terminal and commands - what are you actually doing?

The terminal is the interface. The shell interprets your commands. FreeBSD commonly uses sh for root/system scripts and tcsh for some interactive accounts, but other shells can be installed.

2. pwd - where am I?

pwd

Prints the current working directory.

3. ls - what is in the directory?

ls

Important options

-l

Long listing with permissions, owner, size and timestamps:

ls -l

-a

Include hidden files:

ls -a

-h

Human-readable sizes when combined with long listing:

ls -lh

-t

Sort by modification time:

ls -lt

-S

Sort by size:

ls -lS

Most common form

ls -lah

4. cd - change directory

cd /usr/local/etc

Important variants

Parent directory

cd ..

Home directory

cd
cd ~

Previous directory

cd -

5. Relative and absolute paths

Absolute path starts at /, for example /var/log/messages. Relative path starts from the current directory.

.

Means the current directory.

..

Means the parent directory.

6. touch - create an empty file or update timestamp

touch test.txt

7. mkdir - create directories

mkdir logs

-p

Create parent directories as needed:

mkdir -p /tmp/demo/a/b

8. cp - copy

cp source.conf copy.conf

-r

Recursive directory copy:

cp -r source_dir target_dir

-i

Ask before overwrite:

cp -i file target

-v

Verbose output:

cp -v file target

Typical case

Back up a config before editing:

cp /usr/local/etc/nginx/nginx.conf /usr/local/etc/nginx/nginx.conf.bak

9. mv - move and rename

mv old.txt new.txt
mv file.txt /tmp/

-i

Prompt before overwrite.

-v

Show performed operations.

10. rm - delete

rm file.txt

-i

Prompt before removal.

-r

Remove directories recursively.

-f

Force removal without prompting for missing files.

-rf

Recursive forced removal. Treat it as dangerous because path mistakes can destroy large directory trees.

11. cat - quickly print a file

cat /etc/hosts

Good for small files. Use less for long files.

12. less - read large files comfortably

less /var/log/messages

Useful keys: / search, n next match, G end, g start, q quit.

13. head - start of a file

head file.txt

-n

head -n 20 file.txt

14. tail - end of a file

tail file.txt

-n

tail -n 50 /var/log/messages

-f

Follow a growing log:

tail -f /var/log/messages

15. grep - search text

grep error /var/log/messages

-i

Case-insensitive search.

-n

Show line numbers.

-R

Recursive directory search.

-v

Invert match.

-E

Use extended regular expressions.

Very practical

grep -RniE 'error|warning' /usr/local/etc

16. find - find files

-name

find /usr/local/etc -name '*.conf'

-iname

Case-insensitive filename match.

-type

find /var -type f
find /usr/local -type d

-mtime

Find by modification age:

find /var/log -type f -mtime -7

-size

Example:

find /var -type f -size +100M

17. which, command -v, whereis - where is a program?

which nginx
command -v sh
whereis nginx

command -v is portable shell logic; whereis also searches known source/manual locations.

18. file - what kind of file is this?

file /bin/sh
file archive.tar.gz

19. stat - detailed file information

stat file.txt

Shows size, ownership, permissions and timestamps.

20. man - command documentation

man service
man rc.conf
man 5 rc.conf

FreeBSD manual pages are first-class documentation.

21. echo - print text and variables

echo hello
echo "$HOME"

22. Redirection > and >>

> overwrites a file. >> appends.

echo test > file.txt
echo another >> file.txt

23. Pipe |

A pipe sends stdout of one command into stdin of another:

sockstat -4 -l | grep nginx

24. sort, uniq, wc

sort

sort names.txt

uniq

Usually after sort:

sort names.txt | uniq

wc

Count lines, words or bytes:

wc -l file.txt

25. whoami, id, groups

whoami
id
groups

Use these to confirm identity and group memberships before debugging permission issues.

26. who and w

who
w

Show logged-in users; w also shows activity/load information.

28. uname - kernel and platform

-a

uname -a

-r

uname -r

30. hostname

hostname

31. uptime

uptime

Shows uptime and load averages.

32. top - processes and load

top

Use it for a quick view of CPU, memory and busy processes.

33. ps - process list

ps aux

34. pgrep - find PID by name

pgrep nginx

-f

Match full command line.

-l

Show process names with PIDs.

35. kill and pkill

kill PID
pkill processname

Try normal termination before stronger signals.

36. df - free filesystem space

df -h

37. du - directory size

-s

Summary only.

-h

Human-readable sizes:

du -sh /var/*

38. mount - what is mounted?

mount

On ZFS systems, also inspect zfs list and zpool status.

40. FreeBSD - disks

Useful commands:

geom disk list
gpart show
camcontrol devlist

41. ZFS

Core checks:

zpool status
zpool list
zfs list
zfs list -t snapshot

43. FreeBSD - ifconfig

ifconfig
ifconfig -a

FreeBSD uses ifconfig as a primary network-interface tool.

44. Routing on FreeBSD

netstat -rn
route -n get default

45. ping

ping 1.1.1.1
ping example.com

If IP works but hostname does not, investigate DNS.

46. curl

curl -I https://example.com
curl -v https://example.com

47. DNS - host and dig

host example.com
dig example.com

49. FreeBSD - sockstat

Show listening sockets:

sockstat -4 -6 -l

Find a port:

sockstat -4 -6 -l | grep ':8080'

50. ssh

ssh user@server

Different port

ssh -p 2222 user@server

More diagnostics

ssh -vvv user@server

51. scp

scp file user@server:/tmp/
scp user@server:/tmp/file .

52. ssh-keygen

ssh-keygen -t ed25519

53. chmod

Add execute permission

chmod +x script.sh

Numeric mode

chmod 640 config.conf
chmod 755 script.sh

54. chown

chown user:group file

57. FreeBSD - pkg

Update catalogue

pkg update

Upgrade packages

pkg upgrade

Install

pkg install nginx

Remove

pkg delete nginx

Search

pkg search nginx

Information

pkg info nginx

All installed

pkg info

Unneeded dependencies

pkg autoremove

Which package owns a file

pkg which /usr/local/sbin/nginx

60. FreeBSD - services with service

service nginx status
service nginx start
service nginx stop
service nginx restart

Use onestart for a one-off start when the service is not enabled.

61. FreeBSD - sysrc

Read and modify rc.conf-style variables safely:

sysrc nginx_enable
sysrc nginx_enable=YES
sysrc nginx_enable=NO

62. FreeBSD - logs

Common location:

/var/log

Typical system log:

tail -f /var/log/messages

63. FreeBSD - base system and packages

Remember the separation: /etc and base tools belong to the operating system; /usr/local is where third-party packages normally live.

64. FreeBSD - base-system updates

Update method depends on FreeBSD release and deployment model. Follow the procedure documented for your supported release and read release notes before upgrades.

66. dmesg

dmesg
dmesg | tail -n 50

Useful for boot, hardware, disk and driver messages.

68. FreeBSD - sysctl

Read kernel/system parameters:

sysctl hw.ncpu
sysctl hw.physmem

Temporary changes may be possible with sysctl name=value; persistent settings belong in the correct configuration file.

69. date

date

70. history

Shows previous shell commands. Exact behavior depends on the shell.

71. Ctrl+R

In shells that support reverse history search, Ctrl+R searches previous commands interactively.

72. Keyboard shortcuts

Common terminal/shell shortcuts include Ctrl+C to interrupt, Ctrl+D for EOF/logout in many shells, Ctrl+L to clear, and Ctrl+Z to suspend a foreground job.

73. &&, ||, ;

&&

Run the next command only if the previous succeeded:

nginx -t && service nginx reload

||

Run the next command if the previous failed.

;

Run commands sequentially regardless of status.

74. Background processes

Append & to launch in background:

long-command &

For remote sessions, tmux is safer for long interactive work.

75. tmux

pkg install tmux
tmux new -s admin
tmux attach -t admin

A tmux session survives an SSH disconnect.

76. tar archives

Create:

tar -czf backup.tar.gz directory/

Extract:

tar -xzf backup.tar.gz

77. gzip, gunzip

gzip file
gunzip file.gz

78. crontab

crontab -e
crontab -l

Use cron for simple scheduled commands; FreeBSD also has the periodic framework for system maintenance.

82. Quick FreeBSD diagnostics

freebsd-version
uptime
df -h
zpool status
ifconfig
netstat -rn
sockstat -4 -6 -l
ps aux
tail -n 50 /var/log/messages

Real-life examples - FreeBSD

1. Website stopped responding

service nginx status
nginx -t
sockstat -4 -6 -l | grep ':80\|:443'
tail -n 100 /var/log/nginx/error.log
curl -v http://127.0.0.1/

2. Disk is almost full

df -h
zfs list
du -sh /var/* | sort -h

3. Check ZFS health

zpool status
zpool list
zfs list

4. You forgot where nginx configuration is

pkg info -l nginx | grep conf
find /usr/local/etc -iname '*nginx*'

5. Who uses port 8080?

sockstat -4 -6 -l | grep ':8080'

6. Network does not work

ifconfig
netstat -rn
ping 1.1.1.1
host example.com
cat /etc/resolv.conf

7. Install nginx from scratch

pkg install nginx
sysrc nginx_enable=YES
nginx -t
service nginx start
sockstat -4 -6 -l | grep nginx

8. Configuration changed and nginx will not start

nginx -t
service nginx status
tail -n 100 /var/log/nginx/error.log

Fix syntax before repeatedly restarting.

9. Application consumes CPU

top
ps aux
pgrep -af appname

10. Quick recognition of an unfamiliar server

freebsd-version
hostname
uptime
df -h
zpool status
pkg info | head
service -e
sockstat -4 -6 -l

11. Package update

pkg update
pkg upgrade

Read package messages after upgrades.

12. Classic base-system update

Follow the supported update mechanism for the installed FreeBSD release. Create a ZFS boot environment or other rollback point where appropriate before major changes.

13. Long process over SSH

tmux new -s work
long-command

Detach and later reattach instead of relying on one SSH connection.

14. Configuration backup

tar -czf /tmp/etc-backup.tar.gz /etc /usr/local/etc

For real backups, copy data off the machine and include application state/databases separately.

FreeBSD - minimal set to remember

pwd / ls / cd
cp / mv / rm
less / tail / grep / find
ps / top / kill
df / du
ifconfig / netstat / sockstat
ssh / scp
pkg
service / sysrc
zpool / zfs
dmesg / sysctl
tmux / tar / crontab

The practical FreeBSD pattern is: inspect first, use native tools, remember the /usr/local split, and read the manual page before forcing a change.

Official references

• FreeBSD Handbook: https://docs.freebsd.org/en/books/handbook/
• FreeBSD manual pages: https://man.freebsd.org/
• FreeBSD release information: https://www.freebsd.org/releases/