Cheatography
https://cheatography.com
A cheat sheet of the commands and hints I use most for Linux
Expansion
ls $(which cp)
ls `which cp`
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Command expansion |
mkdir {2017...2020}-{01-12}
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Brace expansion |
echo text ~/*.txt {a,b} $USER
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Variable expansion |
echo "text ~/*.txt {a,b} $USER"
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" expansion |
echo 'text ~/*.txt {a,b} $USER'
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' expansion (NONE) |
Redirection & Commands
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Standard Out |
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Standard Error |
ls > file.txt 2>&1
ls &> file.txt
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Standard Out & Error |
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Read stdin & writes stdout |
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Run cmd1 then cmd2 |
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Run cmd2 if cmd1 is OK |
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Run cmd2 if cmd1 is KO |
su / sudo
Become another user, ROOT
by default. If -
or -l
, load user envs and working dir. |
Execute command as user. Default root
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Execute command as user. Default root
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Which commands I'm allowed to execute
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Edit /etc/sudoers
file. Example teralco ALL=(root) NOPASSWD: /etc/init.d/jboss
teralco ALL=(jboss) NOPASSWD: /bin/kill
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UFW
ufw status [verbose|numbered]
Show status and rules
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ufw default deny incoming
ufw default allow outgoing
Deny all incoming traffic by default
Allow all outgoing traffic by default
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ufw [allow|deny] from IP to [any|interface_name] [proto tcp|udp] port PORT
Full allow/deny rule
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ufw [allow|deny] service_name
Allow/deny a service ( ssh www ftp ...
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Alt commands
/var/log/messages & /var/log/syslog
System log files
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Record session commands in file
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Keep command running even after close session
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tar -Jxvf file.tar.xz [-C dest_folder]
Extract xz (higher compress ratio)
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zip -FF x.zip --out Y.zip && unzip Y.zip
Merge zip files (x.zip, x.z01, x.z02)
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Higher memory consumption processes
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List partition tables
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dd bs=4M if=input.iso of=/dev/sd? conv=fdatasync
Burn iso in device
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Searches
find path -name *.log -type f -mtime +5 -exec rm -rvf {} \;
Find and delete files older than 5 days
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find path -type f -printf "%s\t%p\n" | sort -rn | head -10
Find the 10 biggest files
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grep -rlie 'pattern' path
Find files with pattern content
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du -cks path/* | sort -rn | head -10
Find biggest dirs
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Dir size
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Permissions
chmod [u|g|o][+|-|=][rwx] dir_file
Change permissions
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Set uid. File is always exec as owner user
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Set gid. New files in folder are always owned by folder owner
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Sticky Bit. Files in dir can only be renamed or removed by owner or root
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Set default permissions to dirs
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Enviroment
/etc/profile
/etc/bash.bashrc
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Global env config files |
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User env config file |
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Print defined env vars |
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Show defined aliases |
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Make a VAR available to child process |
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Load a file into current script or shell session |
Network
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Show ips
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ifup|ifdown interface_name
Up or down an interface
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/etc/network/interfaces
File interfaces are defined
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hostnamectl [set-hostname hostname]
Manage hostname ( /etc/hostname
) without restarting |
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All tcp and udp listening ports
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All tcp and udp listening ports
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Scan port in host
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SSH
ssh-keygen [-f /etc/ssh/ssh_host_rsa_key] -t rsa -b 4096
Generate ssh rsa key. By default ~/.ssh/id_rsa
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ssh-copy-id [-i ~/.ssh/mykey] user@host
Copy ssh key in remote host ( ~/.ssh/authorized_keys
). By default ~/.ssh/id_rsa
. |
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Exec command in host
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Connect to hostB through hostA (Jumping). Identification in localhost. Can use ProxyJump
in ~/.ssh/config
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ssh -D port -fCqN user@host
Proxy socket (HTTP and HTTPS traffic) through port.
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ssh -nNT -L 9000:remote_server:80 user@host
Tunneling (Local port forwarding). Map remote_server:80
into localhost:9000
through host |
ssh -nNT -R 9000:localhost:3000 user@host
Tunneling (Remote port forwarding). Map localhost:3000
into host:9000
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Comments
Nice, I will use it.
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