Find the largest file in /var
find /var/log -type f -exec du -m {} \;|sort -nr|head
Find largest directories in root
sudo du -h / --max-depth=1
Find largest directories in current directory
sudo du -h . --max-depth=1
Show largest "N" files in a directory
du -ak /var | sort -rn | head -n <N>
du -ak . | sort -rn | head -n 15
Find the largest file in /var:
find /var -type f -exec du -m {} \;|sort -nr|head
{} expands the name of file and \; ends the expression
This moves the first 91 files from current directory to /mnt/media/movies
find . -maxdepth 1 -type f |head -91|xargs cp -t "/mnt/media/movies"
Find and remove files larger than 16 GB
find . -size +16G -delete
Check size of current directory
du -sh
Disk space usage by directory
du / |sort -nr > diskusage.txt
Exclude a directory from du -sh
du -sh --exclude=./tank/media/tv/Stargate\ SG-1 /tank/media/tv
Copy files recursively, showing progress
rsync -Pavr /tank/media/movies /mnt/media/movies
Copy files recursively, showing progress, do not copy a source if it already exists at destination
rsync -Pavr --ignore-existing /mnt/media/movies /mnt/seagate6/
Create a screen session named rsync
screen -S rsync
Detach screen with Ctrl+a + d
Re-attach with screen -d -r
Kill screen
screen -X -S [session # you want to kill] quit
Find the difference between two directories method #1
diff <(cd /mnt/media/movies; find .) <(cd /mnt/seagate6/movies; find .)
Find the difference between two directories method #2
find /mnt/media/movies/ -type f -exec md5sum {} \; > dir1.txt
find /mnt/seagate6/movies/ -type f -exec md5sum {} \; > dir2.txt
Then compare the result two files with "diff":
diff dir1.txt dir2.txt
This strategy is very useful when the two directories to be compared are not in the same machine and you need to make sure that the files are equal in both directories.
Verify which ports are listening
sudo nmap -sT -O localhost
To view only the processes owned by a specific user, use the following command:
top -U [USERNAME]
ssh-keygen -f ~/.ssh/nov19_ecdsa -t ecdsa -b 521
.ssh directory: 700 (drwx------)
public key (.pub file): 644 (-rw-r--r--)
private key (id_rsa): 600 (-rw-------)Lastly your home directory should not be writeable by the group or others (at most 755 (drwxr-xr-x)).
Home folder: group can read, user can write.
chmod 755 ~
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys
chmod 600 ~/.ssh/id_rsa
chmod 644 ~/.ssh/*.pubFor all of the below commands, you can preface it with sed -i and omit > temp.txt in order to perform an "in place" modification.
Find PermitRootLogin, remove octothorpe if there is one, replace after with no
sed 's/#\?\(PermitRootLogin\s*\).*$/\1 no/' /etc/ssh/sshd_config > temp.txt
mv -f temp.txt /etc/ssh/sshd_config
Set GSSAPIAuthentication to no
sed 's/#\?\(GSSAPIAuthentication\s*\).*$/\1 no/' /etc/ssh/sshd_config > temp.txt
mv -f temp.txt /etc/ssh/sshd_config
Set interval to 120
sed 's/#\?\(ClientAliveInterval\s*\).*$/\1 120/' /etc/ssh/sshd_config > temp.txt
mv -f temp.txt /etc/ssh/sshd_config
Set countmax to 720
sed 's/#\?\(ClientAliveCountMax\s*\).*$/\1 720/' /etc/ssh/sshd_config > temp.txt
mv -f temp.txt /etc/ssh/sshd_config
Do all of the above all at once
sudo sed 's/#\?\(PermitRootLogin\s*\).*$/\1no/; s/#\?\(GSSAPIAuthentication\s*\).*$/\1no/; s/#\?\(ClientAliveInterval\s*\).*$/\1120/; s/#\?\(ClientAliveCountMax\s*\).*$/\1720/' \/etc/ssh/sshd_config > temp.txt
sudo mv -f temp.txt /etc/ssh/sshd_config && sudo systemctl restart sshd
sudo vi /etc/network/interfaces
Create a bond0 network interface
address 10.1.20.24
gateway 10.1.20.1
netmask 255.255.255.0
dns-nameservers 10.1.20.1
dns-search paw.blue
bond-slaves enp1s0f1 enp1s0f0
bond-mode 4
bond-miimon 100
bond-downdelay 200
bond-updelay 200auto bond0
iface bond0 inet static
post-up ifenslave bond0 enp1s0f0 enp1s0f1
pre-down ifenslave -d bond0 enp1s0f0 enp1s0f1
auto enp1s0f0
iface enp1s0f0 inet manual
bond-master bond0
auto enp1s0f1
iface enp1s0f1 inet manual
bond-master bond0
sudo ip link show
sudo nano /etc/network/interfaces
# The loopback network interface
auto lo
iface lo inet loopback
# The aggregated link
auto bond0
iface bond0 inet static
address 10.1.20.20
gateway 10.1.20.1
netmask 255.255.255.0
dns-nameservers 10.1.20.1
dns-search paw.blue
bond-mode 4
bond-miimon 100
bond-downdelay 50
bond-updelay 50
bond-lacp-rate fast
bond-slaves enp1s0f0 enp1s0f1
bond-xmit_hash_policy 1
auto enp1s0f0
iface enp1s0f0 inet manual
bond-master bond0
auto enp1s0f1
iface enp1s0f1 inet manual
bond-master bond0sudo ip link show
sudo vi /etc/netplan/whatever-it-is.yml
# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
version: 2
renderer: networkd
ethernets:
enp1s0f0:
dhcp4: false
dhcp6: false
optional: true
enp1s0f1:
dhcp4: false
dhcp6: false
optional: true
bonds:
bond0:
dhcp4: false
dhcp6: false
interfaces:
- enp1s0f0
- enp1s0f1
addresses: [10.1.20.24/24]
gateway4: 10.1.20.1
nameservers:
search: paw.blue
addresses: [10.1.20.1, 1.1.1.1]
parameters:
mode: 802.3adUpdate the network interface with the following:
cloud-init clean -reboot
You can do the following to remove an IP from an interface. For example, I accidentally assigned 10.1.20.24/24 to enp1s0f1 but I want that IP on enp1s0f0 instead:
sudo ip address del 10.1.20.20/24 dev enp1s0f1
You can do the following to restart an interface:
sudo ip link set enp1s0f1 down && sudo ip link set enp1s0f1 up
Fix 127.0.0.53 being in resolv.conf:
sudo rm -f /etc/resolv.conf
sudo apt install samba-common-bin samba samba-common python-glade2 system-config-samba -y
sudo mv /etc/samba/smb.conf /etc/samba/smb.conf.bak
sudo nano /etc/samba/smb.conf
#============================ Global definition ================================
[global]
workgroup = LYON
server string = Samba Server %v
netbios name = lyra
security = user
map to guest = bad user
name resolve order = bcast host
dns proxy = no
bind interfaces only = yes
#============================ Share Definitions ==============================
[User]
path = /home/nova
browsable = yes
read only = no
directory mask = 0700
create mask = 0700
valid users = will nova
[Movies]
path = /tank/media/movies
browsable = yes
read only = no
directory mask = 0775
create mask = 0775
valid users = will nova
[TV]
path = /storage/media/tv
browsable = yes
read only = no
directory mask = 0775
create mask = 0775
valid users = will nova
[Data]
path = /tank/data
browsable = yes
read only = no
directory mask = 0700
create mask = 0700
valid users = will
[Backups]
path = /storage/backup
browsable = yes
read only = no
directory mask = 0777
create mask = 0777
valid users = willThen do this after doing that file:
sudo smbpasswd -a will
sudo service smbd restart
sudo apt install snmpd
Edit community and edit agent string
sudo vim /etc/snmp/snmpd.conf
sudo /etc/init.d/snmpd restart
sudo yum install net-snmp
Edit community
sudo vim /etc/snmp/snmpd.conf
systemctl enable snmpd
sudo service snmpd restart
sudo umount /dev/sda1
sudo gdisk
/dev/sda
o
n
w
sudo mkfs.ext4 /dev/sda1
fsck -N /dev/sda1Check UID and GID of a user
id nova
Change UID of a user to 1420
usermod -u 1420 nova
Change GID of a group to 1420
groupmod -g 1420 nova
Replace file ownership old UID (1000) and old GID (1234) with the new one for both (1420)
find / -user 1000 -exec chown -h 1420 {} \;
find / -group 1000 -exec chgrp -h 1420 {} \;
Create new group and assign UID of 1420
groupadd -g 1420 nova
Make UID of media user be 1420
usermod -u 1420 media
Change current directory user/group recursively:
chown -R media:media .
If you truly want any user to have full permissions on a directory recursively
chmod -R a+rwx /mnt/downloads or chmod -R 777 /mnt/downloads
Create a new group and add auth user to the new media group
sudo groupadd media
sudo usermod -aG media auth or sudo adduser auth media
If you want to change the user owning this file or directory, you will have to use the command chown. For instance, if you run:
sudo chown username: myfolder
Then the user owning myfolder will be username. Then you can execute sudo chmod u+w myfolder to add the write permission for the user who owns the folder.
If you want to add this user to the group associated with "myfolder", you can run:
sudo usermod -a -G groupname username
...and then execute sudo chmod g+w myfolder to add the write permission to the group.
This sets permissions for specific users, without changing the ownership of the directory.
setfacl -m u:nova:rwx /etc/openvpn
user group global
rwx rwx rwx
current:
rwx --- ---
change to:
rw- r-- r--
what is changing:
user is losing execute
group is adding read
global is adding readsudo chmod -R u-x,g+r,a+r /my/path/
Disable firewall in Centos
systemctl disable firewalld
systemctl stop firewalld
Verify: systemctl status firewalld
Show all groups
cut -d: -f1 /etc/group
wrap lines
journalctl -xe --no-pager
Replaces spaces in the file names with periods
for file in *; do mv "$file" `echo $file | tr ' ' '.'` ; doneThis replaces homelab.city with will.mx
egrep -lRZ 'homelab.city' . | xargs -0 -l sed -i -e 's/homelab.city/will.mx/g
Find text in a file (source)
grep -rnw '/var/www/html/' -e 'punkwolf'