# Linux useful commands

#### memory

```
free -m

sar -a 2 2 

ps -eo pid,cmd,%mem,%cpu --sort=-%mem | head
```

#### CPU

```
sar -u 3 3

ps -eo pid,cmd,%mem,%cpu --sort=-%cpu | head

top
```

#### process

```
ps -e --forest | grep sshd

lsof -p pid
```

#### disk and files

```
df -hP

du -h 

ls -i

ls -ltr

state file

fuser filename

lsof filename
```

#### network

```
ss -altp | grep

nestat -altp | grep

fuser -v -k -n tcp 80

lsof -i :80

dig 


nslookup


grep tcp/80 /etc/services




iptable

```

#### accounts and permission

```
w

last

id userid

chage -l userid
chage -M -1 userid

chmod 775 file

chmod -R 775 folder

chwon root. file


history
```

#### system

```
init 6 
reboot

shutdown -h +10
shutdown -r now

halt 
poweroff -f
```

```
df -pH

fdisk -l 


free -mh

sar -u 2 2 

sar -



cpu

lsof  -i 80

lsof -p pid



fuser  -v 


ps aux | grep httpd

ps -eo pid,com,%mem,%cpu 

ps -e —forest

top

ss -altp

ls -i 

ls -ltr
```