Various helpful command line commands

System

Check whether a reboot is required:

ls /var/run/reboot-required

In a bash script, you can use:

#!/bin/bash
if [ -f /var/run/reboot-required ]; then
  echo 'reboot required'
fi

Copy files between servers

Copy between servers with user privileges

$ rsync -avz -e 'ssh -p 22' dir user@x.x.x.x:/path/to/dir/

Copy between servers with root privileges
```
$ rsync -avz -e 'ssh -p 22 -i /home/user/.ssh/id_ecdsa' --rsync-path="sudo rsync" dir user@x.x.x.x:/path/to/dir/
```
- also enable the user on the target machine to run rsync with root privileges, to do so create file /etc/sudoers.d/rsync (line 1) with content (line 2)
```
$ sudo visudo /etc/sudoers.d/rsync
user ALL = NOPASSWD:/usr/bin/rsync
```

Copy from cloud

$ rsync -avz -e 'ssh -p 22 -i /path/to/identity/file' --info=progress2 user@x.x.x.x:/path/to/dir/ /local/dir/

File Management

Copy all files except some in all sub directories

cd ~/movies
find . -type d -exec mkdir ~/copied/{} \;
find . -type f -not -name *.mkv -exec cp {} ~/copied/{} \;

Modify file but preserve modified timestamp

cp -p <file> <file-with-timestamp>
vim <file>
touch -r <file-with-timestamp> <file>

Find all files containing specific text

Since you have GNU find/xargs, this is a safe way for xargs to read filenames:
```
find . -type f -print0 | xargs -0 grep "some string"
```
If you only want the filenames that have a matching line without showing the matching line:
```
find . -type f -print0 | xargs -0 grep -l "some string"
```

Find all files which were modified within the last month from the current directory

find . -newermt $(date +%Y-%m-%d -d '1 month ago') -type f -print

Find all files modified on the 7th of June, 2006

find . -type f -newermt 2007-06-07 ! -newermt 2007-06-08

Find all files accessed on the 29th of september, 2008

find . -type f -newerat 2008-09-29 ! -newerat 2008-09-30

Find files which had their permission changed on the same day

find . -type f -newerct 2008-09-29 ! -newerct 2008-09-30

Copy all files excluding hardlinks

rsync -aAXv /origin /dest
rsync -azAX -H --delete --numeric-ids /path/to/source /path/to/dest

Determine size of a folder path

du -hs

Change permissions for all files in a directory tree

find -type f -print0 | xargs -0 chmod 644

Copy all files

rsync -av <source> <dest>

Count all files in a directory (without .files)

ls -1 | wc -l

Change the name of all files like "source_1111_22.jpg" to "dest_1111_22.jpg"

rename 's/source_(\d{4}_\d{2})\.jpg$/dest_$1.jpg/' *

If “source” is “sourca” and “sourcb”, do the following:

rename 's/\w{6}_(\d{4}_\d{2})\.jpg$/dest_$1.jpg/' *

Delete Directory and Files within recursively

find -type d -name <dir> -exec rm -rf {} \;

Refresh display of the last 15 lines of a file every 2 seconds

watch tail -n 15 file.name

Zip folder

zip -r myarchive.zip dir1 -x dir1/ignoreDir1/**\* dir1/ignoreDir2/**\*

Linux rename command

Zip including hidden files

zip -r archive.zip * .[^.]*

Zip including hidden files

Disk Management

# iotop
smartctl -H /dev/sda
blkid /dev/sda1
mount -t cifs -o user=luke //192.168.1.104/share /mnt/linky_share
mdadm --manage /dev/md0 --add /dev/sdb1

Diskspace information:

df -h

VirtualBox

usermod -a -G groupName userName

Add physical disk:

VBoxManage internalcommands createrawvmdk -filename /home/bco/.VirtualBox/diskname.vmdk -rawdisk /dev/sda

Vim

Find each occurrence of 'foo' (in all lines), and replace it with 'bar'.:

:%s/foo/bar/g

Find each occurrence of 'foo' (in the current line only), and replace it with 'bar':

:s/foo/bar/g

Search and Replace

vi

To fix the broken arrow keys in insert mode in vi, change the vi default config as follows:

$ vi ~/.exrc
set nocompatible

Settings

hostname <newname>
vim /etc/hostname
vim /etc/hosts

vim /usr/share/X11/xorg.conf.d/00-Settings.conf
Section"ServerFlags"
Option "BlankTime" "600"
EndSection

Port scan

TCP Port Scan with Nmap

check for root privileges

Don't forget to change the root password. If any user has UID 0 besides root, they shouldn't. Bad idea. To check:

grep 'x:0:' /etc/passwd

Again, you shouldn't do this but to check if the user is a member of the root group:

grep root /etc/group

To see if anyone can execute commands as root, check sudoers:

cat /etc/sudoers

To check for SUID bit, which allows programs to be executed with root privileges:

find / -perm -04000

Add a service to the init system

Write a script with the LSB tags to be read by the insserv service:

#!/bin/sh
### BEGIN INIT INFO
# Provides: myservice
# Required-Start: sshd
# Required-Stop: sshd
# Should-Start:
# Should-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start myservice
# Description: Start myservice after sshd is started (example)
### END INIT INFO
myservice -options
exit 0

Name the script myservice, move it to /etc/init.d/, and run the following command as root:

# update.rc-d myservice defaults

Table of Contents

Various helpful command line commands

System

Copy files between servers

File Management

Copy all files except some in all sub directories

Modify file but preserve modified timestamp

Find all files containing specific text

Find all files which were modified within the last month from the current directory

Find all files modified on the 7th of June, 2006

Find all files accessed on the 29th of september, 2008

Find files which had their permission changed on the same day

Copy all files excluding hardlinks

Determine size of a folder path

Change permissions for all files in a directory tree

Copy all files

Count all files in a directory (without .files)

Change the name of all files like "source_1111_22.jpg" to "dest_1111_22.jpg"

Delete Directory and Files within recursively

Refresh display of the last 15 lines of a file every 2 seconds

Zip folder

Zip including hidden files

Disk Management

VirtualBox

Vim

vi

Settings

Port scan

check for root privileges

Add a service to the init system

Know How