Linux

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Linux commands

Starting and Stopping httpd

https://docs.fedoraproject.org/en-US/Fedora/12/html/Deployment_Guide/s1-apache-startstop.html

  • To start the server using the apachectl control script as root type:
 apachectl start
  • To stop the server, as root type:
 apachectl stop
  • You can restart the server as root by typing:
 apachectl restart or: /sbin/service httpd restart
  • You can also display the status of your httpd server by typing:
 apachectl status

unzip tar.gz file

tar -xvzf community_images.tar.gz

To explain a little further, tar collected all the files into one package, community_images.tar. The gzip program applied compression, hence the gz extension. So the command does a couple things: 

   f: this must be the last flag of the command, and the tar file must be immediately after. It tells tar the name and path of the compressed file.
   z: tells tar to decompress the archive using gzip
   x: tar can collect files or extract them. x does the latter.
   v: makes tar talk a lot. Verbose output shows you all the files being extracted.

VNC Server

How to Setup VNC Server

Step 1: Install Required Packages For CentOS/RHEL 6: 

# yum groupinstall "Desktop"

For CentOS/RHEL 5: 

# yum groupinstall "GNOME Desktop Environment"

# yum install pixman pixman-devel libXfont

Step 2: Install VNC Server 

# yum install vnc-server

Step 3: Connect VNC Server using VNC Viewer

vncserver - start or stop a VNC server

Synopsis 

 vncserver [:display#] [-name desktop-name] [-geometry widthxheight] [-depth depth] [-pixelformat format] [-fp font-path] [-fg] [-autokill] [Xvnc-options...]
 vncserver -kill :display#
 vncserver −list

vncpasswd - change the VNC password

Synopsis 

vncpasswd [passwd-file]
vncpasswd -f 

$ vncpasswd 
Password:
Verify:

Docker commands

ssh root@devops


https://docs.docker.com/engine/reference/commandline/exec/ 

docker exec -it dockername bash
cd /root/so
docker exec -it dockername bash
docker exec -it --user=root devdb bash

https://docs.docker.com/engine/reference/commandline/logs/ 

docker logs -f dockername

docker restart dockername

show all dockers 

docker ps
docker ps -a (Show all containers)

Recover dump file in docker 

sftp://devdb.webbfontaine.am/home/user //Put your dmp files here

minioclient cp wfs3/bhqa/twm/db/1538024414.dmp dump.dmp

sudo su
docker cp backup/dump.dmp devdb:/dump.dmp
docker exec -it --user=root devdb  bash 
OR
docker exec -it --user=0 devdb  bash 

ON ERROR
OCI runtime exec failed: exec failed: container_linux.go:348: starting container process caused "chdir to cwd (\"/home/oracle\") set in config.json failed: permission denied": unknown

docker exec --interactive --tty --user root --workdir / dockername  bash

cd /
mv /backup.dmp opt/oracle/admin/YOUR_SID/dpdump/
cd opt/oracle/admin/YOUR_SID/
chown -R dockername dpdump/


show all UID 

[root@52c17fb398f9]# awk -F: '{printf "%s:%s\n",$1,$3}' /etc/passwd
root:0
bin:1
daemon:2
adm:3
lp:4
sync:5
shutdown:6
halt:7
mail:8
operator:11
games:12
ftp:14
nobody:99
systemd-bus-proxy:999
systemd-network:192
dbus:81
sshd:74
oracle:1000
rpc:32
rpcuser:29
nfsnobody:65534

Midnight Commander

http://klimer.eu/2015/05/01/use-midnight-commander-like-a-pro/

create file 

  Shift + F4 - Create a new file

Selecting files 

   Insert (Ctrl + t alternatively) - select files (for example, for copying, moving or deleting).
   + - select files based on a pattern.
   \ -unselect files based on a pattern.
   * - reverse selection. If nothing was selected, all files will get selected.

Accessing the shell 

  Alt + Enter - copy the currently selected file’s name to the shell.

Panels 

  Alt + t - switch the panel’s listing mode in a loop: default, brief, long, user-defined. “long” is especially useful, because it maximises one panel so that it takes full width of the window and longer filenames fit on screen.
  Alt + i - synchronize the active panel with the other panel. That is, show the current directory in the other panel.
  Ctrl + u - swap panels.
  Alt + y - move to the previous directory in history.
  Alt + u - move to the next directory in history.

Searching files 

  Alt + ? - shows the full Find dialog.
  Alt + s or Ctrl + s - quick search mode. Start typing and the selection will move to the first matching file. Press the shortcut again to jump to another match. Use wildcards (*, ?) for easier matching.

Common actions 

  Ctrl + Space - calculate the size of the selected directories. Press this shortcut when the selection is on .. to calculate the size of all the directories in the current directory.
  Ctrl + x s (that is press Ctrl + x, let it go and then press s) - create a symbolic link (change s to l for a hardlink). I find it very useful and intuitive - the link will, of course, be created in the other panel. You can change it’s destination and name, like with any other file operation.
  Ctrl + x c - open the chmod dialog.
  Ctrl + x o - open the chown dialog.

Bonus assignments 

  Compare directories (Ctrl + x d)

SSH connection problem with “Host key verification failed…” error "Host key verification failed" means that the host key of the remote host was changed.

Ssh stores the host keys of the remote hosts in ~/.ssh/known_hosts. You can either edit that text file manually and remove the old key (you can see the line number in the error message), or use 

ssh-keygen -R hostname

Working with CSV

Repeat a Linux Command Every X Seconds

 while true; do wc -l SAD_SEL_TRACK_DATA_TABLE.csv ; sleep 5; done

Get only the first row using head command:

 $ head -1 myfile.csv
 1,2,3,4,5

Get the count of lines in a csv file

1) wc -l filename.csv
2) cat DATA_TABLE.csv  | wc -l
3) awk '{n+=1} END {print n}' DATA_TABLE.csv

the following command  will print all of the lines of the file DATA_TABLE.csv that begin with a # character:
grep -v "#" DATA_TABLE.csv | wc -l

Remove particular symbol from CSV

this remove " from TABLE.csv and create new file TABLE2.csv 

 sed 's/\"//g' TABLE.csv > TABLE2.csv

Where can I find the Java SDK in Linux?

This depends a bit from your package system ... if the java command works, you can type readlink -f $(which java) to find the location of the java command

Copy all files from remote server exclude excel files

rsync -av -e ssh --exclude='*.xls' --exclude='*.xlsx' remoteuser@remotehost:/from_folder /to_folder

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