Helper Commands

Command line Helpers

Moving around

You move between folders with the cd command

cd /folder/ We will call folders directories or directory (dir) for short. You will find yourself remembering long old routes to places on a server

• cd /var/www/html/
• cd /var/log/apache2

Here are some handy shortcuts:

• cd ~/ Go to you logged in users home directory
• cd / Go to the root computer/server directory
• cd - Go to the last directory you were in
• cd ../ Go back a directory
• cd ../../ Go back two directories (and so on)
• cd . leaves you where you are

As a practical example depending on the server you may often need to find the location of error logs - depending on which web software the site is on there are different locations to look

• cd /var/logs/apache2 will put you in the apache server error log default directory
• cd /var/log/nginx will put you in the nigix server error log default directory

Searching Folders

Moving around is one thing but you still need to see whats in the folders

The ls command lists all files in a directory

ls
3         README.md one       two

ls -a List all files even hidden dot files

ls -a
.         ..        .git      .hidden   3         README.md one       two

You can end up with a quick display to help you find your way but sometimes you need more. To see the permissions of files and organise them in a list is really helpful

ls -l List of files with additional informaiton

ls -l
total 16
-rw-r--r--  1 jonathan.carter  staff     0 17 May 10:10 3
-rw-r--r--  1 jonathan.carter  staff  6784 15 May 16:22 README.md
-rw-r--r--  1 jonathan.carter  staff     0 17 May 10:10 one
-rw-r--r--  1 jonathan.carter  staff     0 17 May 10:10 two

ls -lh List of files with their size in human readable form

A small breakdown of each part permissions user user-group filesize date modified name

 ls -lh
total 16
-rw-r--r--  1 jonathan.carter  staff     0B 17 May 10:10 3
-rw-r--r--  1 jonathan.carter  staff   6.6K 15 May 16:22 README.md
-rw-r--r--  1 jonathan.carter  staff     0B 17 May 10:10 one
-rw-r--r--  1 jonathan.carter  staff     0B 17 May 10:10 two

This is the most common one I find myself using - combining all together

ls -lah

total 16
drwxr-xr-x   8 jonathan.carter  staff   256B 17 May 10:10 .
drwxr-xr-x  27 jonathan.carter  staff   864B 15 May 16:09 ..
drwxr-xr-x  12 jonathan.carter  staff   384B 17 May 10:14 .git
-rw-r--r--   1 jonathan.carter  staff     0B 17 May 10:10 .hidden
-rw-r--r--   1 jonathan.carter  staff     0B 17 May 10:10 3
-rw-r--r--   1 jonathan.carter  staff   7.8K 17 May 10:14 README.md
-rw-r--r--   1 jonathan.carter  staff     0B 17 May 10:10 one
-rw-r--r--   1 jonathan.carter  staff     0B 17 May 10:10 two

RTFM

As you go through you will hit many different commands and they will have multiple options - the only way for you to know the full extent of these is to read the manual. These generally open in vim so to exit type :q man ls man cd man man You can find alot of helpful information in these - if your command doesnt have one google it and see what you can find.

Often a command will also have a -h or --help command that will list its uses.

man --help
man, version 1.6c

usage: man [-adfhktwW] [section] [-M path] [-P pager] [-S list]
    [-m system] [-p string] name ...

  a : find all matching entries
  c : do not use cat file
  d : print gobs of debugging information
  D : as for -d, but also display the pages
  f : same as whatis(1)
  h : print this help message
  k : same as apropos(1)
  K : search for a string in all pages
  t : use troff to format pages for printing
  w : print location of man page(s) that would be displayed
      (if no name given: print directories that would be searched)
  W : as for -w, but display filenames only

  C file   : use `file' as configuration file
  M path   : set search path for manual pages to `path'
  P pager  : use program `pager' to display pages
  S list   : colon separated section list
  m system : search for alternate system's man pages
  p string : string tells which preprocessors to run
               e - [n]eqn(1)   p - pic(1)    t - tbl(1)
               g - grap(1)     r - refer(1)  v - vgrind(1)

Viewing and Editing Files

Now that you have found the folder you will need to read the file

cat filename Prints the files contents onto the terminal - this can dump alot of information if its a big file. You can also open the file in a text editor if you prefer

nano filename or nano error.log will open the file in a command line text editor nano. To exit ctrl x and type y will save your changes ctrl c will exit out of the file without saving your changes - this is also a pretty useful way to back out of a program in the cli.

Most terminals will have multiple text editors you can use - nano vim are common and popular.

Vim/Vi is a bit different to other editors to exit you have to type :q

Suspend and re-open

ctrl z will suspend the current program - handy for a text editor you want to check something but dont want to save the file Once your done running fg or foreground command will put you back into the file.

Handy Logging

If you are faced with a very large log file sometimes it helps to check the last few lines of the file.

tail -f error.log

Is a really handy command that will open the error log file and print to the screen whatever gets appended to it.

This can be useful on a site that is broken broken as it can often store useful debug information. You can reload the broken page and see the logs realtime. You can also dump the specified number of lines if you just want to see for example the last 100 lines.

tail -100 error.log

For the record - theres also the opposite command head to see the top few lines of a file. (if you ever need it)

Appending and Amending Files

Sometimes you can work with files that can be giant - gb's of size. Tail is great for the last few bits what can also be helpful is sending data from one command to another

tail -100 error.log > last100lines.log

This would write the results of your tail command into a new file overwriting the file

tail -100 error.log >> last100lines.log

This would ammend the file at the bottom

History help

Sometimes you need to find a command you ran previously because your memory isnt all it used to be - it happens no one is perfect. The history command will display all commands previously run on your system by your user.

A really helpful trick is to press the up arrow on your keyboard, as this will loop through the last commands. If you remember doing a command in the mists of time and kind of remember some of it you can pass the command into another helpful function grep

history | grep searchterm

As an example -

history | grep git normally tells me what the damn command was I ran to reset my git branch to a new org

 9739  git remote -v
 9740  git remote set-url  origin [email protected]:dividohq/finance-plugin-woocommerce.git
 9741  git status

Grep for quick searching

If you dont have a fancy IDE for your coding sometimes you will need to find a bunch of random stuff in a folder. grep can help you here too

grep -Ril woocommerce_product_write_panel_tabs ../demo_divido_co/ This command will recursively search for files with woocommerce_product_write_panel_tabs in in the ../demo_divido_co/ folder. It will dump out all files with that string in - which can help.

A note on permissions

Who you are on the server matters - if you are logged in as root you are going to endup running a command and breaking a websites permissions Especially if you are running some magento commands - you can recursively reset the file owner like so:

chown -R www-data:www-data ../m2dev

This command changes the owner of files in the m2dev dir to be owned by the default apache web user www-data.

chmod 777 file

If you are getting weird permissions this means everyone can do anything to it. You wouldnt leave your car open, with the keys in,engine running, with your pin number taped to you credit card and id docs in a high crime area so dont leave your files lucky 7 on a server. If you turn your files lucky to fix an issue always put them back when your done.

Mysql Helpers

You can login with mysql on the server - obviously there are security implications to this so think about it. mysql -u root -p

root@server:~# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 32681
Server version: 5.7.26-0ubuntu0.16.04.1 (Ubuntu)

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

Once you have a mysql shell you can exit it mysql> exit;

Some basic example commands: mysql> SELECT * FROM table LIMIT 5 mysql> UPDATE wp_options SET value='this' WHERE id='that'

Logging in automatically without -p

create a empty file touch ~/.mylogin.cnf

user = root
password = super-secure-password

Make sure you restrict access to this file! chmod 600 /home/example_user/.mylogin.cnf

BACKUP and RESTORE

Make a full backup of all DB's

mysqldump --all-databases --single-transaction --quick --lock-tables=false > full-backup-$(date +%F).sql -u root -p

Make a backup of a single DB

mysqldump -u username -p db1 --single-transaction --quick --lock-tables=false > db1-backup-$(date +%F).sql

Make a backup of a single Table from a DB

mysqldump -u username -p --single-transaction --quick --lock-tables=false db1 table1 > db1-table1-$(date +%F).sql

Create an automated backup on a server

crontab -e 0 1 * * * /usr/bin/mysqldump --defaults-extra-file=/home/example_user/.my.cnf -u root --single-transaction --quick --lock-tables=false --all-databases > full-backup-$(date +\%F).sql

Restore from our backup

mysql -u root -p < full-backup.sql

Test