Overview
This article is an introduction to some basic commands you will want to know while using SSH.
Requirements
This article assumes that:
- You are connected using your Server Administrator.
- You are connected using your primary SSH user. This is root or a sudo user.
- You are connected using your primary SSH user and have switched to root.
- You are connected using your primary SSH user. This is usually root or a sudo user.
- You are connected using your primary SSH user.
- You have used Terminal (Mac) or PuTTY (Windows) to log into the server.
STATEMENT OF SUPPORT
This article is provided as a courtesy. Installing, configuring, and troubleshooting third-party applications is outside the scope of support provided by (mt) Media Temple. Please take a moment to review the Statement of Support.
Linux folder structure
PLACEHOLDER NAMES
This article will be using the placeholder "00000", "example.com", and "file.html". Be sure to replace this with your actual site number, domain name, and file name.
Linux uses a nested folder structure to store different files. The top-level directory is considered the root directory, and is designated by /. Folders beneath the root level are separated by slashes.
When you first log into your server, you will be in your home directory:
/home/00000/users/.home/
And your website content is located in:
/home/00000/domains/example.com/
Move to another directory
Use this command to move into a directory:
cd
You can specify the full path from the root of the server:
cd /home/00000/domains/
You can type the path from where you are now (leave out the beginning /):
cd folder/
You can go up a directory level:
cd ..
You can return to your home directory:
cd ~
Linux folder structure
PLACEHOLDER NAMES
This article will be using the placeholder "user", "example.com", and "file.html". Be sure to replace this with your actual cPanel Login, domain name, and file name.
Linux uses a nested folder structure to store different files. The top-level directory is considered the root directory, and is designated by /. Folders beneath the root level are separated by slashes.
When you first log into your server, you will be in your home directory:
/home/user/
Your primary website content is located in:
/home/user/public_html/
Your add-on domain(s) content is located in:
/home/user/public_html/example.com
Move to another directory
Use this command to move into a directory:
cd
You can specify the full path from the root of the server:
cd /home/user/public_html/
You can type the path from where you are now (leave out the beginning /):
cd folder/
You can go up a directory level:
cd ..
You can return to your home directory:
cd ~
Linux folder structure
PLACEHOLDER NAMES
This article will be using the placeholder "user", "example.com", and "file.html". Be sure to replace this with your actual primary SSH/FTP user, domain name, and file name.
ROOT/SUDO ACCESS:
To access some folders you may need to use root or a sudo user.
Linux uses a nested folder structure to store different files. The top-level directory is considered the root directory, and is designated by /. Folders beneath the root level are separated by slashes.
When you first log into your server, you will be in your home directory:
/home/user/
Your website content is located in:
#Plesk
/home/var/www/vhosts/example.com/httpdocs/
#cPanel
/home/domainuser/public_html/
Move to another directory
Use this command to move into a directory:
cd
You can specify the full path from the root of the server:
cd /home/user/folder/
You can type the path from where you are now (leave out the beginning /):
cd folder/
You can go up a directory level:
cd ..
You can return to your home directory:
cd ~
Linux folder structure
PLACEHOLDER NAMES
This article will be using the placeholder "user", "example.com", and "file.html". Be sure to replace this with your actual primary SSH/FTP user, domain name, and file name.
Linux uses a nested folder structure to store different files. The top-level directory is considered the root directory, and is designated by /. Folders beneath the root level are separated by slashes.
When you first log into your server, you will be in your home directory:
/home/user/
Your website content is located in:
/home/user/html
Move to another directory
Use this command to move into a directory:
cd
You can specify the full path from the root of the server:
cd /home/user/folder/
You can type the path from where you are now (leave out the beginning /):
cd folder/
You can go up a directory level:
cd ..
You can return to your home directory:
cd ~
Where am I?
If you ever need to see exactly which folder you're in, use the following command:
pwd
What's in here?
To see a list of files and folders in our current directory:
ls -alh
ls is the list command, and -alh modifies the standard list in three ways. a means that all files, even hidden files, should be shown. l means that the long format is used - it shows things like file size and the date every file was last modified. h makes the sizes display in convenient units. Here's some sample output:
drwxr-xr-x 3 owner group 15 Oct 21 10:01 . drwxr-xr-x 6 owner group 6 Oct 21 09:13 .. -rw-r--r-- 1 owner group 137 Oct 21 10:01 .htaccess drwxr-xr-x 2 owner group 4 Jun 8 17:24 errors -rwxr-xr-x 1 owner group 379 Jan 28 2010 hello.pl -rw-r--r-- 1 owner group 45 Oct 30 2009 home.html -rw-r--r-- 1 owner group 83 Oct 21 09:47 file.html -rw-r--r-- 1 owner group 68 Jul 20 15:53 phpinfo.php
Linux file structure
Let's break down the elements of a file that are displayed when you run the ls -alh command from the previous section:
-rw-r--r-- 1 owner group 83 Oct 21 09:47 file.html
- -rw-r--r-- - These are the permissions for this file.
- r stands for read
- w stands for write
- x stands for execute
- The first character is standalone, and the next nine are in groups of three: the first triplet (rw-) applies to the owner, the second (r--) to the group, and the third (r--) to everyone. So, in this example, the owner has read and write access, the group just has read access, and everyone has read access. See File Permissions for an in-depth discussion.
- 1 - Number of links to this file.
- owner - Will show the owner of this file.
- group - Will show the group this file belongs to. May also be www-data.
- 83 - The size of this file.
- Oct 21 - The date this file was last modified.
- index.php - The name of this file.
Change permissions
This section shows basic commands for changing the permission settings on a file. It is highly recommended that you read File Permissions before making any changes, so you'll know what kinds of changes are good and what might be a security risk. Permissions can be changed using chmod, for example:
chmod 755 file.html
In the above example, 755 is a code which tells what kinds of read, write, and execute permissions you want for the file. The first number is for the owner, second for the group, and third for everyone.
Quick permissions guide:
7 = Read + Write + Execute
6 = Read + Write
5 = Read + Execute
4 = Read
3 = Write + Execute
2 = Write
1 = Execute
0 = All access denied
Change Owner/Group
Use chown to change the owner. Be sure to replace "ownername" with your actual owner:
chown ownername file.html
Use chgrp to change the group. Be sure to replace "groupname" with your actual group:
chgrp groupname file.html
To change the owner and group at once:
chown ownername:groupname file.html
Read file content
To look through a file, the quickest way to get all the contents on your screen is cat, for example:
cat file.html
If you have a large file, the amount of contents can be overwhelming. In that case, you have options to conveniently scroll through content. The less command lets you use the arrow keys to navigate through content, line by line. Press q to exit:
less file.html
The | more command allows you to press Enter to scroll down line by line. Press q to exit.
cat access_log | more
Search file content
To search a file for a specific phrase, use :
cat file.html | egrep "insertphrase"
This will list only the lines containing the phrase you've inserted. Be sure to include the quotation marks (").
Copy
Use the cp command to copy a file. Because we are creating a copy in the same location as the original, we will need to specify a new name in order to create our copy:
cp file.html file.html_copy
You can also copy a file to a new location. Be sure to replace "folder" with your actual folder path:
cp file.html folder/file.html
You can also copy an entire folder (along with all sub-folders using -R):
cp -R folder/ foldercopy
Move/Rename
Use mv to move a file to a new location. Be sure to replace "folder" with your actual folder path:
mv file.html folder/file.html
You can move an entire folder:
mv folder/ folder2
You can also rename a file using mv:
mv file.html
Create file
Create an empty file (which you can later open for editing) using touch:
touch file.html
CHECK PERMISSIONS:
Files are created with the owner and group of your SSH user. Once you've created a new file, it's a good idea to run ls -alh to make sure its ownership matches the rest of the files in the directory. If not, run the chown command from the earlier section.
Edit file
To edit a file use vi:
vi file.html
USING VI:
Press "i" to enter "insert mode" so you can type and copy/paste. Use the arrow keys to move back and forth in the file. Press "Esc" to exit "insert mode" when you are done modifying the file. Type ":wq" to save and quit. See Understanding basic vi (visual editor) for more details.
Delete file
WARNING
Before deleting a file, be EXTRA CAREFUL to ensure that you do not need the file, AND that you are deleting the correct file. If you are trying to disable a file or folder, we recommend simply renaming it.
To delete a file use rm:
rm file.html
You can recursively delete an entire folder and all its sub-folders using -rf but be VERY CAREFUL when using this command:
rm -rf folder
Zip/Unzip file
Use this command to compress a file. In this example, "folder.zip" is the name of the compressed file we wish to create, and "folder" is the name of the directory we wish to compress:
zip -r folder.zip folder
To decompress simply use:
unzip folder.zip
Disk use
You can view your total server disk usage by using:
df -h
To show all folder sizes for the current directory recursively, with their sizes. This may take time if you are in a high directory:
du -h
To show a disk use summary for the current directory. This may take time if you are in a high directory:
du -sh
An advanced find command you can run to find files over 10 MB. You can adjust the 10 MB variable to your needs:
find / -mount -noleaf -type f -size +10000k -print0 | xargs -0 ls -lhSr | awk '{printf "%*s %s\n",7,$5":",$9}'
Processes and System Services
To show current server proceses:
ps -auxf
To show processes and memory use live:
top
To start/stop/restart services. Replace "servicename" with your actual service:
service servicename start
service servicename stop
service servicename restart
Log Files
Log files can tell you a lot about what's happening on your server. Log files are generally very long, so you should use one of these commands to sort through them easily. Make sure to replace "/path/to/logs" with your actual file path.
To show the most recent 100 lines in a file:
tail -n 100 /path/to/logs
To watch the log files propogate live:
tail -f /path/to/logs
To see your SSH history use:
history
NOTE:
- For information on file paths, see System Paths and log file locations.
- It's normal to have hundreds of failed SSH and FTP connection attempts; it's a reminder that we all need to use strong passwords.
- Set up log rotation to keep logs from growing too large.
- The mail logs are great for seeing spam activity and for tracking message delivery/failure. See Troubleshooting common issues with email for further assistance.
Final tips
- When you are typing a path or file name, hit "Tab" after the first few letters. If it's the only file or folder matching the letters you've typed, the rest of it will auto-complete.
- Hit the up arrow to scroll back through previous commands - save yourself some typing!
- Always make a backup copy of the working version of a file before editing it.
- "q" or "CTRL+C" usually gets you out of any special mode you might be in.
- If you've encountered an unknown command, type "man" and then the command name to learn more about it. (Example: man ls) This will also show you special options like the -alh option for the list command.
