Introduction to scp command
scp is a command-line tool in Linux to copy files between hosts on a network. It allows you to copy files and directories without logging into the remote hosts. It uses ssh connection and security to transfer data securely over the network. Unlike rcp, scp will ask for passwords if needed for authentication.
How scp command works (syntax)
The scp connects to the ssh server and executes the command. The scp exits 0 on success, and >0 if an error occurs. The basic syntax of scp command is:
$ scp [option] {files|directories} user1@destination_host1:directory1/filename1 [user2@destination_host2:directory2/filename2] ..
scp can be used to transfer files and directories securely from one Linux to another Linux server. You can also copy the same file and directory to more than one hosts.
Replace [option] with supported list of options which we will cover throughout this cheat sheet tutorial:
Replace {files|directories} with the file(s) or/and directory which you intend to copy to remote or source host
The destination to which the source file will be copied is defined by user1@destination_host1:directory1/filename1. You can add more than one hosts to copy files and directories to more than one destination host
user1is the account of the destination Linux server using which SSH will be performeddestination_host1is the hostname of the destination computer.directory1is the directory name under which the source file will be copied. If not dpecified then the file will be copied to the home directory of the user used to do SSH. For example, here user1's home directory would be used if destination is not specified.filename1is the name of source file which will be copied. Now ideally we don't specify filename in which case, the filename of the source would be used on destination. We specify the filename mostly when we want to copy the file as a different name on destination host.
If the source file already exists in the destination computer, scp will replace the contents of the destination file with the source file (keeping the inode). If the destination file does not exist yet, an empty file with destination filename is created and the contents of the source file are added to it.
Different examples to use scp command
As we have gone through the detail of scp, now let's see the practical examples of scp command in Linux hosts.
1. scp command to copy a file from local to remote host
You can use the following command to copy a file from a local host to a remote host.
$ scp source_filename user@destination_host:/destination_folder
Sample Output:
deepak@golinux:~$ scp test_file root@10.0.2.15:/snap
root@10.0.2.15's password:
test_file 100% 28 0.0KB/s 00:00
2. scp command to copy a file from remote to local host
To copy a file from a remote host to a local host, you can use the following command.
$ scp user@remote_host:/remote_directory/filename /local_directory
Sample Output:
deepak@golinux:~$ scp sam@10.0.2.15:test/test_file /home/deepak/Documents sam@10.0.2.15's password: test_file 100% 28 0.0KB/s 00:00 deepak@golinux:~$ ls Documents test_file
3. Transfer files between two remote hosts with scp command
You can copy a file from one remote host to another remote host using -3 option with scp command. Without this option the data is copied directly between the two remote hosts.
$ scp -3 user1@source_host:directory1/filename1 user2@destination_host:directory/filename
In this example we will copy /tmp/file1 from server-1 to server-2 using client host.
[root@server-1 ~]# touch /tmp/file1 [root@server-1 ~]# ls -l /tmp/file1 -rw-r--r-- 1 root root 0 Oct 3 18:25 /tmp/file1
Next we will connect to client host and copy /tmp/file1 from server-1 to server-2:
deepak@client:~$ scp -3 root@server-1:/tmp/file1 root@server-2:/tmp/ root@server-2's password: root@server-1's password: Passw0rd
Verify the file on server-2:
[root@server-2 ~]# ls -l /tmp/file1
-rw-r--r-- 1 root root 0 Oct 3 18:29 /tmp/file1
The file is successfully copied, but as you can see that the scp command prompts for password of both the host at the same time wherein the password of one of the destination host is not visible on the console but while providing the password of second destination host, the password is visible in plain text format on the console.
So scp may not be the best to tool transfer files from one remote host to another remote host.
4. scp command to copy files and directories recursively
-r option allows you to copy an entire directory recursively. All the files and sub-directories present in that directory will be copied.
$ scp -r source_dir_name user@destination_host:destination_folder
Sample Output:
deepak@golinux:~$ scp -r Folder sam@10.0.2.15:/home/sam
sam@10.0.2.15's password:
hello.c 100% 31 0.0KB/s 00:00
file.txt 100% 47 0.1KB/s 00:00
doc1 100% 86 0.1KB/s 00:00
deepak@golinux:~$ ls -l /home/sam/Folder
total 16
-rw-rw-r-- 1 sam sam 86 Sep 30 19:58 doc1
-rw-rw-r-- 1 sam sam 47 Sep 30 19:58 file.txt
drwxrwxr-x 2 sam sam 4096 Sep 30 19:57 folder2
-rw-rw-r-- 1 sam sam 31 Sep 30 19:58 hello.c
5. Display verbose output for scp command
With the help of -v option, you can view the detailed information of scp process in the background. It prints the debug information which can help to debug connection, authentication, and configuration problems.
$ scp -v source_filename user@destination_host:destination_folder
Sample Output:
deepak@golinux:~$ scp -v test_file sam@10.0.2.15:/home/sam/test Executing: program /usr/bin/ssh host 10.0.2.15, user sam, command scp -v -t /home/sam/test OpenSSH_7.2p2 Ubuntu-4ubuntu2.10, OpenSSL 1.0.2g 1 Mar 2016 debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 19: Applying options for * debug1: Connecting to 10.0.2.15 [10.0.2.15] port 22. debug1: Connection established. ..... Sending file modes: C0664 28 test_file Sink: C0664 28 test_file test_file 100% 28 0.0KB/s 00:00 debug1: client_input_channel_req: channel 0 rtype exit-status reply 0 debug1: channel 0: free: client-session, nchannels 1 debug1: fd 0 clearing O_NONBLOCK debug1: fd 1 clearing O_NONBLOCK Transferred: sent 2744, received 2616 bytes, in 1.2 seconds Bytes per second: sent 2376.9, received 2266.0 debug1: Exit status 0
6. Enable compression with scp command
Use -C option to enable the compression while performing file transfer. It does not compress the file types like .zip, .rar, .iso, .jpg, .png, etc.
NOTE: File transfer may take longer when compression is enabled
$ scp -C source_filename user@destination_host:destination_folder
Here, I have a file of 35MB in size:
deepak@ubuntu:~$ ls -lSh /tmp/file1
-rw-rw-r-- 1 deepak deepak 35M Oct 3 18:39 /tmp/file1
First we attempt to transfer the file without any compression which took around 2 seconds:
deepak@ubuntu:~$ scp /tmp/file1 root@server-2:/tmp/
root@server-2's password:
file1 100% 34MB 16.4MB/s 00:02
Next we enable compression and then perform transfer which took around 5 seconds:
deepak@ubuntu:~$ time scp -C /tmp/file1 root@server-2:/tmp/ root@server-2's password: file1 100% 34MB 6.4MB/s 00:05
So, the file transfer took comparatively longer when compression is enabled with scp command.
7. Limit the bandwidth in transfer with scp command
You can use -l option to limit the used bandwidth while copying. The bandwidth is specified in Kbits/s.
$ scp -l bandwidth_num source_filename user@destination_host:destination_folder
Sample Output:
deepak@golinux:~$ scp -l 5 iotop_0.6-1_i386.deb root@10.0.2.15:/var root@10.0.2.15's password: iotop_0.6-1_i386.deb 100% 23KB 2.1KB/s 00:11
8. scp command to preserve modification times, access times, and modes from original file
If you want to keep modification times, access times, and modes same as the original file to the copy file, you can use -p option like below.
$ scp -p source_filename user@destination_host:destination_folder
Sample Output:
9. Specify the port to connect using scp command
You can use -P option to specify the port to connect. The default port is 22 but if your SSH server is running on a different port then you can use -P <port> to specify an alternate port to perform the transfer.
$ scp -P port_num source_filename user@destination_host:destination_folder
For example, if SSH is using port 3022 on destination host then you can use scp with -P 3022 to perform the transfer.
deepak@golinux:~$ scp -P 3022 test_file sam@10.0.2.15:/home/sam/test
10. Enable quiet mode with scp command
Using -q option hides the progress meter while copying files. It also suppresses the warning and diagnostic messages from ssh.
$ scp -q source_filename user@destination_host:destination_folder
Sample Output:
deepak@golinux:~$ scp -q test_file sam@10.0.2.15:/home/sam/test
sam@10.0.2.15's password:
deepak@golinux:~$
11. Force scp to use IPv6 address only
-6 option forces the scp to use IPv6 address only. Other addresses are not supported with this command.
$ scp -6 source_filename user@destination_host:destination_folder
Sample Output:
deepak@golinux:~$ scp -6 test_file sam@10.0.2.15:/home/sam/test
Similarly, you can use -4 to force scp to use IPv4 address only. By default Ipv4 address is used.
$ scp -4 source_filename user@destination_host:destination_folder
12. Force scp to use protocol version
Use -1 option to force scp to use protocol version 1.
$ scp -1 source_filename user@destination_host:destination_folder
Sample Output:
deepak@golinux:~$ scp -1 test_file root@10.0.2.15:/snap
-2 option forces scp to use protocol version 2.
deepak@golinux:~$ scp -2 test_file root@10.0.2.15:/snap
root@10.0.2.15's password:
test_file 100% 28 0.0KB/s 00:00
13. Prevent asking for passwords with scp command
To prevent scp asking for passwords, you can use -B option. You may not gain access to the server without authentication. This can be a preferred method when you have setup passwordless SSH authentication.
$ scp -B source_filename user@destination_host:destination_folder
For Example, here I have setup passwordless authentication between server-1 and server-2 for deepak user. So I can use -B to perform the file transfer without any password prompt:
deepak@server-1:~$ scp -B /tmp/file1 deepak@server-2:/tmp/
file1 100% 34MB 35.0MB/s 00:00
But if the provided user requires password to login to the remote host, in such case this command will fail as shown below:
deepak@server-1:~$ scp -B /tmp/file1 deepak@server-2:/tmp/
deepak@server-2: Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
lost connection
14. Use identity file to transfer with scp command
An identity file contains a private key that can be used in SSH to have access to the server. You can create an identity file using ssh-keygen command. To select the identity file(.pem) for public-key authentication, you can use -i option.
$ scp -i identity_file source_filename user@destination_host:destination_folder
Sample Output:
deepak@golinux:~$ scp -i key.pem test_file sam@10.0.2.15:/home/sam/test
sam@10.0.2.15's password:
test_file 100% 28 0.0KB/s 00:00
15. Specify ssh configuration file with scp command
-F option allows you to specify the ssh configuration file for ssh. This option is directly passed to ssh. I have already written a detailed article to learn more about ssh_config file. I hope you know ssh_config is different compared to sshd_config where the former is the client config file while latter is server config file.
$ scp -F ssh_config source_filename user@destination_host:destination_folder
For Example, I try to connect to server-2 here and the connection timed out because I have not configured my /etc/hosts to identify server-2 host.
deepak@server-2:~$ scp -o ConnectTimeout=1 /tmp/file1 server-2:/tmp/
ssh: connect to host server1 port 22: Connection timed out
lost connection
Now, let me create a new /tmp/ssh_config file (I will not use the default one for this example) with following values:
$ cat /tmp/ssh_config Host server-2 HostName=192.168.0.165 StrictHostKeyChecking=no User=root PasswordAuthentication=yes GSSAPIAuthentication=no ConnectTimeout=10
Here, I have defined the IP of server-2 and some other SSH options which must be used whenever I try to connect to server-2:
deepak@server-2:~$ scp -F /tmp/ssh_config /tmp/file1 server-2:/tmp/
root@192.168.0.165's password:
file1 100% 34MB 44.7MB/s 00:00
16. scp command to select ciphers for encrypting the data transfer
-c option lets you select the ciphers for encrypting the data transfer.
$ scp -c cipher_name source_filename user@destination_host:destination_folder
Sample Output:
deepak@golinux:~$ scp -c blowfish-cbc test_file sam@10.0.2.15:/home/sam sam@10.0.2.15's password: test_file 100% 28 0.0KB/s 00:00
To view this list of ciphers, use the following command:
deepak@golinux:~$ ssh -Q cipher 3des-cbc blowfish-cbc cast128-cbc arcfour arcfour128 arcfour256 aes128-cbc aes192-cbc aes256-cbc rijndael-cbc@lysator.liu.se aes128-ctr aes192-ctr aes256-ctr aes128-gcm@openssh.com aes256-gcm@openssh.com chacha20-poly1305@openssh.com
17. Pass additional options to ssh using scp command
You can use -o option to pass options to ssh in the format used ssh_config. It is useful for specifying options for which scp does not have the separate command-line flag.
$ scp -o option=value source_filename user@destination_host:destination_folder
Following are some of the available options that can be used with above -o command.
AddKeysToAgent AddressFamily BatchMode BindAddress CanonicalDomains CanonicalizeFallbackLocal CanonicalizeHostname CanonicalizeMaxDots CanonicalizePermittedCNAMEs CertificateFile ChallengeResponseAuthentication CheckHostIP Ciphers ClearAllForwardings ... StrictHostKeyChecking TCPKeepAlive Tunnel TunnelDevice UpdateHostKeys UsePrivilegedPort User UserKnownHostsFile VerifyHostKeyDNS VisualHostKey XAuthLocation
Here, I have give a couple of examples to use -o with scp command. Enable StrictHostKeyChecking while performing the transfer:
deepak@server-1:~$ scp -o StrictHostKeyChecking=no /tmp/ssh_config /tmp/file1 server-2:/tmp/
ssh_config 100% 158 194.3KB/s 00:00
file1 100% 34MB 38.7MB/s 00:00
Provide ConnectTimeout and disable StrictHostKeyChecking while performing the file transfer with scp command:
deepak@server-1:~$ scp -o ConnectTimeout=10 -o StrictHostKeyChecking=no /tmp/ssh_config /tmp/file1 server-2:/tmp/ ssh_config 100% 158 125.6KB/s 00:00 file1 100% 34MB 40.2MB/s 00:00
Enable PasswordAuthentication while performing the file transfer:
deepak@server-1:~$ scp -o PasswordAuthentication=yes /tmp/ssh_config /tmp/file1 server-2:/tmp/ ssh_config 100% 158 87.4KB/s 00:00 file1 100% 34MB 29.5MB/s 00:01
Enable BatchMode while performing the file transfer:
deepak@server-1:~$ scp -o BatchMode=yes /tmp/ssh_config /tmp/file1 server-2:/tmp/ ssh_config 100% 158 17.4KB/s 00:00 file1 100% 34MB 36.8MB/s 00:00
Conclusion
In this article, you have learned about scp and its commands to copy files between hosts. It is a secure and useful remote file copy program. We hope you will be now able to copy files using scp command. If you have any confusion, please don't hesitate to ask in the comment section.
What's Next
15+ SSH command examples in Linux [Cheat Sheet]
Further Reading
