Supercomputing for Beginners: Discussion

Frequently Asked Questions

Transferring files interactively with sftp

scp is useful, but what if we don’t know the exact location of what we want to transfer? Or perhaps we’re simply not sure which files we want to transfer yet. sftp is an interactive way of downloading and uploading files. Let’s connect to a cluster, using sftp- you’ll notice it works the same way as SSH:

sftp yourUsername@remote.computer.address

This will start what appears to be a bash shell (though our prompt says sftp>). However we only have access to a limited number of commands. We can see which commands are available with help:

sftp> help

Available commands:
bye                                Quit sftp
cd path                            Change remote directory to 'path'
chgrp grp path                     Change group of file 'path' to 'grp'
chmod mode path                    Change permissions of file 'path' to 'mode'
chown own path                     Change owner of file 'path' to 'own'
df [-hi] [path]                    Display statistics for current directory or
                                   filesystem containing 'path'
exit                               Quit sftp
get [-afPpRr] remote [local]       Download file
reget [-fPpRr] remote [local]      Resume download file
reput [-fPpRr] [local] remote      Resume upload file
help                               Display this help text
lcd path                           Change local directory to 'path'
lls [ls-options [path]]            Display local directory listing
lmkdir path                        Create local directory
ln [-s] oldpath newpath            Link remote file (-s for symlink)
lpwd                               Print local working directory
ls [-1afhlnrSt] [path]             Display remote directory listing

# omitted further output for clarity

Notice the presence of multiple commands that make mention of local and remote. We are actually connected to two computers at once (with two working directories!).

To show our remote working directory:

sftp> pwd

Remote working directory: /global/home/yourUsername

To show our local working directory, we add an l in front of the command:

sftp> lpwd

Local working directory: /home/jeff/Documents/teaching/hpc-intro

The same pattern follows for all other commands:

ls shows the contents of our remote directory, while lls shows our local directory contents.
cd changes the remote directory, lcd changes the local one.

To upload a file, we type put some-file.txt (tab-completion works here).

sftp> put config.toml

Uploading config.toml to /global/home/yourUsername/config.toml
config.toml                                   100%  713     2.4KB/s   00:00 

To download a file we type get some-file.txt:

sftp> get config.toml

Fetching /global/home/yourUsername/config.toml to config.toml
/global/home/yourUsername/config.toml                               100%  713     9.3KB/s   00:00

And we can recursively put/get files by just adding -r. Note that the directory needs to be present beforehand.

sftp> mkdir content
sftp> put -r content/

Uploading content/ to /global/home/yourUsername/content
Entering content/
content/scheduler.md              100%   11KB  21.4KB/s   00:00
content/index.md                  100% 1051     7.2KB/s   00:00
content/transferring-files.md     100% 6117    36.6KB/s   00:00
content/.transferring-files.md.sw 100%   24KB  28.4KB/s   00:00
content/cluster.md                100% 5542    35.0KB/s   00:00
content/modules.md                100%   17KB 158.0KB/s   00:00
content/resources.md              100% 1115    29.9KB/s   00:00

To quit, we type exit or bye.