Exercise: Move files between machines

Move files between machines

• Write a Host block in ~/.ssh/config.
• Upload and download with scp and sftp.
• Mirror a directory with rsync and preview with -n.

Start the exercise

On workstation, start the exercise. It creates the account ops on servera and the key ~/.ssh/id_ops on workstation, installed for ops (the result of the previous exercise).

[student@workstation ~]$ lab start sa-transfer

Later tasks assume that you are logged in to the server they name: ssh student@servera from workstation, then sudo -i for a root shell.

Prepare files and an alias

This exercise needs the key from the previous exercise (~/.ssh/id_ops, installed for ops@servera). Create a working directory ~/sshlab with inventory.txt (any line) and reports/a.txt, reports/b.txt. Then add a Host opsa block to ~/.ssh/config and test it.

[student@workstation ~]$ mkdir -p ~/sshlab/reports && cd ~/sshlab
[student@workstation sshlab]$ echo "web1 10.0.0.11" > inventory.txt
[student@workstation sshlab]$ echo r1 > reports/a.txt; echo r2 > reports/b.txt
[student@workstation sshlab]$ cat >> ~/.ssh/config <<'EOT'

Host opsa
    HostName servera
    User ops
    IdentityFile ~/.ssh/id_ops
    IdentitiesOnly yes
EOT
[student@workstation sshlab]$ chmod 600 ~/.ssh/config
[student@workstation sshlab]$ ssh opsa 'echo hello from $(hostname) as $USER'
hello from servera.lab.example.com as ops

Appending (>>) keeps any other entries the lab already keeps in that file.

Upload with scp

Copy inventory.txt to the home directory of ops, and reports (the directory) to /tmp. Verify both on servera.

[student@workstation sshlab]$ scp inventory.txt opsa:
[student@workstation sshlab]$ scp -r reports opsa:/tmp/
[student@workstation sshlab]$ ssh opsa 'ls -l ~/inventory.txt; ls /tmp/reports'
-rw-r--r--. 1 ops ops 15 Oct  3 16:49 /home/ops/inventory.txt
a.txt
b.txt

Download with scp and sftp

Download /etc/hostname from servera as servera-hostname.txt. Then use sftp to fetch /tmp/reports/a.txt.

[student@workstation sshlab]$ scp opsa:/etc/hostname ./servera-hostname.txt
[student@workstation sshlab]$ cat servera-hostname.txt
servera.lab.example.com
[student@workstation sshlab]$ sftp opsa
sftp> cd /tmp
sftp> ls reports
reports/a.txt   reports/b.txt
sftp> get reports/a.txt downloaded-a.txt
Fetching /tmp/reports/a.txt to downloaded-a.txt
sftp> bye

Synchronise with rsync

Synchronise the contents of reports/ into rsyncdir/ in the home of ops. Run the same command again, then add a third file and run it a third time. Compare what each run reports.

[student@workstation sshlab]$ rsync -av reports/ opsa:rsyncdir/
sending incremental file list
created directory rsyncdir
./
a.txt
b.txt

sent 191 bytes  received 88 bytes  558.00 bytes/sec
total size is 6  speedup is 0.02
[student@workstation sshlab]$ rsync -av reports/ opsa:rsyncdir/
sending incremental file list

sent 117 bytes  received 19 bytes  272.00 bytes/sec
total size is 6  speedup is 0.04
[student@workstation sshlab]$ echo r3 > reports/c.txt
[student@workstation sshlab]$ rsync -av reports/ opsa:rsyncdir/
sending incremental file list
./
c.txt

sent 166 bytes  received 38 bytes  408.00 bytes/sec
total size is 9  speedup is 0.04

Each run sent only what was new. Your byte counts may differ slightly.

Preview a mirror before you do it

Delete reports/b.txt locally. Use a dry run to see what --delete would do on the server, then run it for real and check.

[student@workstation sshlab]$ rm reports/b.txt
[student@workstation sshlab]$ rsync -avn --delete reports/ opsa:rsyncdir/
sending incremental file list
deleting b.txt
./

sent 113 bytes  received 35 bytes  98.67 bytes/sec
total size is 6  speedup is 0.04 (DRY RUN)
[student@workstation sshlab]$ rsync -av --delete reports/ opsa:rsyncdir/
sending incremental file list
deleting b.txt
./

sent 113 bytes  received 35 bytes  296.00 bytes/sec
total size is 6  speedup is 0.04
[student@workstation sshlab]$ ssh opsa ls rsyncdir
a.txt
c.txt

Always add -n first when --delete is involved.

Grade and finish

Check your work with lab grade sa-transfer, then put the exercise away with lab finish sa-transfer.