Master Secure Copy and Rsync: Essential Tips, Parameters, and Best Practices

scp (secure copy) is a Linux command for remote file copying, similar to cp but works across servers and encrypts data.

When a server's filesystem becomes read‑only, scp can be used to retrieve files. It consumes minimal resources compared with rsync, which may cause higher I/O on many small files.

Generally rsync is preferred for synchronization because it transfers only differences, supports incremental backups, and can compare file modification time and size. Rsync transfers changed blocks, while scp transfers whole files. Rsync is not encrypted by default, whereas scp provides encrypted transfer.

SCP common options

-B  Batch mode (no password prompts)</code>
<code>-C  Enable compression (passes -C to ssh)</code>
<code>-p  Preserve modification, access times and permissions</code>
<code>-q  Suppress progress meter</code>
<code>-r  Recursively copy directories</code>
<code>-v  Verbose output (debug information)</code>
<code>-c cipher  Specify encryption cipher (passed to ssh)</code>
<code>-F ssh_config  Use alternative ssh configuration file</code>
<code>-i identity_file  Use private key file for authentication</code>
<code>-l limit  Limit bandwidth in Kbit/s</code>
<code>-o ssh_option  Pass ssh options</code>
<code>-P port  Specify remote port (uppercase P)</code>
<code>-S program  Specify program for encrypted transport

Rsync common options

-a, --archive  Archive mode; recursive, preserve attributes (equivalent to -rlptgoD)</code>
<code>-v, --verbose  Verbose output</code>
<code>-p, --perms  Preserve permissions</code>
<code>-g, --group  Preserve group</code>
<code>-o, --owner  Preserve owner</code>
<code>-r, --recursive  Recurse into directories</code>
<code>-l, --links  Preserve symbolic links</code>
<code>-H, --hard-links  Preserve hard links</code>
<code>-e, --rsh=COMMAND  Specify remote shell (ssh)</code>
<code>-z, --compress  Compress file data during transfer</code>
<code>--stats  Show transfer statistics</code>
<code>--progress  Show progress during transfer</code>
<code>--timeout=TIME  Set I/O timeout in seconds</code>
<code>--delete  Delete files in destination that are absent in source</code>
<code>--delete-before  Delete before receiving files</code>
<code>--delete-after  Delete after transfer</code>
<code>--delete-excluded  Delete excluded files from destination</code>
<code>--ignore-errors  Continue despite I/O errors</code>
<code>--exclude PATTERN  Exclude files matching pattern</code>
<code>--exclude-from FILE  Read exclude patterns from FILE</code>
<code>--version  Show version</code>
<code>--port=PORT  Specify rsync daemon port</code>
<code>--log-format=FORMAT  Define log format</code>
<code>--password-file=FILE  Read password from FILE</code>
<code>--bwlimit=KBPS  Limit I/O bandwidth

Practical tips for remote copying

1. Handling symbolic links

Rsync copies symlinks when the -l option is used. SCP does not preserve symlinks; to copy them you can archive the source directory with tar -zcvf test.tar.gz test, transfer the archive, then extract it on the target.

2. Showing progress

Rsync displays a progress bar with --progress. SCP shows progress when the -v (verbose) flag is used, even across machines; without -v it shows no progress.

3. Bandwidth limiting

Rsync limits bandwidth with --bwlimit=KBPS (e.g., --bwlimit=1000 for 1 MB/s). SCP limits bandwidth with the -l option (e.g., -l 1024 for 1 MB/s).

4. Filtering files

Rsync can exclude files or directories using --exclude=PATTERN or --exclude-from=FILE. Patterns must be simple names, not full paths, and can include wildcards. Multiple --exclude options can be combined.

5. Copying hidden files

To copy hidden files with rsync, include a trailing slash on the source directory (e.g., rsync -av /path/to/source/ user@host:/path/to/dest/). With SCP, use scp -rp -P 22 /path/to/source/. user@host:/path/to/dest/ to include dotfiles.

For more details, see the original article: https://www.cnblogs.com/kevingrace/p/8529792.html