cp -a: copy a directory and preserve timestamps, permissions and links

cp -a SOURCE DEST copies files and whole directory trees while keeping their metadata: modification times, permission bits, ownership (when you are root), symbolic links as links, hard links between copied files, and extended attributes. In GNU cp it is shorthand for -dR --preserve=all. Use it for backups, moving a data directory to a new disk, or any copy that must look identical to the original. A plain cp refuses directories (see cp: -r not specified; omitting directory) and stamps every copy with the current time.

Plain cp vs cp -a

mkdir -p src/sub
echo hello > src/sub/notes.txt
touch -d '2020-01-02 03:04:05 UTC' src/sub/notes.txt
cp src/sub/notes.txt plain.txt
cp -a src/sub/notes.txt archived.txt
for f in plain.txt archived.txt; do
  if [ "$f" -nt src/sub/notes.txt ]; then echo "$f: new timestamp"; else echo "$f: $(date -u -r "$f" '+%F %T')"; fi
done
cp src copy-plain; echo "exit: $?"
cp -a src copy-a; find copy-a | sort

plain.txt: new timestamp
archived.txt: 2020-01-02 03:04:05
cp: -r not specified; omitting directory 'src'
exit: 1
copy-a
copy-a/sub
copy-a/sub/notes.txt

Plain cp gives the file the time of the copy and refuses the directory; cp -a keeps the 2020 timestamp and copies the tree recursively.

What -a turns on

On macOS and the BSDs cp -a exists too and is equivalent to -RpP: recursive, preserve attributes, do not follow links. It is not in POSIX, which defines only -R and -p, so very old or minimal systems may lack it.

The existing-destination pitfall

cp -a src dest behaves differently depending on whether dest already exists:

mkdir -p src
echo one > src/a.txt
cp -a src dest
cp -a src dest
find dest | sort
echo '--- contents only'
cp -a src/. dest2
find dest2 | sort

dest
dest/a.txt
dest/src
dest/src/a.txt
--- contents only
dest2
dest2/a.txt

The second run copied src into dest, producing dest/src. Writing src/. copies the contents, so the command gives the same result every time. rsync -a has the same distinction through its trailing slash rule.

Platform notes

• In Git Bash on Windows, permission bits are emulated, so -a mostly preserves timestamps; ownership is meaningless there, and symbolic links are copied as regular files unless native symlinks are enabled.
• Preserving ownership needs root. As a normal user cp -a gives the copies your user and group.
• cp -a shows no progress and restarts from zero if interrupted. For large or remote copies, rsync -a can resume and skip unchanged files.
• Combine with -v to list each copied path, or -n to avoid overwriting files that are already in the destination.

FAQ