tipcc-backup: tools for checking and comparing to /backup

[HenrikBengtsson]

Gist:

tipcc_backup_dir_diff() {
  BACKUP=/backup/home.20190816
  diff -wu <(ls -la $BACKUP/${PWD/\/home//}) <(ls -la $PWD)
}

[HenrikBengtsson]

diff -rq a/ b/ (== diff --recursive --brief) can be used to compare file content of two folders a/ and b/. This can be used to for instance identify lost files, or modified files.

However, we have to be careful with the output, because diff -rq will not report on missing files if a whole folder is lost - only the lost folder. Here's an example.

Let's create a backup folder and a home folder where we lost some files and folders:

mkdir -p backup/A backup/B backup/C backup/D
touch backup/file01 backup/B/file{02,03,04} backup/C/file{05,06}
cp -pR backup home
rm -rf home/B/  ## emulate lost folder
rm home/C/file05  ## emulate some lost files in folder
rm -rf home/D/  ## emulate a lost empty folder

such that we have:

$ $ tree backup
backup
├── A
├── B
│   ├── file02
│   ├── file03
│   └── file04
├── C
├── D
│   ├── file05
│   └── file06
└── file01

4 directories, 6 files

and

$ tree home
home
├── A
├── C
│   └── file06
└── file01

2 directories, 2 files

Running diff -rq on the above gives:

$ diff -rq home/ backup/
Only in backup/: B
Only in backup/C: file05
Only in backup/: D

Note, we only get reports on B/, but not B/file02, B/file03, and B/file04, when we loose all files in a folder. Because of this, we need to do further investigation on folders B/ and D/ to know what is actually missing/different.

[HenrikBengtsson]

Test of diff -rq with symbolic links:

mkdir -p backup/A backup/B backup/C backup/D
touch backup/file01 backup/B/file{02,03,04} backup/C/file{05,06}
ln -fs ../data2 backup/data2
ln -fs ../data1 backup/data1
cp -pR backup home
rm -rf home/B/  ## emulate lost folder
rm home/C/file05  ## emulate some lost files in folder
rm -rf home/D/  ## emulate a lost empty folder
rm backup/data2  ## emulate lost symbolic link

gives:

$ diff -rq home/ backup/
Only in backup/: B
Only in backup/C: file05
Only in backup/: D
Only in home/: data2

Result: Seems to work.