rear shows misleading "socket ignored" information when tar end with exit code 1

[casantos]

• ReaR version ("/usr/sbin/rear -V"): Relax-and-Recover 2.4 / Git

• OS version ("cat /etc/os-release" or "lsb_release -a" or "cat /etc/rear/os.conf"): Red Hat Enterprise Linux Server release 7.8 (Maipo)

• ReaR configuration files ("cat /etc/rear/site.conf" and/or "cat /etc/rear/local.conf"):

BACKUP=NETFS
BACKUP_URL=file:///backup/
# remove /usr to speed-up the backup
BACKUP_PROG_EXCLUDE=("${BACKUP_PROG_EXCLUDE[@]}" '/usr' '/var/crash' '/var/tmp' '/dev' '/dev/shm' '/run' '/sys/fs/cgroup')

• Hardware (PC or PowerNV BareMetal or ARM) or virtual machine (KVM guest or PoverVM LPAR): KVM guest.

• System architecture (x86 compatible or PPC64/PPC64LE or what exact ARM device): x86_64

• Firmware (BIOS or UEFI or Open Firmware) and bootloader (GRUB or ELILO or Petitboot): UEFI

• Storage (local disk or SSD) and/or SAN (FC or iSCSI or FCoE) and/or multipath (DM or NVMe): VirtIO disks

• Storage layout ("lsblk -ipo NAME,KNAME,PKNAME,TRAN,TYPE,FSTYPE,SIZE,MOUNTPOINT" or "lsblk" as makeshift):

NAME                                 KNAME     PKNAME    TRAN   TYPE FSTYPE       SIZE MOUNTPOINT
/dev/sr0                             /dev/sr0            sata   rom  iso9660      4.2G 
/dev/vda                             /dev/vda                   disk               20G 
|-/dev/vda1                          /dev/vda1 /dev/vda         part vfat         200M /boot/efi
|-/dev/vda2                          /dev/vda2 /dev/vda         part xfs            1G /boot
`-/dev/vda3                          /dev/vda3 /dev/vda         part LVM2_member 18.8G 
  |-/dev/mapper/rhel_rhel--7--1-root /dev/dm-0 /dev/vda3        lvm  xfs         16.8G /
  `-/dev/mapper/rhel_rhel--7--1-swap /dev/dm-1 /dev/vda3        lvm  swap           2G [SWAP]
/dev/vdb                             /dev/vdb                   disk               20G 
`-/dev/vdb1                          /dev/vdb1 /dev/vdb         part xfs           20G /backup

• Description of the issue (ideally so that others can reproduce it):

When tar exits with status greater than zero, rear copies the last 3 messages from the backup.log to its own log. They may also be shown to the user if rear is invoked with the "-v" option. If the last 3 or more messages from tar are "socket ignored" (informational) the actual error message (e.g. "file changed as we read it").

• Workaround, if any: none

• Attachments, as applicable ("rear -D mkrescue/mkbackup/recover" debug log files): N.A.

• Steps to reproduce

1. Set-up /etc/rear/local.conf to save backups in a local filesystem, e.g.

BACKUP=NETFS
BACKUP_URL=file:///backup/
# remove /usr to speed-up the backup
BACKUP_PROG_EXCLUDE=("${BACKUP_PROG_EXCLUDE[@]}" '/usr' '/var/crash' '/var/tmp' '/dev' '/dev/shm' '/run' '/sys/fs/cgroup')

2. Ensure that a daemon that creates sockets is running (e.g. postfix)

# yum install -y postfix
# systemctl enable --now postfix

3. Make a backup of /etc/grub.d/README

# mv /etc/grub.d/README /etc/grub.d/README~
# cp -p /etc/grub.d/README~ /etc/grub.d/README

4. Run rear -v mkbackup while executing a command in parallel to append data to /etc/grub.d/README

# ( while :; do echo .; done ) >> /etc/grub.d/README

5. Stop appending data to /etc/grub.d/README

• Actual results

# rear -v mkbackup
Relax-and-Recover 2.4 / Git
Using log file: /var/log/rear/rear-rhel-7-1.log
Using backup archive '/backup//rhel-7-1/backup.tar.gz'
Using UEFI Boot Loader for Linux (USING_UEFI_BOOTLOADER=1)
Creating disk layout
Excluding component fs:/backup
Using guessed bootloader 'EFI' (found in first bytes on /dev/vda)
Creating root filesystem layout
Trying to find what to use as UEFI bootloader...
Trying to find a 'well known file' to be used as UEFI bootloader...
Using '/boot/efi/EFI/redhat/grubx64.efi' as UEFI bootloader file
Copying logfile /var/log/rear/rear-rhel-7-1.log into initramfs as '/tmp/rear-rhel-7-1-partial-2020-08-03T15:28:45-0300.log'
Copying files and directories
Copying binaries and libraries
Copying kernel modules
Copying all files in /lib*/firmware/
Creating recovery/rescue system initramfs/initrd initrd.cgz with gzip default compression
Created initrd.cgz with gzip default compression (258832181 bytes) in 32 seconds
Making ISO image
Wrote ISO image: /var/lib/rear/output/rear-rhel-7-1.iso (291M)
Copying resulting files to file location
Saving /var/log/rear/rear-rhel-7-1.log as rear-rhel-7-1.log to file location
Creating tar archive '/backup//rhel-7-1/backup.tar.gz'
Archived 568 MiB [avg 10402 KiB/sec] OK
WARNING: tar ended with return code 1 and below output:
  ---snip---
  tar: /var/spool/postfix/public/qmgr: socket ignored
  tar: /var/spool/postfix/public/flush: socket ignored
  tar: /var/spool/postfix/public/showq: socket ignored
  ----------
This means that files have been modified during the archiving
process. As a result the backup may not be completely consistent
or may not be a perfect copy of the system. Relax-and-Recover
will continue, however it is highly advisable to verify the
backup in order to be sure to safely recover this system.

Archived 568 MiB in 57 seconds [avg 10220 KiB/sec]
Exiting rear mkbackup (PID 23976) and its descendant processes
Running exit tasks
(reverse-i-search)`.con': vim -O /etc/rear/local^Conf /usr/share/rear/backup/NETFS/default/500_make_backup.sh

• Expected results:

  ---snip---
  tar: /etc/grub.d/README: file changed as we read it
  ----------

• Additional info

The output is generated in line 235 of /usr/share/rear/backup/NETFS/default/500_make_backup.sh:

$(grep '^tar: ' "${TMP_DIR}/${BACKUP_PROG_ARCHIVE}.log" | sed -e 's/^/  /' | tail -n3)

Rear not only hides the real problem but also shows misleading information, since ignored sockets are not a problem.

[jsmeix]

With #2466 merged this issue is done.

@casantos
thank you for your contribution to ReaR!

[robertdahlem]

While at it: please filter out "Broken symlink" too.