mjhjmtu

Platform: Linux
Bash shell

Need help in modify only 2nd column i.e mount points of NAS share /vol/wrm6 in /etc/fstab file.

NAS1:/vol/wrm6 /archive/net1 NFS default 0 0
NAS2:/vol/wrm6 /archive/06 NFS default 0 0
NAS3:/vol/wrm7 /archive/07 NFS default 0 0
 NAS4:/vol/wrm8 /archive/09 NFS default 0 0

The paths should be modified to have a suffix on the second column:

NAS1:/vol/wrm6 /archive/net1_05042018 NFS default 0 0
NAS2:/vol/wrm6 /archive/06_05042018 NFS default 0 0
 NAS3:/vol/wrm7 /archive/07 NFS default 0 0
 NAS4:/vol/wrm8 /archive/09 NFS default 0 0

requirement is whatever dir under /archive/ for NAS share /vol/wrm6 get appended _05042018 like /archive/*_05042018. * means may be any dir

This should take care of what you want and will add the _05042018 to all directories that fall under archive when they involve wrm6.

sed -i -E "s/(.*wrm6[[:space:]]+/archive/)(.+)([[:space:]]+NFS.*)/12_050420183/g" /etc/fstab

The following script would

1. check that the new mount points actually exists (and abort otherwise),


2. make a dated backup of the existing /etc/fstab file, and finally


3. modify the /etc/fstab file.

I would recommend to run it on a copy of the fstab file a few times to make sure that it works on your system. Just change the fstab variable at the top of the script to point to a different file.

The script only adds a suffix to the mount point. It doesn't try to remove it if there is already one there.

#!/bin/sh

set -e # terminate on errors (don't remove!)

fstab='/etc/fstab' # these could be made command line arguments
device_pattern='^NAS[0-9]:/vol/wrm6' # but I kept them like this for simplicity
dir_pattern='^/archive/'
suffix='_05042018'

# Check for non-existing mount points
awk -v suf="$suffix" -v dev="$device_pattern" -v dir="$dir_pattern" 
 '$1 ~ dev && $2 ~ dir print NR, $1, $2 suf ' "$fstab" |
while read lineno device mtpoint; do
 if [ ! -d "$mtpoint" ]; then
 printf 'Mount point "%s" for "%s" is missing on line %d of %sn' 
 "$mtpoint" "$device" "$lineno" "$fstab" >&2
 #exit 1
 fi
done

# Make backup
bkname="$fstab-backup.$(date +%F_%H%M%S)"
cp "$fstab" "$bkname"

# Modify file
awk -v suf="$suffix" -v dev="$device_pattern" -v dir="$dir_pattern" 
 '$1 ~ dev && $2 ~ dir $2 = $2 suf 1' "$bkname" >"$fstab"

echo 'Done.'
echo 'New fstab:'
cat "$fstab"

The "don't remove!" comment is for real. If set -e is removed, then the script would not terminate if an invalid mount point is found (at least when running under bash or pdksh).