[SOLVED] Unable to edit fstab with sed to edit mount options

Honest Abe · 03-14-2019, 06:04 PM

Thanks a lot for your help and direction.
Currently, I have settled for this, though it is not perfect.

Original File

Code:

# Commented Line followed by empty line

/dev/mapper/vg_root-lv_root     /       ext4    defaults 1 2
UUID=STRING1       /boot   ext4    defaults 1 2
/dev/mapper/vg_root-lv_home     /home   ext4    defaults 1 2
/dev/mapper/vg_root-lv_opt      /opt    ext4    defaults 1 2
# Commented Line followed by empty line

/dev/mapper/vg_root-lv_tmp      /tmp    ext4    defaults,noexec         1       2
/dev/mapper/vg_root-lv_usr      /usr    ext4    defaults 1 2
/dev/mapper/vg_root-lv_var      /var    ext4    defaults 1 2
/dev/mapper/vg_root-lv_swap     swap    swap    defaults 1 2
tmpfs   /dev/shm        tmpfs   nodev,nosuid,noexec     0       0
devpts  /dev/pts        devpts  STRING2  0       0
sysfs   /sys    sysfs   defaults 1 2
proc    /proc   proc    defaults 1 2
/tmp    /var/tmp        none    bind,nodev,nosuid,noexec    0      0
/dest1  /MP1    ext4    defaults,nodev 1 2
/dest2         /MP2      ext3    noexec 1 2
# Commented Line followed by empty line

/dest3           /MP3                  ext4    defaults        1       2

script

Code:

 cat /tmp/fstab_bk | while read line;do if [[ $line == *"vg_root"*  ||  $line == *"UUID"* ||  $line == "^#"* ||  $line == *"nosuid"* || $line == *"proc*"  || $line == *"sysfs"*  ||  $line == *"devpts"* ]]; then echo "$line" >> fstab_new; else echo "$line" | awk ' /^$/ { next }{ $4 = $4 ",nosuid"; print $0 }' >> fstab_new ;fi;done;

Output

Code:

# Commented Line followed,nosuid by empty line
/dev/mapper/vg_root-lv_root     /       ext4    defaults 1 2
UUID=STRING1       /boot   ext4    defaults 1 2
/dev/mapper/vg_root-lv_home     /home   ext4    defaults 1 2
/dev/mapper/vg_root-lv_opt      /opt    ext4    defaults 1 2
# Commented Line followed,nosuid by empty line
/dev/mapper/vg_root-lv_tmp      /tmp    ext4    defaults,noexec         1       2
/dev/mapper/vg_root-lv_usr      /usr    ext4    defaults 1 2
/dev/mapper/vg_root-lv_var      /var    ext4    defaults 1 2
/dev/mapper/vg_root-lv_swap     swap    swap    defaults 1 2
tmpfs   /dev/shm        tmpfs   nodev,nosuid,noexec     0       0
devpts  /dev/pts        devpts  STRING2  0       0
sysfs   /sys    sysfs   defaults 1 2
proc /proc proc defaults,nosuid 1 2
/tmp    /var/tmp        none    bind,nodev,nosuid,noexec    0      0
/dest1 /MP1 ext4 defaults,nodev,nosuid 1 2
/dest2 /MP2 ext3 noexec,nosuid 1 2
# Commented Line followed,nosuid by empty line
/dest3 /MP3 ext4 defaults,nosuid 1 2

This is very close to what I am looking for. Now if it can just conserve the empty lines and leave the commented lines alone (without adding nosuid to them), it'd be awesome.

MadeInGermany · 03-15-2019, 02:15 PM

More elegant is a case-esac (I also fixed your *"proc*" and "^#" and required "nosuid" in field#4 and others at the begining of the line),
and redirecting the loop's input and output

Code:

while read line; do
  case $line in
  ( *"vg_root"* | "UUID"* | "#"* | "proc"* | "sysfs"* | "devpts"* )
    echo "$line"
  ;;
  ( * )
    echo "$line" | awk 'NF==0 { next } $4!~/nosuid/ { $4 = $4 ",nosuid" } { print }'
  esac
done < /tmp/fstab_bk > fstab.new

pan64 · 03-16-2019, 03:56 AM

Quote:

Originally Posted by MadeInGermany

More elegant is a case-esac (I also fixed your *"proc*" and "^#" and required "nosuid" in field#4 and others at the begining of the line),
and redirecting the loop's input and output

And just because I do not like to implement something using two languages I suggest you to use either awk or shell, but not both.

you can use something like this (if you don't like awk):

Code:

while read -r line; do
  case $line in
  ( *"vg_root"* | "UUID"* | "#"* | "proc"* | "sysfs"* | "devpts"* | *nosuid* )
  ;;
  ( * )
    line=${line/defaults/defaults,nosuid}
  esac
  echo $line
done < /tmp/fstab_bk > fstab.new

Honest Abe · 03-19-2019, 03:58 AM

Quote:

Originally Posted by MadeInGermany

More elegant is a case-esac (I also fixed your *"proc*" and "^#" and required "nosuid" in field#4 and others at the begining of the line),
and redirecting the loop's input and output

Code:

while read line; do
  case $line in
  ( *"vg_root"* | "UUID"* | "#"* | "proc"* | "sysfs"* | "devpts"* )
    echo "$line"
  ;;
  ( * )
    echo "$line" | awk 'NF==0 { next } $4!~/nosuid/ { $4 = $4 ",nosuid" } { print }'
  esac
done < /tmp/fstab_bk > fstab.new

Thanks for the suggestion. Yes, it looks cleaner, though it removes empty lines. (That'd be a bug vs feature debate !!)

pan64 · 03-19-2019, 04:58 AM

so you need to add a line to print them too.

Honest Abe · 03-19-2019, 06:25 AM

@pan64,

Yes, but a residue of Sun Solaris Administration tells me that blank lines in /etc/passwd or /etc/shadow file is not a good practice anyway.
I remember a Solaris 6 (yes, 5.6) server becoming unbootable bcoz someone thought it was a bright idea to add a blank line in topmost position in /etc/shadow (i.e. over the root entry) !!

So I'll call it a feature

pan64 · 03-19-2019, 07:09 AM

yes, that is passwd and shadow files. But /etc/fstab may contain empty lines and comments too. Never mind, it is your decision. From my side it is ok.

MadeInGermany · 03-21-2019, 11:11 AM

I saw your

Code:

 /^$/ { next }

So I thought you intended to delete blank lines and put

Code:

 NF==0 { next }

Meaning: if NumberFields == 0 then skip the following code and jump to the next cycle (next input line).
Simply omit it, and blank lines are printed!

Honest Abe · 03-21-2019, 11:21 AM

Thanks @MadeInGermany, yes, I am aware of that as I had to explain another person what the code was doing. I hope my awk is slightly better now.

This snippet code is part of a function which handles text files containing delimiter separated fields. It's no concern if a blank line gets deleted as long as commented lines don't get messed up.