On Mar 21, 2019, at 9:57 AM, Lukas Czerner <lczerner@xxxxxxxxxx> wrote:
>
> So the good news is that it's not really a problem. What you really want
> is the mountpoint if it exists and the device otherwise right ?
>
> Then my suggestion will do just that becuase awk will separate the fieds
> with FS (field separator) which by default is a single space. But space
> is special in awk becuase the fields will be separated by a runs of
> space, so if you pick the fileds just right you'll get what you want.
>
> So if I run this on my system
>
> # lsblk -o MOUNTPOINT,NAME,FSTYPE -p -n -l `lvs -o lv_path -S lv_active=active,lv_role=public,lv_role!=snapshot,vg_free\>256 --noheadings`
>
> I'll get
>
> /dev/mapper/vg_perpetuum-ext4--suck
> /dev/mapper/vg_perpetuum-fedora29
> /dev/mapper/vg_perpetuum-fedora29--2
> /dev/mapper/vg_perpetuum-freebsd
> /mnt/kernel /dev/mapper/vg_perpetuum-kernel ext4
> /home /dev/mapper/vg_perpetuum-lv_home xfs
> / /dev/mapper/vg_perpetuum-lv_root xfs
> [SWAP] /dev/mapper/vg_perpetuum-lv_swap swap
> /var /dev/mapper/vg_perpetuum-lv_var xfs
> /dev/mapper/vg_perpetuum-lvol001 ext4
> /dev/mapper/vg_perpetuum-overlay ext4
> /dev/mapper/vg_perpetuum-rhel7
> /dev/mapper/vg_perpetuum-rhel8
> /dev/mapper/vg_perpetuum-test0 ext3
> /dev/mapper/vg_perpetuum-testing ext4
> /dev/mapper/vg_perpetuum-testing1 xfs
> /dev/mapper/vg_perpetuum-thinvolume
>
> now if I add
>
> | awk '{print $1}'
>
> I'll get
>
> /dev/mapper/vg_perpetuum-ext4--suck
> /dev/mapper/vg_perpetuum-fedora29
> /dev/mapper/vg_perpetuum-fedora29--2
> /dev/mapper/vg_perpetuum-freebsd
> /mnt/kernel
> /home
> /
> [SWAP]
> /var
> /dev/mapper/vg_perpetuum-lvol001
> /dev/mapper/vg_perpetuum-overlay
> /dev/mapper/vg_perpetuum-rhel7
> /dev/mapper/vg_perpetuum-rhel8
> /dev/mapper/vg_perpetuum-test0
> /dev/mapper/vg_perpetuum-testing
> /dev/mapper/vg_perpetuum-testing1
> /dev/mapper/vg_perpetuum-thinvolume
>
>
> hence I get mountpoin where the volume is mounted and the device where
> it is not. That's what we need right ?
>
> What I did not consider was [SWAP] but we can get rid of that easily.
>
> grep -v '[SWAP]'
>
> So in the end we'll have something like
>
> # lsblk -o MOUNTPOINT,NAME,FSTYPE -p -n -l `lvs -o lv_path -S lv_active=active,lv_role=public,lv_role!=snapshot,vg_free\>256 --noheadings` | grep -v '[SWAP]' | grep ' ext[234]$' | awk '{print $1}'
This doesn't need to skip [SWAP] explicitly because it will not have an ext[234]
filesystem mounted on it, so would be excluded by the next "grep" anyway.
However, if you are using "awk" then there is no need for the extra grep(2) I think.
Something like the following looks like it will work:
lsblk -o MOUNTPOINT,NAME,FSTYPE -p -n -l $(lvs -o lv_path \
-S lv_active=active,lv_role=public,lv_role!=snapshot,vg_free\>256 --noheadings) |
awk '($NF > 1 && $2 == ext[234]) || ($NF > 2 && $3 == ext[234]) { print $1 }'
The "$NF" checks appear to be needed because "$3 = ext[234]" seems to match everything
if "$3" is empty, though I can't understand why that would be desirable.
> and so on my system this gives me
>
> /mnt/kernel
> /dev/mapper/vg_perpetuum-lvol001
> /dev/mapper/vg_perpetuum-overlay
> /dev/mapper/vg_perpetuum-test0
> /dev/mapper/vg_perpetuum-test10
> /dev/mapper/vg_perpetuum-test11
> /dev/mapper/vg_perpetuum-test3
> /dev/mapper/vg_perpetuum-test4
> /dev/mapper/vg_perpetuum-test9
> /dev/mapper/vg_perpetuum-testing
>
> And leaving out mounted file systems is again as simple as
>
> grep -v '^/dev/'
>
> Have I missed something ?
>
>
> Now for the performance. I drop caches, then run each twice
>
> the ls_scan_targets function runs
>
> real 0m0.575s
> user 0m0.086s
> sys 0m0.179s
>
> real 0m0.241s
> user 0m0.088s
> sys 0m0.169s
>
>
> My one-line suggestion runs
>
> real 0m0.275s
> user 0m0.027s
> sys 0m0.047s
>
> real 0m0.069s
> user 0m0.015s
> sys 0m0.052s
>
>
> So the difference is significant, although I would not consider it
> meaningful since it's really low anyway, but some people complained so I
> guess someone cares and people do have different systems so...
>
>>
>> :-)
>>
>> We could have used awk to select the field, but that still doesn't
>> deal with the mountpoint column being empty when it is unmounted. I
>> did briefly consider using lsblk -J, but I didn't want to add a
>> dependency on the jq[1] package (and I didn't even know if RHEL/Fedora
>> packages jq).
>>
>> [1] https://packages.debian.org/stretch/jq
>
> Yes Fedora does have it, but I agree that adding this dependency is not
> ideal.
>
> Thanks!
> -Lukas
>
>>
>> Cheers,
>>
>> - Ted
Cheers, Andreas
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