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Permission denied - running script

rated 0 times [ 1] [ 0] / answers: 1 / hits: 1673 / 1 Year ago, tue, november 29, 2022, 2:56:39

I am new somewhat to scripting in Ubuntu and I have the following script which I am executing but getting back Permission Denied messages. Any help is greatly appreciated!

Here's the sequence:

The Script:

!/tm/local/bin/bash

blockdev --setra 16384 /dev/sd[bcdefghijkl]

echo 1024 > /sys/block/sdb/queue/read_ahead_kb

echo 1024 > /sys/block/sdc/queue/read_ahead_kb

echo 1024 > /sys/block/sdd/queue/read_ahead_kb

echo 1024 > /sys/block/sde/queue/read_ahead_kb

echo 1024 > /sys/block/sdf/queue/read_ahead_kb

echo 1024 > /sys/block/sdg/queue/read_ahead_kb

echo 1024 > /sys/block/sdh/queue/read_ahead_kb

echo 1024 > /sys/block/sdi/queue/read_ahead_kb

echo 1024 > /sys/block/sdj/queue/read_ahead_kb

echo 1024 > /sys/block/sdk/queue/read_ahead_kb

echo 256 > /sys/block/sdb/queue/nr_requests

echo 256 > /sys/block/sdc/queue/nr_requests

echo 256 > /sys/block/sdd/queue/nr_requests

echo 256 > /sys/block/sde/queue/nr_requests

echo 256 > /sys/block/sdf/queue/nr_requests

echo 256 > /sys/block/sdg/queue/nr_requests

echo 256 > /sys/block/sdh/queue/nr_requests

echo 256 > /sys/block/sdi/queue/nr_requests

echo 256 > /sys/block/sdj/queue/nr_requests

echo 256 > /sys/block/sdk/queue/nr_requests

# Set read-ahead.

echo "Setting read-ahead to 64 MiB for /dev/md0"

blockdev --setra 65536 /dev/md0

# Set stripe-cache_size for RAID6.

echo "Setting stripe_cache_size to 16 MiB for /dev/md0"

echo 16384 > /sys/block/md0/md/stripe_cache_size

echo 8192 > /sys/block/md0/md/stripe_cache_active

# Disable NCQ on all disks.

echo "Disabling NCQ on all disks..."

echo 1 > /sys/block/sdb/device/queue_depth

echo 1 > /sys/block/sdc/device/queue_depth

echo 1 > /sys/block/sdd/device/queue_depth

echo 1 > /sys/block/sde/device/queue_depth

echo 1 > /sys/block/sdf/device/queue_depth

echo 1 > /sys/block/sdg/device/queue_depth

echo 1 > /sys/block/sdh/device/queue_depth

echo 1 > /sys/block/sdi/device/queue_depth

echo 1 > /sys/block/sdj/device/queue_depth

echo 1 > /sys/block/sdk/device/queue_depth

I gave everyone execution access like this:

chmod a+x /home/tm/raid-sync.sh

I execute it like this:

root@LSERVER:~# sh /home/tm/raid-sync.sh

It returns this:

/home/tm/raid-sync.sh: 1: /home/tm/raid-sync.sh: !/tm/local/bin/bash: not found

Setting read-ahead to 64 MiB for /dev/md0

Setting stripe_cache_size to 16 MiB for /dev/md0

/home/tm/raid-sync.sh: 29: /home/tm/raid-sync.sh: cannot create /sys/block/md0/md/stripe_cache_active: Permission denied

Disabling NCQ on all disks...

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3 Years ago

answered 1 Year ago herriail · Accepted Answer

First, to escape by first error (!/tm/local/bin/bash: not found), change !/tm/local/bin/bash with #!/bin/bash. See here more about shebang (what it is, how to use it, examples).

Second, if you set executing permissions to the script, then run it only using /home/tm/raid-sync.sh at the prompt (without sh in front).

Third, the /sys directory in Linux is deceptive. Unlike most other directories, it does not provide persistent storage for arbitrary files and because of this you don't have permission to write even if you are root. See this answer for more info.