Solid-State Society

Month: November 2017

  • Run Process in Background and Redirect Output to a Log – The Ease Way

    $ some_cmd > some_cmd.log 2>&1 &

    Source: https://unix.stackexchange.com/a/106641

  • Install Transmission on CentOS 7

    Nowadays it’s really simple to install Transmission on CentOS 7 or EL distro. First you need to install EPEL packages:

    $ yum install epel-release
$ yum -y update

    …or use the following command if you’re running Red Hat Enterprise Linux:

    $ yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-$(rpm -E '%{rhel}').noarch.rpm

    Install Transmission:

    $ yum install transmission-cli transmission-common transmission-daemon

    Create storage directory:

    $ mkdir /ebs-data/transmission/
$ chown -R transmission.transmission /ebs-data/transmission/

    Start and stop the Transmission to auto generate configs:

    $ systemctl start transmission-daemon.service
$ systemctl stop transmission-daemon.service

    To edit the config, you MUST first stop the daemon, otherwise the config will be overwritten after you restart the daemon:

    $ systemctl stop transmission-daemon.service
$ var /var/lib/transmission/.config/transmission-daemon/settings.json

    Edit config:

    "download-dir": "/ebs-data/transmission",
"incomplete-dir": "/ebs-data/transmission",
"rpc-authentication-required": true,
"rpc-enabled": true,
"rpc-password": "my_password",
"rpc-username": "my_user",
"rpc-whitelist": "0.0.0.0",
"rpc-whitelist-enabled": false,

    Save and start daemon:

    $ systemctl start transmission-daemon.service

    Access via your browser:

    $ open http://localhost:9091/transmission/web/

  • Mount EBS Volumes To EC2 Linux Instances

    View all available volumes:

    $ lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
xvda    202:0    0   10G  0 disk 
├─xvda1 202:1    0    1M  0 part 
└─xvda2 202:2    0   10G  0 part /
xvdf    202:80   0  3.9T  0 disk 

    $ file -s /dev/xvdf
/dev/xvdf: data

    If returns data it means the volume is empty. We need to format it first:

    $ mkfs -t ext4 /dev/xvdf
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
262144000 inodes, 1048576000 blocks
52428800 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=3196059648
32000 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
    4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 
    102400000, 214990848, 512000000, 550731776, 644972544

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

    Create a new directory and mount it to EBS volume:

    $ cd / && mkdir ebs-data
$ mount /dev/xvdf /ebs-data/

    Check volume mount:

    $ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/xvda2       10G  878M  9.2G   9% /
devtmpfs        476M     0  476M   0% /dev
tmpfs           496M     0  496M   0% /dev/shm
tmpfs           496M   13M  483M   3% /run
tmpfs           496M     0  496M   0% /sys/fs/cgroup
tmpfs           100M     0  100M   0% /run/user/1000
tmpfs           100M     0  100M   0% /run/user/0
/dev/xvdf       3.9T   89M  3.7T   1% /ebs-data

    In order to make it mount automatically after each reboot, we need to edit /etc/fstab, first make a backup:

    $ cp /etc/fstab /etc/fstab.orig

    Find the UUID for the volume you need to mount:

    $ ls -al /dev/disk/by-uuid/
total 0
drwxr-xr-x. 2 root root 80 Nov 25 05:04 .
drwxr-xr-x. 4 root root 80 Nov 25 04:40 ..
lrwxrwxrwx. 1 root root 11 Nov 25 04:40 de4dfe96-23df-4bb9-ad5e-08472e7d1866 -> ../../xvda2
lrwxrwxrwx. 1 root root 10 Nov 25 05:04 e54af798-14df-419d-aeb7-bd1b4d583886 -> ../../xvdf

    Then edit /etc/fstab:

    $ vi /etc/fstab

    with:

    #
# /etc/fstab
# Created by anaconda on Tue Jul 11 15:57:39 2017
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=de4dfe96-23df-4bb9-ad5e-08472e7d1866 /                       xfs     defaults        0 0
UUID=e54af798-14df-419d-aeb7-bd1b4d583886 /ebs-data               ext4    defaults,nofail 0 2

    Check if fstab has any error:

    $ mount -a

  • Use cURL to view request headers

    curl -v -s -o - -X OPTIONS https://www.google.com/