https://dengxihe.com/techwiki/ 2026-04-25T12:36:33-07:00 https://dengxihe.com/techwiki/ https://dengxihe.com/techwiki/lib/tpl/dokuwiki/images/favicon.ico text/html 2017-01-18T17:39:03-07:00 https://dengxihe.com/techwiki/linux/audio?rev=1484789943&do=diff Audio Issues * Play mp3 in command line * Packages - alsa alsa-lib * Only root can read the audio device - Add regular user to “audio” group * Volume control - “alsamixer”, left/right, up/down to adjust the volume * Play mp3 in command line - ffplay from ffmpeg, play from sox with libsox-fmt-mp3 text/html 2018-04-20T15:36:53-07:00 https://dengxihe.com/techwiki/linux/boot?rev=1524263813&do=diff Boot Grub * Grub 2 - Setting default entry Open /etc/default/grub and ensure this line exists: GRUB_DEFAULT=saved Apply the change to grub.cfg by running: # grub2-mkconfig -o /boot/grub2/grub.cfg Now list all possible menu entries # grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2 Now set the desired default menu entry # grub2-set-default <menu entry title> Verify the default menu entry # grub2-editenv list text/html 2017-03-08T12:16:59-07:00 https://dengxihe.com/techwiki/linux/btrfs?rev=1489004219&do=diff # mkfs.btrfs -L data /dev/sda4 # btrfs filesystem show # mount /dev/sda4 /data # btrfs filesystem df /data # btrfs filesystem usage /data add new device # btrfs device add /dev/xvdb / # btrfs filesystem balance / Done, had to relocate 7 out of 7 chunks text/html 2017-01-18T17:42:41-07:00 https://dengxihe.com/techwiki/linux/disk?rev=1484790161&do=diff Disk Partition UUID and Label * Get UUID and Label # blkid /dev/sda1: SEC_TYPE="msdos" UUID="62AC-64E2" TYPE="vfat" /dev/sda2: UUID="ebc16f0e-586d-466e-aba5-321016b401e9" TYPE="ext4" /dev/sda3: UUID="9bb04b5a-e6c8-48ae-b802-4084f3943945" TYPE="xfs" /dev/sda4: UUID="439969cb-2311-40e9-b1bc-6ede1bd185ef" TYPE="swap" /dev/sdc1: UUID="6450978C50976398" TYPE="ntfs" /dev/sdc2: UUID="fc5d0b9e-6092-410d-b000-c567be2eb940" TYPE="ext4" /dev/sdb1: UUID="665d6352-b050-4702-b4f0-c6242c785127" TYPE="xfs" text/html 2017-01-19T10:28:12-07:00 https://dengxihe.com/techwiki/linux/myubuntu?rev=1484850492&do=diff java in Ubuntu <https://launchpad.net/~webupd8team/+archive/ubuntu/java> <http://www.webupd8.org/2012/01/install-oracle-java-jdk-7-in-ubuntu-via.html> 3TB Seaga HD failure Error in /var/log/syslog Dec 30 14:26:23 homeserver kernel: [43971969.493019] ata3.00: BMDMA stat 0x25 Dec 30 14:26:23 homeserver kernel: [43971969.494077] ata3.00: failed command: READ DMA EXT Dec 30 14:26:23 homeserver kernel: [43971969.495077] ata3.00: cmd 25/00:00:d8:1f:6c/00:04:28:00:00/e0 tag 0 dma 524288 in Dec 30 1… text/html 2017-09-18T17:37:48-07:00 https://dengxihe.com/techwiki/linux/network?rev=1505781468&do=diff ip command set static ip # ip addr add 192.168.0.100/22 dev eth0 del static IP # ip addr del 192.168.0.100/22 dev eth0 del all IP # ip addr flush dev eth0 set mtu # ip link set dev eth0 mtu 9000 create a bridge # brctl addbr br0 # brctl addif br0 eth0 # ip addr del 192.168.0.100/24 dev eth0 # ip link set up dev br0 # ip addr add 192.168.0.100/24 dev br0 # brctl show text/html 2017-01-18T17:56:21-07:00 https://dengxihe.com/techwiki/linux/ocfs2?rev=1484790981&do=diff * Create file system * Local # mkfs.ocfs2 -M local -T [vmstore|datafiles|emails|] -L [lable] device On OVS # mkfs.ocfs2 -J block64 -b 4096 -L <label> -U <uuid> -T vmstore -N 32 -M local * Get ocfs2 fs information * Local # tunefs.ocfs2 -Q "Label: %V\nUUID: %U\nBlock size: %B bytes\nCluster size: %T bytes\nNumber of node slots: %N\nFlags: %M %H %O\n" /dev/mapper/35000cca01646b4a8 Label: ovmstore UUID: 1378EF40C752489C8216F0979EDC8CEB Block size: 4096 bytes Cluster size: 1048576… text/html 2017-01-18T17:46:46-07:00 https://dengxihe.com/techwiki/linux/perf?rev=1484790406&do=diff Performance * Enable “Uncore Frequency Scaling” in BIOS CPU power management configuration. * create CPU work load # taskset -c 0 openssl speed * Check turbo boost # turbostat # pcm * Set CPU frequency policy # cpupower frequency-set -g performance text/html 2017-09-15T17:40:08-07:00 https://dengxihe.com/techwiki/linux/serial_console?rev=1505522408&do=diff RHEL/Centos/OL 7.X Baremetal cat /etc/default/grub GRUB_TIMEOUT=5 GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)" GRUB_DEFAULT=saved GRUB_DISABLE_SUBMENU=true #GRUB_TERMINAL_OUTPUT="console" GRUB_TERMINAL="console serial" GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1" GRUB_CMDLINE_LINUX="crashkernel=auto console=tty1 console=ttyS0,115200" GRUB_DISABLE_RECOVERY="true" GRUB_GFXPAYLOAD_LINUX=text text/html 2017-01-24T11:22:34-07:00 https://dengxihe.com/techwiki/linux/ssh?rev=1485285754&do=diff SSH generate key $ ssh-keygen -t rsa -b 4096 ssh agent If your private key is encrypted with a passphrase(when you generate it by ssh-keygen), the passphrase must be entered every time you attempt to connect to an SSH server using public-key authentication. text/html 2017-02-03T21:54:20-07:00 https://dengxihe.com/techwiki/linux/yum?rev=1486187660&do=diff Yum download packages # yum install yum-utils # yumdownloader <packagename> # yumdownloader --source <packagename> Yum group install OL6 # yum grouplist Setting up Group Process ol6_latest/group | 1.1 MB 00:01 Installed Groups: E-mail server Available Groups: Additional Development Backup Client …