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sololinuxes · 6 years ago

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Preguntas a un Sysadmin

Preguntas a un Sysadmin. Ya tratamos las funciones principales de un Sysadmin (administrador de sistemas) en un articulo anterior, En este articulo veremos otro aspecto sobre su vida cotidiana, las consultas. Es común, incluso llega a ser agotador que un sysadmin reciba cientos de consultas, pueden ser de sus compañeros de oficina, de relaciones personales, amigos, etc... Que levante la mano quien nunca hizo una pregunta a alguien con más conocimientos que el (por lo menos aparentemente), nadie verdad, pues imagínate que te relacionas con un buen sysadmin, y te quieres introducir en ese mundo. Lo vas a bombardear a preguntas, seguro, ja. Hoy hacemos una recopilación de las consultas más frecuentes que recibe un sysadmin, unas son simples, otras no tanto. Comenzamos, no sin antes recordar un articulo donde se exponían los scripts más comunes para un sysadmin. Preguntas a un sysadmin.

Preguntas a un Sysadmin

1- Como forzar la ejecución de fsck al reiniciar el sistema? Para ejecutar fsck de manera forzada en un sistema de archivos (en el próximo reinicio), en el sistema de archivos creamos un nuevo archivo que se llamara 'forcefsck'. Supongamos que queremos ejecutar fsck en el /home. cd /home ; touch forcefsck ; reboot 2- Cambiar la fecha de caducidad de la contraseña de una cuenta, sin modificar la contraseña? Usando el comando "chage" podemos prolongar la fecha de vencimiento sin ningún problema. La sintaxis es la siguiente... chage -d yy-mm-dd Usuario 3- Verificar la última vez que se escaneó un sistema de archivos. Con la herramienta tune2fs, podemos averiguar cuándo se realizó por ultima vez un análisis del sistema de archivos en busca de errores. Su sintaxis es la siguiente. tune2fs -l | grep “Last checked” 4- Qué es Kdump y por qué es tan necesario? Kdump es una herramienta del propio kernel, que captura los volcados de memoria cuando se produce un fallo grave, o un kernel panic. Su beneficio es que puedes analizar esos archivos, y localizar la causa. 5- Qué aplicación se utiliza para analizar los volcado de memoria (o el vmcore) en CentOS? La aplicación para poder analizar los volcados es crash. 6- Como instalar todas actualizaciones y parches del sistema, en un servidor CentOS, excepto el kernel? En este caso tan solo debes utilizar el parámetro exclude de yum o dnf. yum update –exclude=kernel* 7- Como puedo saber si mi servidor es virtual o físico? Para poder identificar y salir de dudas, nos ayudamos de dmidecode. dmidecode -t system | grep “Product Name” 8- Qué es el automounter y por qué es tan necesario? Automounter es un servicio del sistema que se utiliza para montar un sistema de archivos (ya sea local o remoto), al acceder al dispositivo. Cuando el sistema de archivos está inactivo, el servicio (autofs) desmontará automáticamente el sistema de archivos. El beneficio de los autofs es que el sistema no necesita montar el sistema de archivos continuamente, solo montará cuando sea necesario. 9- Como verificar si el ultimo comando se ejecuta correctamente, o no? Es muy fácil, por ejemplo del comando ls. ls -l /var/ echo $? 10- Como puedo forzar a un usuario a cambiar su contraseña? Ayudándonos del comando "chage", lo que haremos es caducar la password del usuario. Así, cada vez que inicie sesión en el sistema recibirá el siguiente aviso, ”Su contraseña ha caducado. Debe cambiar su contraseña ahora e iniciar sesión de nuevo”. chage -d 0 Usuario 11- Como obtener información sobre un paquete rpm con yum? En nuestro ejemplo sobre postfix. yum history package postfix 12- Como modificar el nombre del host de manera permanente en CentOS? Ya tratamos este tema de manera más extensa en otro articulo, de todas maneras es tan simple como ejecutar lo siguiente: hostnamectl set-hostname Nuevo-hostname 13- Como saber que módulos del kernel están instalados? El comando lsmod te dará un completo listado. lsmod 14- Como puedo comprobar la I/O en linux? Existen multitud de herramientas, pero sin dudarlo las más utilizadas son las siguientes (ejecútalas tal cual en tu sistema): sar iostat vmstat 15- Para que sirven ‘/etc/lvm/backup’ y ‘/etc/lvm/archive’? Cuando creamos o actualizamos una partición basada en lvm, la copia de seguridad de los metadatos se guarda en '/etc/ lvm/backup', los nuevos metadatos se almacenan en '/etc/lvm/archive'. Como ves son archivos importantes, ademas si tienes algún problema con el comando vgcfgrestore puedes restaurar los metadatos del volumen. 16- Como listar las tablas de enrutamiento en linux? Para enumerar las tablas tenemos dos comandos ideales, son: netstat -nr #y route -n 17- Como puedo modificar el puerto SSH predeterminado en linux? Este tema también lo tratamos en profundidad en un articulo anterior, de todas maneras es así de fácil... nano /etc/ssh/sshd_config Edita donde pone "22", guarda el archivo y cierra el editor. No te olvides de conceder permisos al nuevo puerto. 18- Como puedo ver las marcas de tiempo en linux? En la mayoría de distribuciones linux puedes utilizar el comando dmesg (mensajes de diagnostico), con su correspondiente parámetro. dmesg -T 19- Como puedo saber la marca (fabricante) y el modelo de un servidor o estación de trabajo? Con el comando dmidecode, podemos averiguar la marca y el modelo del servidor. dmidecode -t system 20- Como identificar la bios del sistema? Para esto, también nos ayudamos del comando demidecode. dmidecode -t bios 21- Como extender un grupo de volúmenes ya creado? Lo primero que tenemos que hacer es crear el volumen físico (pv) en el nuevo disco (sin formato), en este caso /dev/sdb. pvcreate /dev/sdb Ahora ejecutamos vgextend. vgextend nombre-del-grupo-volumen /dev/sdb Esta es la ultima de la serie de preguntas a un sysadmin más comunes, evidentemente son muchas más, pero he seleccionado las que considero más útiles para los usuarios en general. Espero que este articulo te sea de utilidad, puedes ayudarnos a mantener el servidor con una donación (paypal), o también colaborar con el simple gesto de compartir nuestros artículos en tu sitio web, blog, foro o redes sociales. Preguntas a un sysadmin. Read the full article

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nisa7890 · 3 years ago

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nisa987 · 3 years ago

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computingpostcom · 3 years ago

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In this guide, I’m going to show you how to configure MongoDB Replica Set on Ubuntu 20.04|18.04|16.04 server. MongoDB is an enterprise-class NoSQL database system with auto-scaling, high availability and high performance. In a NoSQL database, data is stored in a document structure using MongoDB BSON format. SQL statements cannot be used in MongoDB to insert or retrieve data. What is MongoDB Replication / Replica set? In MongoDB, a replica set is a group of mongod processes that maintain the same data set. Replica sets are the basis for all production deployments as they provide data redundancy and high availability. This tutorial will describe the steps required to create a working three nodes replica set without configured access control to restrict access. This guide is based on below system IP Addresses: MongoDB Server1: 10.10.5.2 MongoDB Server2: 10.10.5.3 MongoDB Server3: 10.10.5.4 Step 1: Setup Requirements Before you can configure a replica set you’ve to install MongoDB on all the servers. Make sure correct hostnames are configured on the servers that will be used for replication. Set mapping for IP address and FQDNs locally on the servers if you don’t have a working DNS server. # Edit and set the values correctly 10.10.5.2 mongodb-01.example.net mongodb-01 10.10.5.3 mongodb-02.example.net mongodb-02 10.10.5.4 mongodb-03.example.net mongodb-03 Step 2: Install MongoDB on all Ubuntu 20.04|18.04 Nodes Follow below steps to install MongoDB on Ubuntu server. Update system: sudo apt-get update sudo apt-get upgrade && sudo reboot Import MongoDB public GPG Key: sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 9DA31620334BD75D9DCB49F368818C72E52529D4 Once the key has been imported, add the repository: ### Ubuntu 20.04 ### echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/4.4 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.4.list ### Ubuntu 18.04 ### echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.4 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.4.list ### Ubuntu 16.04 ### echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/4.4 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.4.list Install MongoDB packages sudo apt-get update sudo apt install -y mongodb-org Using Dedicated disk to store MongoDB data (Optional) For my setup, I have 10GB secondary storage dedicated for MongoDB data. I’ll partition it and mount to /data/mongodb. # lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 32G 0 disk |-sda1 8:1 0 487M 0 part /boot |-sda2 8:2 0 1.9G 0 part [SWAP] `-sda3 8:3 0 29.6G 0 part / vda 252:0 0 10G 0 disk Create a GPT partition table for the secondary disk, it can be more than one disk parted -s -a optimal -- /dev/vda mklabel gpt parted -s -a optimal -- /dev/vda mkpart primary 0% 100% parted -s -- /dev/vda align-check optimal 1 Then create LVM volume, this will make it easy to extend the partition $ sudo pvcreate /dev/vda1 Physical volume "/dev/vda1" successfully created. $ sudo vgcreate vg11 /dev/vda1 Volume group "vg11" successfully created $ sudo lvcreate -n data -l 100%FREE vg11 Logical volume "data" created Create a ext4filesystem on the Logical Volume created. $ sudo mkfs.ext4 /dev/mapper/vg11-data mke2fs 1.44.1 (24-Mar-2018) Creating filesystem with 2620416 4k blocks and 655360 inodes Filesystem UUID: b98e07e5-1b04-4282-a9db-fa5b73c74d2f Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 Allocating group tables: done Writing inode tables: done Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: done Create a mount point and mount the partition echo "/dev/mapper/vg11-data /data ext4 defaults 0 0" | sudo tee -a /etc/fstab

mkdir /data mount -a Confirm that the partition mount was successful: $ df -hT | grep /data /dev/mapper/vg11-data ext4 9.8G 37M 9.3G 1% /data Create a folder for MongoDB data sudo mkdir /data/mongodb sudo chown -R mongodb:mongodb /data/mongodb sudo chmod -R 775 /data/mongodb Configure the storage path to the one created earlier on all nodes $ sudo vim /etc/mongod.conf # Where and how to store data. storage: dbPath: /data/mongodb journal: enabled: true Step 3: Configure MongoDB Replica set Now that we have everything needed ready, let’s proceed to configure MongoDB replica set. Change MongoDB Listen Address from localhost IP on all nodes $ sudo vim /etc/mongod.conf # node 1 # network interfaces net: port: 27017 bindIp: 10.10.5.2 # Listen to local interface only, comment to listen on all interfaces. # node 2 # network interfaces net: port: 27017 bindIp: 10.10.5.3 # Listen to local interface only, comment to listen on all interfaces. # node 3 # network interfaces net: port: 27017 bindIp: 10.10.5.4 # Listen to local interface only, comment to listen on all interfaces. Configuring MongoDB Replica Set One of the MongoDB nodes run as the PRIMARY, and all other nodes will work as SECONDARY. Data is always to the PRIMARY node and the data sets are then replicated to all other SECONDARYnodes. Edit the MongoDB configuration file mongod.conf and enable replica set on all nodes replication: replSetName: "replica01" Open port 27017/tcp on the firewall: sudo ufw enable sudo ufw allow ssh sudo ufw allow 27017/tcp Configure MongoDB to start during the operating system’s boot sudo systemctl enable mongod.service sudo systemctl restart mongod.service Check the listen Address of MongoDB service: # ss -tunelp | grep -i mongo tcp LISTEN 0 128 10.10.5.2:27017 0.0.0.0:* users:(("mongod",pid=15288,fd=11)) uid:111 ino:46927 sk:4 Initiate MongoDB Replica Set Our MongoDB Node1 (mongodb-01) will be the PRIMARY and the other two will act as SECONDARY Login to the mongodb-01 server and start the mongo shell. $ mongo 10.10.5.2 MongoDB shell version v4.0.1 connecting to: mongodb://10.10.5.2:27017/test MongoDB server version: 4.0.1 Welcome to the MongoDB shell. For interactive help, type "help". ... > Initialize replica set on node1 by running below command: > rs.initiate() "info2" : "no configuration specified. Using a default configuration for the set", "me" : "10.10.5.2:27017", "ok" : 1, "operationTime" : Timestamp(1534797235, 1), "$clusterTime" : "clusterTime" : Timestamp(1534797235, 1), "signature" : "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) Make sure you get 1 for ok state Add secondary nodes replica01:PRIMARY> rs.add("mongodb-02") "ok" : 1, "operationTime" : Timestamp(1534797580, 1), "$clusterTime" : "clusterTime" : Timestamp(1534797580, 1), "signature" : "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) replica01:PRIMARY> rs.add("mongodb-03") "ok" : 1, "operationTime" : Timestamp(1534797614, 1), "$clusterTime" : "clusterTime" : Timestamp(1534797614, 1), "signature" : "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) Check replica set status using: replica01:PRIMARY> rs.status() Check the status of the master replica01:PRIMARY> rs.isMaster()

Testing MongoDB Replication Create a test database on mongodb-01 replica01:PRIMARY> use test_db switched to db test_db Add some data > db.test.save( "desc": "My Test Database", "apps": ["Test1", "Test2", "Test3", "Test4"], ) replica01:PRIMARY> show dbs admin 0.000GB config 0.000GB local 0.000GB test_db 0.000GB replica01:PRIMARY> use test_db switched to db test_db replica01:PRIMARY> show collections test Conclusion You now have a working MongoDB replication. You can increase the cluster size from three nodes to five nodes, seven nodes or more. This number is calculated from: [Master Eligible Nodes) / 2 + 1], which means an odd number of nodes is required for high availability, the minimum number is three. Reference: https://docs.mongodb.com/master/replication/ https://docs.mongodb.com/manual/tutorial/deploy-replica-set/

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globalmediacampaign · 4 years ago

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MySQL Backup and Recovery Best Practices

In this blog, we will review all the backup and restore strategies for MySQL, the cornerstones of any application. There are a few options, depending on your topology, MySQL versions, etc. And based on that, there are some questions we need to ask ourselves to make sure we make the right choices. How many backups we need to keep safe, or what’s the best retention policy for us? This means the number of backups to safeguard, whether local or remote (external fileserver, cloud). The retention policy can be daily, weekly, or monthly, depending on the free space available. What is the Recovery Time Objective? The Recovery Time Objective (RTO) refers to the amount of time that may pass during a disruption before it exceeds the maximum allowable threshold specified in the Business Continuity Plan. The key question related to RTO is, “How quickly must the data on this system be restored?” What is the Recovery Point Objective? The Recovery Point Objective (RPO) is the duration of time and service level within which a business process must be stored after a disaster in order to avoid unacceptable consequences associated with a break in continuity. The key question related to RPO is, “How much data can we lose?” Different Types of Backups There are two backup types: physical and logical. Physical (Percona XtraBackup, RDS/LVM Snapshots, MySQL Enterprise Backup), and also you can use cp or rsync command lines to copy the datadir as long as mysql is down/stopped. Logical (mysqldump, mydumper, mysqlpump, mysql shell only for mysql 8) Also is recommended to take a copy of binlog files, why? Well, this will help us to recover until the last transaction. Why are backups needed? Backups are needed in case of multiple problems: Host Failure: We can get multiple problems from disks stalled or broken disks. Also from cloud services, our DB instance can be broken and it’s non-accessible. Corrupted Data: This can happen on a power outage, MySQL wasn’t able to write correctly and close the file, sometimes when MySQL starts again it cannot start due to corrupted data and the crash recovery process cannot fix it. Inconsistent Data: When a human mistake, delete/update erroneous data over the primary or replica node. DataCenter Failure: power outage or internet provider issues. Legislation/Regulation: provide consistent business value and customer satisfaction. Now let me explain those different types of backups mentioned above, but before I continue, it’s important to configure a new and dedicated replica node for backups purposes, due to the high CPU load to avoid any issue on any other replica node (AKA backup server). Logical Backup This is a dump from logical database structure (CREATE DATABASE, CREATE TABLE statements) and content (INSERT statements). This is recommended to be used against smaller amounts of data. The disadvantage of this method is slower (backup and restore) if you compare it with physical backups. Using mydumper you can backup and restore a single database or a single table if it’s needed, and this is useful to copy some data to a different environment to run tests. Also, mydumper can take a consistent (as long as all the tables are InnoDB engine) backup and provides accurate master and slave log positions. The output is larger than for physical backup, particularly when saved in text format, but it can be compressed on the fly depending on the software you are using. Mydumper can compress and mysqldump needs to add a pipe to redirect the output to gzip, for example. Logical backups are used to address data corruption or the need to restore a subset of tables. Physical (Raw) Backup In short, this consists of exact copies of database directories and files. This can be a copy for all or a part from MySQL datadir directory. This kind of backup is most used to restore or create a new replica node easily and quickly and is used to address host failure. It’s recommended to restore using the same MySQL version. I recommend using Percona XtraBackup because it can include any related files such as configuration files like cnf config files. Snapshot Backups Some file system implementations enable “snapshots” to be taken. These provide logical copies of the file system at a given point in time, without requiring a physical copy of the entire file system. MySQL itself does not provide the capability for taking file system snapshots but it is available using third-party solutions such as LVM or ZFS. The disadvantage is that sometimes physical backups do not compress much, because data is usually in a binary format and sometimes the table is already compressed. Binary Log Backups Binlog backups specifically address RPO. Binary log files contain records of each SQL query executed that made changes. From MySQL 5.6 on, you can use mysqlbinlog to stream binary logs from a remote server. You can combine binlog backups with Percona XtraBackup or mydumper backup to allow restoration up to the end of the most-recently-backed-up binary log. Incremental / Differential Backups An incremental backup is a backup of everything that has changed since the last backup (a binary log backup is a special case of an incremental backup). This is a very good option if the dataset size is huge, as you can take a full backup at the beginning of the week and run incremental backups per day. Also, the backup size is smaller than the full backup. The main risks associated with incremental backups are: – A single corrupt incremental backup may invalidate all the others – Incremental backups typically negatively affect the RTO For a differential backup, it copies the differences from your last backup, and the advantage is that a lot of data does not change from one backup to the next, so the result can be significantly smaller backups. This saves disk space. Percona XtraBackup supports both incremental and differential backups. Offsite Storage It’s highly recommended to copy all the backup methods to another place, like the cloud or an external file server, so in case of host failure or data center failure, you have another copy. Not all the backup files need to be uploaded to the cloud, sometimes the time you need to spend in the download is bigger than the time consumed in the recovery process. A good approach is to keep 1-7 days locally on the backup server in case a fast recovery is needed, and this depends on your business regulations. Encryption Backups have sensitive data, so it’s highly recommended to encrypt, especially for offsite storage. This adds more time when you need to restore a backup but it keeps your data safe. GPG is a good option to encrypt backups, and if you use this option or some other alternative, don’t forget to get a copy of the keys/passphrase. If you lose it, your backups will be useless. Restore Testing Depending on your business, it’s highly recommended to test your backups at least once per month. This action validates your backups are not corrupted and it provides critical metrics on recovery time. This process should be automated to get the full backup, restore it, and finally configure this server as a replica from the current primary or another replica. This is good as well to validate that the replication process has no errors. Many customers are using this methodology to refresh their QA/STG environment to have fresh data from production backups. In addition to the above, it is recommended to create a manual or automated restore documentation process to keep all the steps together, so in case of disaster, you can follow it without wasting time. Retention Requirements Last but not least, it is very important to keep multiple copies of different backup types. Our best recommendation is: One or two physical backups locally on the backup server (as long as space allows it). Seven daily and four weekly logical backups locally on the backup server. 30 days of binlog backups locally on the backup server. For offsite backups (like S3, Google Cloud, etc.), keep monthly backups for one year or more. For local backups, keep in mind you will need a minimum of 2.5 times the current dataset size as free disk space to save/meet these retention policies. Don’t forget to encrypt all the backup types! Legal or regulatory requirements may also dictate how long data must be archived. Percona Can Help Percona can help you choose, implement, and optimize the most appropriate MySQL backup and recovery solution for your MySQL ecosystem. If your current solution unexpectedly fails, we can facilitate your recovery with onsite, remote, or emergency consulting services. We can also help you take steps to prevent another occurrence. Every situation is unique and we will work with you to create the most effective solution for your business. Contact Us https://www.percona.com/blog/2021/01/12/mysql-backup-and-recovery-best-practices/

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siva3155 · 6 years ago

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300+ TOP MariaDB Interview Questions and Answers

MariaDB Interview Questions for freshers experienced :-

1. What is MariaDB? It is a community based database devoloped by MySQL Devolopers. It provides same features as MySQL also, can be said that it is a replacement of MySQL. 2. Enlist some features of MariaDB. It supports different Programming Languages and can run on many Operating Systems. It provides Galera Cluster Technology. It has more storage engines. It has quicker and more transparent security release. 3. Write the default data directory for MariaDB? The location of data directory is controlled by datadir variable. The default address is /etc/mysql/my.cnf file where MariaDBis configured to store data. 4. What is Galera Cluster in MariaDB? Galera Cluster is a synchronous multi-master cluster for MariaDB but it is only for linux and only supports XtraDN/InnoDB. 5. Enlist some GUI/workbench for MariaDB. MySQL Workbench Webyog/SQLyog HeidiSQL dbForge Studio 6. Why does MariaDB 10.2 use InnoDB instead of XtraDB? Keeping upto date with Mysql, MariaDB uses InnoDB/XtraDB but it has becomes a very difficult task to devolop. Devolopment was already going on with InnoDB which has taken more than half a year. Thus, to release ASAP they didn’t switch to XtraDB. 7. What is an aggregate function? Aggregate function are those functions which grouped multiple rows data on some condition to provide more significant result such as List, Set, Group etc. 8. Enlist some types of aggregate function? COUNT Function SUM Function MIN Function MAX Function AVG Function 9. What are the different types of Clause used in MariaDB? Where Clause Order By Clause Like Clause Distinct Clause etc. 10. What is JOIN? How many types of JOIN in MariaDB? Join is used to retreive data from multiple tables by applieng joins such as: INNER JOIN LEFT OUTER JOIN RIGHT OUTER JOIN 11. What is the use of ORDER BY clause in MariaDB? ORDER BY clause is used to sort the records in inreasing or decreasing order. Syntax: SELECT expressions FROM tables ORDER BY expression ; 12. How MariaDB protects from SQL Injection? SQL Injection problem occurs at the time of Insertion or Updation of data such as Name, Salary etc and code logic fails to analyze. To avoid SQL Injection we can provide Validation through pattern matching. 13. Enlist the types of Backups in MariaDB. There are two types of Backups: Logical Backups: It provides flexibility of restoring data on another machines. Logical Backups occurs at tables and database. Physical Backups: This type of backups is smaller in size and vaery fast in restoring of data. It includes log and configuration files which occur at directory or file level. 14. Enlist some backup tools. XtraBackup Snapshots LVM TokuBackup 15. What is Indexs? How many types of Indexes in MariaDB? Indexes: It is a tools which helps in faster retreival of records present in tables. Indexes is of 4 types: Primary Unique Plain Full-Text 16. What are Heap tables? HEAP tables are present in memory and they are used for high speed storage on temporary basis. 17. Which Is The Max Storage Capacity Of Version 5.5 Mariadb? InnoDB/XtraDB tables can be up to 64TB (terabytes) in size. On top of this you can have multiple tables per database and multiple databases per server. 18. What are Heap tables? HEAP tables are present in memory and they are used for high speed storage on temporary basis. 19. What is function in MariaDB? MariaDB function is a stored program that is used to pass parameters into them and return a value. 20. What is the use of DELETE statement in MariaDB? The MariaDB DELETE statement is used to delete one or more records from the table in the database. 21. How can you retrieve limited number of records from a table? LIMIT clause is used with SELECT statement to select a limited number of records from a table. 22. What is a procedure or a stored procedure in database? Procedures are sort of functions in a database. Procedures are created when you want to perform a task repetitively. MariaDB procedure is a stored program that is used to pass parameters into it. It does not return a value like a function does. MariaDB Questions and Answers Pdf Download Read the full article

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usajobsite · 6 years ago

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Linux Administrator

JOB DESCRIPTION:<div> </div><div>Primary contribution involves being responsible for IT Infrastructure comprising of high end technology ,wherein the accountability will include 24x7 running of Linux/Unixx servers and VMware, consistent with established specifications and business requirements to deliver business value. The domain accountability includes Linux Server and VMware Administration. Familiar with ticketing tools in order to track down incidents and break fix request Familiar with client/server troubleshooting related to different type of servers [SendMail , FTP, SSH, Network etc. ] Automation and optimization of existing and prospective IT environment through scripting [Shell / Perl] Troubleshooting on virtual servers [ knowledge of vSphere /Virtual Center preferred] User Administration and Account Management LDAP. Clustering Technology is an added advantage [Veritas cluster (VCS) or RedHat Cluster]. Good knowledge on LVM/VxVM Monitoring daily backup and related issues [TSM would be preferred] Experience of working on NFS servers Good knowledge about SAN concepts, setting up, multi-pathing (device mapper) amp; troubleshooting SAN issues from the Linux OS side. Knowledge of Linux security amp; compliance is required. Periodic Quality Assurance/Server Hardening exercises for newly built servers. Able to troubleshoot servers through console [ Knowledge of ILO/RAS preferred] Skills on configuration of network and related services at operating system level like NFS,NIC Bonding, Sendmail, SSH and other TCP/IP services Involvement in periodic activities as Rapid Recovery [RR],Hardware amp; Firmware upgrade, OS Patching ,etc Good knowledge about UNIX system files, boot process and run levels Participate in On-Call and NOC duties on periodic basis. Well versed with ITIL concepts such as Incident, Change and Problem Management. </div> Linux-Administrator from Job Portal https://www.jobisite.com/ext/611553-Linux-Administrator

#Job Portal

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sololinuxes · 5 years ago

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Eliminar directorios vacíos con un script bash

Eliminar directorios vacíos con un script bash, en linux. A base de instalar y desinstalar aplicaciones, es común que nuestro sistema se llene de carpetas (directorios) vacías. Es cierto que ocupan poco espacio de nuestro disco, pero también es cierto que son muy molestas en ciertos momentos, por ejemplo cuando buscamos un archivo en particular, o listamos los directorios de nuestro sistema. En este artículo (de los que a mí me gustan), te presento un script bash con la capacidad de identificar los directorios vacíos y borrarlos (eliminar directorios vacios), si tú se lo pides. Es bastante seguro, dado que aparte que tienes que indicar donde buscar, también te solicita permiso. Deberás responder YES o NO.

Eliminar directorios vacíos con un script bash

Creamos nuestro script para eliminar directorios. nano borrard.sh Copia y pega el siguiente código. #!/bin/bash #Check if user input parameter, if not ask to enter directory if ; then #Ask user to input directory where to start search for empty directories. echo -n "Introduce el directorio donde quieres eliminar las carpetas vacías: " #we read input while read dir do #we check if input empty test -z "$dir" && { #if input empty – we ask once more to input directory echo -n "Introduce el directorio: " continue } #if entered no empty data – continue to do other things break done #if user entered parameter do next: else #dirname will be passed parameter dir=$1 fi #this check if directory exist, exit if not if ; then echo "Este directorio no existe" exit 1 fi #We will store list of all directories in temporary file DirList=/tmp/ditlist.tmp # we search for all directories find $dir -type d > $DirList #writing all directories to vatiable dirs=`cat $DirList` #start checking every directory for dir in $dirs do #we are checking if directory is empty || continue #this ask user if really delete directory echo -n "Quieres eliminar el directorio vacio $dir: " #reading users answer: read answer #Checing answer, if yes – we will delete folder, nothing in other case: if ; then rmdir "$dir" fi done Guarda el script y cierra el editor. Para no tener problemas de permisos, es recomendable que siempre ejecutes este script bash con privilegios de administrador. Ahora vemos un ejemplo real en un servidor demo, no reproduzcas la ruta o te quedarás sin sistema operativo. sudo bash borrard.sh Nos pregunta el directorio del sistema (o cualquier otro), donde queremos buscar y borrar los directorios que están vacíos. # sudo bash borrar.sh Introduce el directorio donde quieres eliminar las carpetas vacías: Como es un demo y somos más chulos que un ocho, borramos los directorios vacíos de "/etc" (no lo hagas, solo es una demo). Ten cuidado al eliminar directorios vacíos. Continuamos con nuestro ejemplo. # bash borrar.sh Introduce el directorio donde quieres eliminar las carpetas vacías: /etc Observa como borramos todos los directorios vacíos... # sudo bash borrar.sh Introduce el directorio donde quieres eliminar las carpetas vacías: /etc Quieres eliminar el directorio vacio /etc/smartmontools/smartd_warning.d: yes Quieres eliminar el directorio vacio /etc/tuned/recommend.d: yes Quieres eliminar el directorio vacio /etc/modules-load.d: yes Quieres eliminar el directorio vacio /etc/ppp/peers: y Quieres eliminar el directorio vacio /etc/xdg/autostart: yes Quieres eliminar el directorio vacio /etc/selinux/targeted/logins: yes Quieres eliminar el directorio vacio /etc/selinux/targeted/active/modules/disabled: yes Quieres eliminar el directorio vacio /etc/selinux/targeted/modules/active/modules: yes Quieres eliminar el directorio vacio /etc/selinux/tmp: yes Quieres eliminar el directorio vacio /etc/selinux/final: yes Quieres eliminar el directorio vacio /etc/multipath: yes Quieres eliminar el directorio vacio /etc/gnupg: yes Quieres eliminar el directorio vacio /etc/gss/mech.d: yes Quieres eliminar el directorio vacio /etc/skel: yes rmdir: fallo al borrar «/etc/skel»: El directorio no está vacío Quieres eliminar el directorio vacio /etc/tmpfiles.d: yes Quieres eliminar el directorio vacio /etc/systemd/user: yes Quieres eliminar el directorio vacio /etc/udev/rules.d: yes Quieres eliminar el directorio vacio /etc/krb5.conf.d: yes Quieres eliminar el directorio vacio /etc/dracut.conf.d: yes Quieres eliminar el directorio vacio /etc/lvm/archive: yes Quieres eliminar el directorio vacio /etc/lvm/cache: yes Quieres eliminar el directorio vacio /etc/lvm/backup: yes Quieres eliminar el directorio vacio /etc/xinetd.d: yes Quieres eliminar el directorio vacio /etc/glvnd/egl_vendor.d: yes Quieres eliminar el directorio vacio /etc/sysconfig/console: yes Quieres eliminar el directorio vacio /etc/sysconfig/modules: yes Quieres eliminar el directorio vacio /etc/chkconfig.d: yes # # Eliminar directorios vacios Al recorrer todo el árbol de directorios indicado, el sistema volverá al usuario. Ten mucho cuidado al eliminar directorios, algunos pueden ser necesarios para un correcto funcionamiento del sistema. Canales de Telegram: Canal SoloLinux – Canal SoloWordpress Espero que este artículo te sea de utilidad, puedes ayudarnos a mantener el servidor con una donación (paypal), o también colaborar con el simple gesto de compartir nuestros artículos en tu sitio web, blog, foro o redes sociales. Eliminar directorios vacíos con un script bash. Read the full article

#/etc #bash #directorios #directoriosvacíos #eliminar #Eliminardirectorios #script #scriptbash

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ameliamike90 · 7 years ago

Text

Linux Administrator (six months Internship) job at SoftSolvers Solutions Malaysia

We are on a mission to create a tech Unicorn from Malaysia and are looking for the best in class people to join us in this mission!!

Second CRM

Second CRM is our core business automation solution designed to make medium to large corporations more productive by automating their operations using Internet and mobile technologies. We champion smoother digital transformation using incremental automation of business processes as opposed to large scale disruptive change.

Second CRM focuses on improving all business functions, right from Sales, Marketing, Customer Service, Operations to even Billing and Payments and it easily fits in to most business environments by being flexible, cost effective and easy to use application.

High Growth Phase

We are actively looking to hire creative bright talents to join us, as Developers [PHP/MySQL, Android, iOS], Designers [web and mobile UI], Project Manager / Business Analysts, Product Managers, Sales [Inside sales and business dev], Marketing [Social Media, Content writer, full stack Marketing], Finance [Accounting, International taxation] and so many more.

SoftSolvers is headquartered in Singapore and has operations in Singapore and Malaysia.

SoftSolvers Research & Development Centre and Regional Support Center is based in Cyberjaya, in CBD Perdana area, near D'Pulze Mall and lot of food eatries and entertainment zones.

Installing and Configuring CentOS 6.x / 7.x

Installing PHP, Apache and MySQL using yum and configuring [php.ini, httpd.conf and my.cnf]

Upgrade/Downgrade versions of PHP, Apache and MySQL

General administrative tasks in Linux (iptables, cron, LVM, partitioning, rsync, etc)

General administrative tasks in MySQL (backups, restore, indexing, logs, etc)

Working with developers to troubleshot and solve server related issues

Server Security, Performance and Scalability are desirable skills but can learn in coming months

Hosting and Managing servers on Amazon (AWS) is desirable skill but can learn in coming months

Who we are looking for

Candidate must possess or currently pursuing a Diploma, Degree in IT/Computer Science or equivalent.

Able to work independently, good research on Internet to solve technical issues and not afraid of working late nights, weekends and at all odd hours

Strong oral and written communication skills in English, teamwork, organization, and attention to detail

Able to work in Cyberjaya and a minimum of six months internship

StartUp Jobs Asia - Startup Jobs in Singapore , Malaysia , HongKong ,Thailand from http://www.startupjobs.asia/job/41274-linux-administrator-six-months-internship-software-system-admin-job-at-softsolvers-solutions-malaysia Startup Jobs Asia https://startupjobsasia.tumblr.com/post/179855368069

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shuying877 · 7 years ago

Text

Linux Administrator (six months Internship) job at SoftSolvers Solutions Malaysia

We are on a mission to create a tech Unicorn from Malaysia and are looking for the best in class people to join us in this mission!!

Second CRM

High Growth Phase

SoftSolvers is headquartered in Singapore and has operations in Singapore and Malaysia.

SoftSolvers Research & Development Centre and Regional Support Center is based in Cyberjaya, in CBD Perdana area, near D'Pulze Mall and lot of food eatries and entertainment zones.

Installing and Configuring CentOS 6.x / 7.x

Installing PHP, Apache and MySQL using yum and configuring [php.ini, httpd.conf and my.cnf]

Upgrade/Downgrade versions of PHP, Apache and MySQL

General administrative tasks in Linux (iptables, cron, LVM, partitioning, rsync, etc)

General administrative tasks in MySQL (backups, restore, indexing, logs, etc)

Working with developers to troubleshot and solve server related issues

Server Security, Performance and Scalability are desirable skills but can learn in coming months

Hosting and Managing servers on Amazon (AWS) is desirable skill but can learn in coming months

Who we are looking for

Candidate must possess or currently pursuing a Diploma, Degree in IT/Computer Science or equivalent.

Able to work independently, good research on Internet to solve technical issues and not afraid of working late nights, weekends and at all odd hours

Strong oral and written communication skills in English, teamwork, organization, and attention to detail

Able to work in Cyberjaya and a minimum of six months internship

From http://www.startupjobs.asia/job/41274-linux-administrator-six-months-internship-software-system-admin-job-at-softsolvers-solutions-malaysia

from https://startupjobsasiablog.wordpress.com/2018/11/07/linux-administrator-six-months-internship-job-at-softsolvers-solutions-malaysia-2/

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startupjobsasia · 7 years ago

Text

Linux Administrator (six months Internship) job at SoftSolvers Solutions Malaysia

We are on a mission to create a tech Unicorn from Malaysia and are looking for the best in class people to join us in this mission!!

Second CRM

High Growth Phase

SoftSolvers is headquartered in Singapore and has operations in Singapore and Malaysia.

SoftSolvers Research & Development Centre and Regional Support Center is based in Cyberjaya, in CBD Perdana area, near D'Pulze Mall and lot of food eatries and entertainment zones.

Installing and Configuring CentOS 6.x / 7.x

Installing PHP, Apache and MySQL using yum and configuring [php.ini, httpd.conf and my.cnf]

Upgrade/Downgrade versions of PHP, Apache and MySQL

General administrative tasks in Linux (iptables, cron, LVM, partitioning, rsync, etc)

General administrative tasks in MySQL (backups, restore, indexing, logs, etc)

Working with developers to troubleshot and solve server related issues

Server Security, Performance and Scalability are desirable skills but can learn in coming months

Hosting and Managing servers on Amazon (AWS) is desirable skill but can learn in coming months

Who we are looking for

Candidate must possess or currently pursuing a Diploma, Degree in IT/Computer Science or equivalent.

Able to work independently, good research on Internet to solve technical issues and not afraid of working late nights, weekends and at all odd hours

Strong oral and written communication skills in English, teamwork, organization, and attention to detail

Able to work in Cyberjaya and a minimum of six months internship

0 notes

marlik-job-blog · 8 years ago

Text

New Post has been published on مارلیک | اخبار و تازه های استخدامی

New Post has been published on http://job.marlik.ir/news/%d8%a7%d8%b3%d8%aa%d8%ae%d8%af%d8%a7%d9%85-%db%b1%db%b1-%d8%b1%d8%af%db%8c%d9%81-%d8%b4%d8%ba%d9%84%db%8c-%d8%af%d8%b1-%d8%b4%d8%b1%da%a9%d8%aa-%d9%be%d8%b1%d8%af%d8%a7%d8%b2%d8%b4%da%af%d8%b1%d8%a7/

استخدام ۱۱ ردیف شغلی در شرکت پردازشگران سامان

شرکت پردازشگران سامان در راستای تکمیل کادر پرسنلی خود از واجدین شرایط در ردیفهای شغلی زیر در تهران دعوت به همکاری می‌نماید.

ردیف عنوان شغل مهارت تخصصی مهارت فنی ۱ برنامه نویس جاوا

-At least 3 years of experience in solution, design and development of web-based applications using Java/J2EE, Java Servlets, JSP, EJB3, Primefaces/JSF, XML, and Struts

-Very strong understanding of the OOAD concepts and able to use it in the low level design

-Experience in developing SOAP (JAX-WS) and RESTful (JAX-RS) Web Services using Spring Web Serviceو , Apache CXF, Jersey and Axis

-Important Spring Modules like Core, Context, DAO, ORM, AO, WEB-MVC, Security …

-Strong Back End experience to develop Data Layer using at least one of the ORM frameworks like Hibernate, JPA etc

-Experience in web based application Servers, WebLogic, Websphere and Apache Tomcat

-Continuous integration (Jenkins, Maven, Gradle, Ant, Bamboo/Hudson, SVN, Git)

-Strive to constantly improve the application development processes and tools

-Expert in tuning all tiers of applications on JEE platform and experience in implementing J2EE Design Patterns for module designs

-Experience in using JMS Queue and Topic’s

-Experience with IDEs like Eclipse, JDeveloper, IntelliJ, Spring Suite etc

-Bachelor’s degree in Computer Science or Engineering or equivalent working experience

-Application of software development principles, theories, concepts, and techniques

-Provides resolutions to an assortment of technical problems

-Innovative in providing solutions, likes to take on challenges with calculated risks

-Understand Business Requirements; participates in System Requirement Analysis; design Applications based on System Requirements and Architecture, prototype if necessary, develop, unit test and deploy application. Will use MS Visio, UML, RUP, and Agile Methodology

-Hands-on experience with build and deployment tools and languages

-Good knowledge of database concepts with working knowledge on SQL, SQL Server, Oracle, DB2 or Sybase database, and Stored Procedures

-Improve and expand Test Driven Development (TDD & ATDD / BDD) Approach to development

-Strong understanding of Service Oriented Architecture (SOA) and service design concepts

۲ برنامه نویس دات نت

-C# .Net

-OOP

-MVC

-Angular

-Wcf & WebServices

-WF

-Entity Framework & LINQ